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* Kprobes: The ON/OFF knob thru debugfsAnanth N Mavinakayanahalli2007-05-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch provides a debugfs knob to turn kprobes on/off o A new file /debug/kprobes/enabled indicates if kprobes is enabled or not (default enabled) o Echoing 0 to this file will disarm all installed probes o Any new probe registration when disabled will register the probe but not arm it. A message will be printed out in such a case. o When a value 1 is echoed to the file, all probes (including ones registered in the intervening period) will be enabled o Unregistration will happen irrespective of whether probes are globally enabled or not. o Update Documentation/kprobes.txt to reflect these changes. While there also update the doc to make it current. We are also looking at providing sysrq key support to tie to the disabling feature provided by this patch. [akpm@linux-foundation.org: Use bool like a bool!] [akpm@linux-foundation.org: add printk facility levels] [cornelia.huck@de.ibm.com: Add the missing arch_trampoline_kprobe() for s390] Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kprobes: kretprobes simplificationsChristoph Hellwig2007-05-08
| | | | | | | | | | | | | | | | | - consolidate duplicate code in all arch_prepare_kretprobe instances into common code - replace various odd helpers that use hlist_for_each_entry to get the first elemenet of a list with either a hlist_for_each_entry_save or an opencoded access to the first element in the caller - inline add_rp_inst into it's only remaining caller - use kretprobe_inst_table_head instead of opencoding it Signed-off-by: Christoph Hellwig <hch@lst.de> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Kprobes: print details of kretprobe on assertion failureAnanth N Mavinakayanahalli2007-05-08
| | | | | | | | | | | | | | | | | | In certain cases like when the real return address can't be found or when the number of tracked calls to a kretprobed function is less than the number of returns, we may not be able to find the correct return address after processing a kretprobe. Currently we just do a BUG_ON, but no information is provided about the actual failing kretprobe. Print out details of the kretprobe before calling BUG(). Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: Maneesh Soni <maneesh@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* move die notifier handling to common codeChristoph Hellwig2007-05-08
| | | | | | | | | | | | | | | | | | | | | | | This patch moves the die notifier handling to common code. Previous various architectures had exactly the same code for it. Note that the new code is compiled unconditionally, this should be understood as an appel to the other architecture maintainer to implement support for it aswell (aka sprinkling a notify_die or two in the proper place) arm had a notifiy_die that did something totally different, I renamed it to arm_notify_die as part of the patch and made it static to the file it's declared and used at. avr32 used to pass slightly less information through this interface and I brought it into line with the other architectures. [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: fix vmalloc_sync_all bustage] [bryan.wu@analog.com: fix vmalloc_sync_all in nommu] Signed-off-by: Christoph Hellwig <hch@lst.de> Cc: <linux-arch@vger.kernel.org> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Bryan Wu <bryan.wu@analog.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] i386: Kprobe rpl fixZachary Amsden2007-02-13
| | | | | | | | | Kprobes bugfix for paravirt compatibility - RPL on the CS when inserting BPs must match running kernel. Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de> CC: Eric Biederman <ebiederm@xmission.com>
* [PATCH] i386: Convert i386 PDA code to use %fsJeremy Fitzhardinge2007-02-13
| | | | | | | | | | | | | | | | | | | | | | | | | | | Convert the PDA code to use %fs rather than %gs as the segment for per-processor data. This is because some processors show a small but measurable performance gain for reloading a NULL segment selector (as %fs generally is in user-space) versus a non-NULL one (as %gs generally is). On modern processors the difference is very small, perhaps undetectable. Some old AMD "K6 3D+" processors are noticably slower when %fs is used rather than %gs; I have no idea why this might be, but I think they're sufficiently rare that it doesn't matter much. This patch also fixes the math emulator, which had not been adjusted to match the changed struct pt_regs. [frederik.deweerdt@gmail.com: fixit with gdb] [mingo@elte.hu: Fix KVM too] Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Ian Campbell <Ian.Campbell@XenSource.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Zachary Amsden <zach@vmware.com> Cc: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org>
* [PATCH] kprobes: enable booster on the preemptible kernelMasami Hiramatsu2006-12-07
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When we are unregistering a kprobe-booster, we can't release its instruction buffer immediately on the preemptive kernel, because some processes might be preempted on the buffer. The freeze_processes() and thaw_processes() functions can clean most of processes up from the buffer. There are still some non-frozen threads who have the PF_NOFREEZE flag. If those threads are sleeping (not preempted) at the known place outside the buffer, we can ensure safety of freeing. However, the processing of this check routine takes a long time. So, this patch introduces the garbage collection mechanism of insn_slot. It also introduces the "dirty" flag to free_insn_slot because of efficiency. The "clean" instruction slots (dirty flag is cleared) are released immediately. But the "dirty" slots which are used by boosted kprobes, are marked as garbages. collect_garbage_slots() will be invoked to release "dirty" slots if there are more than INSNS_PER_PAGE garbage slots or if there are no unused slots. Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "bibo,mao" <bibo.mao@intel.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Yumiko Sugita <yumiko.sugita.yf@hitachi.com> Cc: Satoshi Oshima <soshima@redhat.com> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kretprobe: fix kretprobe-booster to save regs and set statusMasami Hiramatsu2006-11-08
| | | | | | | | | | | | | | | | There are two bugs in the kretprobe-booster. 1) It doesn't make room for gs registers. 2) It doesn't change status of the current kprobe. This status will effect the fault handling. This patch fixes these bugs and, additionally, saves skipped registers for compatibility with the original kretprobe. Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kretprobe spinlock deadlock patchbibo,mao2006-10-02
| | | | | | | | | | | | kprobe_flush_task() possibly calls kfree function during holding kretprobe_lock spinlock, if kfree function is probed by kretprobe that will incur spinlock deadlock. This patch moves kfree function out scope of kretprobe_lock. Signed-off-by: bibo, mao <bibo.mao@intel.com> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe whitespace cleanupbibo,mao2006-10-02
| | | | | | | | | | | Whitespace is used to indent, this patch cleans up these sentences by kernel coding style. Signed-off-by: bibo, mao <bibo.mao@intel.com> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe-booster: disable in preemptible kernelMasami Hiramatsu2006-07-31
| | | | | | | | | | | | | | | | The kprobe-booster's safety check against preemption does not work well now, because the preemption count has been modified by read_rcu_lock() in atomic_notifier_call_chain() before we check it. So, I'd like to prevent boosting kprobe temporarily if the kernel is preemptable. Now we are searching for the good solution. Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Remove obsolete #include <linux/config.h>Jörn Engel2006-06-30
| | | | | Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de> Signed-off-by: Adrian Bunk <bunk@stusta.de>
* [PATCH] Kprobe: multi kprobe posthandler for boostermao, bibo2006-06-26
| | | | | | | | | | | | | | | | | | | | | | If there are multi kprobes on the same probepoint, there will be one extra aggr_kprobe on the head of kprobe list. The aggr_kprobe has aggr_post_handler/aggr_break_handler whether the other kprobe post_hander/break_handler is NULL or not. This patch modifies this, only when there is one or more kprobe in the list whose post_handler is not NULL, post_handler of aggr_kprobe will be set as aggr_post_handler. [soshima@redhat.com: !CONFIG_PREEMPT fix] Signed-off-by: bibo, mao <bibo.mao@intel.com> Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Satoshi Oshima <soshima@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe: boost 2byte-opcodes on i386Masami Hiramatsu2006-06-26
| | | | | | | | | | | | | | | | | | Previous kprobe-booster patch has not handled any 2byte opcodes and prefixes. I checked whole IA32 opcode map and classified it. This patch enables kprobe to boost those 2byte opcodes and prefixes. Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp> Cc: Satoshi Oshima <soshima@redhat.com> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] i386: don't try kprobes for v8086 modeZachary Amsden2006-06-23
| | | | | | | | | | | | Never allow int3 traps from V8086 mode to enter the kprobes handler. Signed-off-by: Zachary Amsden <zach@vmware.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe: fix resume execution on i386Masami Hiramatsu2006-04-28
| | | | | | | | | | | | | | | | Fix resume_execution() to handle iret and absolute jump opcode correctly on i386. Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp> Cc: Satoshi Oshima <soshima@redhat.com> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe cleanup for VM_MASK judgementmao, bibo2006-04-28
| | | | | | | | | | | | | | | | | | When trap happens in user space, kprobe_exceptions_notify() funtion will skip it. This patch deletes some unnecessary code for VM_MASK judgement in eflags. Signed-off-by: bibo, mao <bibo.mao@intel.com> Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp> Cc: Satoshi Oshima <soshima@redhat.com> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Switch Kprobes inline functions to __kprobes for i386Prasanna S Panchamukhi2006-04-19
| | | | | | | | | | | | | | | Andrew Morton pointed out that compiler might not inline the functions marked for inline in kprobes. There-by allowing the insertion of probes on these kprobes routines, which might cause recursion. This patch removes all such inline and adds them to kprobes section there by disallowing probes on all such routines. Some of the routines can even still be inlined, since these routines gets executed after the kprobes had done necessay setup for reentrancy. Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: fix broken fault handling for i386Prasanna S Panchamukhi2006-03-26
| | | | | | | | | | | | | | | | | | Provide proper kprobes fault handling, if a user-specified pre/post handlers tries to access user address space, through copy_from_user(), get_user() etc. The user-specified fault handler gets called only if the fault occurs while executing user-specified handlers. In such a case user-specified handler is allowed to fix it first, later if the user-specifed fault handler does not fix it, we try to fix it by calling fix_exception(). The user-specified handler will not be called if the fault happens when single stepping the original instruction, instead we reset the current probe and allow the system page fault handler to fix it up. Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobe handler: discard user space trapbibo,mao2006-03-26
| | | | | | | | | | | | | | Currently kprobe handler traps only happen in kernel space, so function kprobe_exceptions_notify should skip traps which happen in user space. This patch modifies this, and it is based on 2.6.16-rc4. Signed-off-by: bibo mao <bibo.mao@intel.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: <hiramatu@sdl.hitachi.co.jp> Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kretprobe: kretprobe-boosterMasami Hiramatsu2006-03-26
| | | | | | | | | | | | | | | | | | | | | | In normal operation, kretprobe makes a target function return to trampoline code. A kprobe (called trampoline_probe) has been inserted in the trampoline code. When the kernel hits this kprobe, it calls kretprobe's handler and it returns to the original return address. Kretprobe-booster removes the trampoline_probe. It allows the trampoline code to call kretprobe's handler directly instead of invoking kprobe. The trampoline code returns to the original return address. (changelog from Chuck Ebbert <76306.1226@compuserve.com> - thanks ;)) Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] x86: kprobes-boosterMasami Hiramatsu2006-03-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Current kprobe copies the original instruction at the probe point and replaces it with a breakpoint instruction (int3). When the kernel hits the probe point, kprobe handler is invoked. And the copied instruction is single-step executed on the copied buffer (not on the original address) by kprobe. After that, the kprobe checks registers and modify it (if need) as if the instructions was executed on the original address. My proposal is based on the fact there are many instructions which do NOT require the register modification after the single-step execution. When the copied instruction is a kind of them, kprobe just jumps back to the next instruction after single-step execution. If so, why don't we execute those instructions directly? With kprobe-booster patch, kprobes will execute a copied instruction directly and (if need) jump back to original code. This direct execution is executed when the kprobe don't have both post_handler and break_handler, and the copied instruction can be executed directly. I sorted instructions which can be executed directly or not; - Call instructions are NG(can not be executed directly). We should correct the return address pushed into top of stack. - Indirect instructions except for absolute indirect-jumps are NG. Those instructions changes EIP randomly. We should check EIP and correct it. - Instructions that change EIP beyond the range of the instruction buffer are NG. - Instructions that change EIP to tail 5 bytes of the instruction buffer (it is the size of a jump instruction). We must write a jump instruction which backs to original kernel code in the instruction buffer. - Break point instruction is NG. We should not touch EIP and pass to other handlers. - Absolute direct/indirect jumps are OK.- Conditional Jumps are NG. - Halt and software-interruptions are NG. Because it will stay on the instruction buffer of kprobes. - Prefixes are NG. - Unknown/reserved opcode is NG. - Other 1 byte instructions are OK. But those instructions need a jump back code. - 2 bytes instructions are mapped sparsely. So, in this release, this patch don't boost those instructions. >From Intel's IA-32 opcode map described in IA-32 Intel Architecture Software Developer's Manual Vol.2 B, I determined that following opcodes are not boostable. - 0FH (2byte escape) - 70H - 7FH (Jump on condition) - 9AH (Call) and 9CH (Pushf) - C0H-C1H (Grp 2: includes reserved opcode) - C6H-C7H (Grp11: includes reserved opcode) - CCH-CEH (Software-interrupt) - D0H-D3H (Grp2: includes reserved opcode) - D6H (Reserved) - D8H-DFH (Coprocessor) - E0H-E3H (loop/conditional jump) - E8H (Call) - F0H-F3H (Prefixes and reserved) - F4H (Halt) - F6H-F7H (Grp3: includes reserved opcode) - FEH-FFH(Grp4,5: includes reserved opcode) Kprobe-booster checks whether target instruction can be boosted (can be executed directly) at arch_copy_kprobe() function. If the target instruction can be boosted, it clears "boostable" flag. If not, it sets "boostable" flag -1. This is disabled status. In resume_execution() function, If "boostable" flag is cleared, kprobe-booster measures the size of the target instruction and sets "boostable" flag 1. In kprobe_handler(), kprobe checks the "boostable" flag. If the flag is 1, it resets current kprobe and executes instruction buffer directly instead of single stepping. When unregistering a boosted kprobe, it calls synchronize_sched() after "int3" is removed. So we can ensure followings after the synchronize_sched() called. - interrupt handlers are finished on all CPUs. - instruction buffer is not executed on all CPUs. And we can release the boosted kprobe safely. And also, on preemptible kernel, the booster is not enabled where the kernel preemption is enabled. So, there are no preempted threads on the instruction buffer. The description of kretprobe-booster: ==================================== In the normal operation, kretprobe make a target function return to trampoline code. And a kprobe (called trampoline_probe) have been inserted at the trampoline code. When the kernel hits this kprobe, it calls kretprobe's handler and it returns to original return address. Kretprobe-booster patch removes the trampoline_probe. It allows the trampoline code to call kretprobe's handler directly instead of invoking kprobe. And tranpoline code returns to original return address. This new trampoline code stores and restores registers, so the kretprobe handler is still able to access those registers. Current kprobe has about 1.3 usec/probe(*) overhead, and kprobe-booster patch reduces it to 0.6 usec/probe(*). Also current kretprobe has about 2.0 usec/probe(*) overhead. Kprobe-booster patch reduces it to 1.3 usec/probe(*), and the combination of both kprobe-booster patch and kretprobe-booster patch reduces it to 0.9 usec/probe(*). I expect the combination of both patches can reduce half of a probing overhead. Performance numbers strongly depend on the processor model. Andrew Morton wrote: > These preempt tricks look rather nasty. Can you please describe what the > problem is, precisely? And how this code avoids it? Perhaps we can find > something cleaner. The problem is how to remove the copied instructions of the kprobe *safely* on the preemptable kernel (CONFIG_PREEMPT=y). Kprobes basically executes the following actions; (1)int3 (2)preempt_disable() (3)kprobe_prehandler() (4)copied instructioin(single step) (5)kprobe_posthandler() (6)preempt_enable() (7)return to the original code During the execution of copied instruction, preemption is disabled (from step (2) to (6)). When unregistering the probes, Kprobe waits for RCU quiescent state by using synchronize_sched() after removing int3 instruction. Thus we can ensure the copied instruction is not executed. On the other hand, kprobe-booster executes the following actions; (1)int3 (2)preempt_disable() (3)kprobe_prehandler() (4)preempt_enable() <-- this one is added by my patch (5)copied instruction(direct execution) (6)jmp back to the original code The problem is that we have no way to prevent preemption on step (5) or (6). We cannot call preempt_disable() after step (6), because there are no rooms to do that. Thus, some other processes may be preempted at step(5) or (6) on preemptable kernel. And I couldn't find the easy way to ensure that other processes' stack do *not* have the address of them. (I thought some way to do that, but those are very costly.) So currently, I simply boost the kprobe only when the probe point is already preemption disabled. > Also, the patch adds a preempt_enable() but I don't see a corresponding > preempt_disable(). Am I missing something? It is corresponding to the preempt_disable() in the top of kprobe_handler(). I copied the code of kprobe_handler() here: static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; int ret = 0; kprobe_opcode_t *addr = NULL; unsigned long *lp; struct kprobe_ctlblk *kcb; /* * We don't want to be preempted for the entire * duration of kprobe processing */ preempt_disable(); <-- HERE kcb = get_kprobe_ctlblk(); Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: clean up resume_execute()Masami Hiramatsu2006-03-26
| | | | | | | | | | | | Clean up kprobe's resume_execute() for i386 arch. Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sem2mutex: kprobesIngo Molnar2006-03-23
| | | | | | | | | | | | Semaphore to mutex conversion. The conversion was generated via scripts, and the result was validated automatically via a script as well. Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes causes NX protection fault on i686 SMPPrasanna S Panchamukhi2006-02-24
| | | | | | | | | | | | | Fix a problem seen on i686 machine with NX support where the instruction could not be single stepped because of NX bit set on the memory pages allocated by kprobes module. This patch provides allocation of instruction solt so that the processor can execute the instruction from that location similar to x86_64 architecture. Thanks to Bibo and Masami for testing this patch. Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: fix race in recovery of reentrant probeKeshavamurthy Anil S2006-01-11
| | | | | | | | | | | | | | | | | There is a window where a probe gets removed right after the probe is hit on some different cpu. In this case probe handlers can't find a matching probe instance related to break address. In this case we need to read the original instruction at break address to see if that is not a break/int3 instruction and recover safely. Previous code had a bug where we were not checking for the above race in case of reentrant probes and the below patch fixes this race. Tested on IA64, Powerpc, x86_64. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: arch_remove_kprobeAnil S Keshavamurthy2006-01-10
| | | | | | | | | | | | | Currently arch_remove_kprobes() is only implemented/required for x86_64 and powerpc. All other architecture like IA64, i386 and sparc64 implementes a dummy function which is being called from arch independent kprobes.c file. This patch removes the dummy functions and replaces it with #define arch_remove_kprobe(p, s) do { } while(0) Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: changed from using spinlock to mutexAnil S Keshavamurthy2006-01-10
| | | | | | | | | | | | | | | Since Kprobes runtime exception handlers is now lock free as this code path is now using RCU to walk through the list, there is no need for the register/unregister{_kprobe} to use spin_{lock/unlock}_isr{save/restore}. The serialization during registration/unregistration is now possible using just a mutex. In the above process, this patch also fixes a minor memory leak for x86_64 and powerpc. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: increment kprobe missed count for multiprobesKeshavamurthy Anil S2005-12-12
| | | | | | | | | | | | | | When multiple probes are registered at the same address and if due to some recursion (probe getting triggered within a probe handler), we skip calling pre_handlers and just increment nmissed field. The below patch make sure it walks the list for multiple probes case. Without the below patch we get incorrect results of nmissed count for multiple probe case. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes: preempt_disable/enable() simplificationAnanth N Mavinakayanahalli2005-11-07
| | | | | | | | | | | Reorganize the preempt_disable/enable calls to eliminate the extra preempt depth. Changes based on Paul McKenney's review suggestions for the kprobes RCU changeset. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes: Use RCU for (un)register synchronization - arch changesAnanth N Mavinakayanahalli2005-11-07
| | | | | | | | | | | | Changes to the arch kprobes infrastructure to take advantage of the locking changes introduced by usage of RCU for synchronization. All handlers are now run without any locks held, so they have to be re-entrant or provide their own synchronization. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes: Track kprobe on a per_cpu basis - i386 changesAnanth N Mavinakayanahalli2005-11-07
| | | | | | | | | | | I386 changes to track kprobe execution on a per-cpu basis. We now track the kprobe state machine independently on each cpu, using an arch specific kprobe control block. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes: rearrange preempt_disable/enable() callsAnanth N Mavinakayanahalli2005-11-07
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following set of patches are aimed at improving kprobes scalability. We currently serialize kprobe registration, unregistration and handler execution using a single spinlock - kprobe_lock. With these changes, kprobe handlers can run without any locks held. It also allows for simultaneous kprobe handler executions on different processors as we now track kprobe execution on a per processor basis. It is now necessary that the handlers be re-entrant since handlers can run concurrently on multiple processors. All changes have been tested on i386, ia64, ppc64 and x86_64, while sparc64 has been compile tested only. The patches can be viewed as 3 logical chunks: patch 1: Reorder preempt_(dis/en)able calls patches 2-7: Introduce per_cpu data areas to track kprobe execution patches 8-9: Use RCU to synchronize kprobe (un)registration and handler execution. Thanks to Maneesh Soni, James Keniston and Anil Keshavamurthy for their review and suggestions. Thanks again to Anil, Hien Nguyen and Kevin Stafford for testing the patches. This patch: Reorder preempt_disable/enable() calls in arch kprobes files in preparation to introduce locking changes. No functional changes introduced by this patch. Signed-off-by: Ananth N Mavinakayahanalli <ananth@in.ibm.com> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: fix bug when probed on task and isr functionsKeshavamurthy Anil S2005-09-07
| | | | | | | | | | | | | | | | This patch fixes a race condition where in system used to hang or sometime crash within minutes when kprobes are inserted on ISR routine and a task routine. The fix has been stress tested on i386, ia64, pp64 and on x86_64. To reproduce the problem insert kprobes on schedule() and do_IRQ() functions and you should see hang or system crash. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: fix handling of simultaneous probe hit/unregisterJim Keniston2005-09-07
| | | | | | | | | | | | | | | | | | | | | | | This patch fixes a bug in kprobes's handling of a corner case on i386 and x86_64. On an SMP system, if one CPU unregisters a kprobe just after another CPU hits that probepoint, kprobe_handler() on the latter CPU sees that the kprobe has been unregistered, and attempts to let the CPU continue as if the probepoint hadn't been hit. The bug is that on i386 and x86_64, we were neglecting to set the IP back to the beginning of the probed instruction. This could cause an oops or crash. This bug doesn't exist on ppc64 and ia64, where a breakpoint instruction leaves the IP pointing to the beginning of the instruction. I don't know about sparc64. (Dave, could you please advise?) This fix has been tested on i386 and x86_64 SMP systems. To reproduce the problem, set one CPU to work registering and unregistering a kprobe repeatedly, and another CPU pounding the probepoint in a tight loop. Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: prevent possible race conditions i386 changesPrasanna S Panchamukhi2005-09-07
| | | | | | | | | This patch contains the i386 architecture specific changes to prevent the possible race conditions. Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: fix namespace problem and sparc64 buildRusty Lynch2005-07-05
| | | | | | | | | | | | The following renames arch_init, a kprobes function for performing any architecture specific initialization, to arch_init_kprobes in order to cleanup the namespace. Also, this patch adds arch_init_kprobes to sparc64 to fix the sparc64 kprobes build from the last return probe patch. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Return probe redesign: i386 specific changesRusty Lynch2005-06-27
| | | | | | | | | | | | | | | | The following patch contains the i386 specific changes for the new return probe design. Changes include: * Removing the architecture specific functions for querying a return probe instance off a stack address * Complete rework onf arch_prepare_kretprobe() and trampoline_probe_handler() * Removing trampoline_post_handler() * Adding arch_init() so that now we handle registering the return probe trampoline instead of kernel/kprobes.c doing it Signed-off-by: Rusty Lynch <rusty.lynch@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: Temporary disarming of reentrant probe for i386Prasanna S Panchamukhi2005-06-23
| | | | | | | | | | This patch includes i386 architecture specific changes to support temporary disarming on reentrancy of probes. Signed-of-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: moves lock-unlock to non-arch kprobe_flush_taskHien Nguyen2005-06-23
| | | | | | | | | | This patch moves the lock/unlock of the arch specific kprobe_flush_task() to the non-arch specific kprobe_flusk_task(). Signed-off-by: Hien Nguyen <hien@us.ibm.com> Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Move kprobe [dis]arming into arch specific codeRusty Lynch2005-06-23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The architecture independent code of the current kprobes implementation is arming and disarming kprobes at registration time. The problem is that the code is assuming that arming and disarming is a just done by a simple write of some magic value to an address. This is problematic for ia64 where our instructions look more like structures, and we can not insert break points by just doing something like: *p->addr = BREAKPOINT_INSTRUCTION; The following patch to 2.6.12-rc4-mm2 adds two new architecture dependent functions: * void arch_arm_kprobe(struct kprobe *p) * void arch_disarm_kprobe(struct kprobe *p) and then adds the new functions for each of the architectures that already implement kprobes (spar64/ppc64/i386/x86_64). I thought arch_[dis]arm_kprobe was the most descriptive of what was really happening, but each of the architectures already had a disarm_kprobe() function that was really a "disarm and do some other clean-up items as needed when you stumble across a recursive kprobe." So... I took the liberty of changing the code that was calling disarm_kprobe() to call arch_disarm_kprobe(), and then do the cleanup in the block of code dealing with the recursive kprobe case. So far this patch as been tested on i386, x86_64, and ppc64, but still needs to be tested in sparc64. Signed-off-by: Rusty Lynch <rusty.lynch@intel.com> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kprobes: function-return probesHien Nguyen2005-06-23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds function-return probes to kprobes for the i386 architecture. This enables you to establish a handler to be run when a function returns. 1. API Two new functions are added to kprobes: int register_kretprobe(struct kretprobe *rp); void unregister_kretprobe(struct kretprobe *rp); 2. Registration and unregistration 2.1 Register To register a function-return probe, the user populates the following fields in a kretprobe object and calls register_kretprobe() with the kretprobe address as an argument: kp.addr - the function's address handler - this function is run after the ret instruction executes, but before control returns to the return address in the caller. maxactive - The maximum number of instances of the probed function that can be active concurrently. For example, if the function is non- recursive and is called with a spinlock or mutex held, maxactive = 1 should be enough. If the function is non-recursive and can never relinquish the CPU (e.g., via a semaphore or preemption), NR_CPUS should be enough. maxactive is used to determine how many kretprobe_instance objects to allocate for this particular probed function. If maxactive <= 0, it is set to a default value (if CONFIG_PREEMPT maxactive=max(10, 2 * NR_CPUS) else maxactive=NR_CPUS) For example: struct kretprobe rp; rp.kp.addr = /* entrypoint address */ rp.handler = /*return probe handler */ rp.maxactive = /* e.g., 1 or NR_CPUS or 0, see the above explanation */ register_kretprobe(&rp); The following field may also be of interest: nmissed - Initialized to zero when the function-return probe is registered, and incremented every time the probed function is entered but there is no kretprobe_instance object available for establishing the function-return probe (i.e., because maxactive was set too low). 2.2 Unregister To unregiter a function-return probe, the user calls unregister_kretprobe() with the same kretprobe object as registered previously. If a probed function is running when the return probe is unregistered, the function will return as expected, but the handler won't be run. 3. Limitations 3.1 This patch supports only the i386 architecture, but patches for x86_64 and ppc64 are anticipated soon. 3.2 Return probes operates by replacing the return address in the stack (or in a known register, such as the lr register for ppc). This may cause __builtin_return_address(0), when invoked from the return-probed function, to return the address of the return-probes trampoline. 3.3 This implementation uses the "Multiprobes at an address" feature in 2.6.12-rc3-mm3. 3.4 Due to a limitation in multi-probes, you cannot currently establish a return probe and a jprobe on the same function. A patch to remove this limitation is being tested. This feature is required by SystemTap (http://sourceware.org/systemtap), and reflects ideas contributed by several SystemTap developers, including Will Cohen and Ananth Mavinakayanahalli. Signed-off-by: Hien Nguyen <hien@us.ibm.com> Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Frederik Deweerdt <frederik.deweerdt@laposte.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Kprobes: Incorrect handling of probes on ret/lret instructionPrasanna S Panchamukhi2005-05-05
| | | | | | | | | | | | | Kprobes could not handle the insertion of a probe on the ret/lret instruction and used to oops after single stepping since kprobes was modifying eip/rip incorrectly. Adjustment of eip/rip is not required after single stepping in case of ret/lret instruction, because eip/rip points to the correct location after execution of the ret/lret instruction. This patch fixes the above problem. Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds2005-04-16
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!