[PATCH] Kprobes: prevent possible race conditions generic

There are possible race conditions if probes are placed on routines within the
kprobes files and routines used by the kprobes.  For example if you put probe
on get_kprobe() routines, the system can hang while inserting probes on any
routine such as do_fork().  Because while inserting probes on do_fork(),
register_kprobes() routine grabs the kprobes spin lock and executes
get_kprobe() routine and to handle probe of get_kprobe(), kprobes_handler()
gets executed and tries to grab kprobes spin lock, and spins forever.  This
patch avoids such possible race conditions by preventing probes on routines
within the kprobes file and routines used by kprobes.

I have modified the patches as per Andi Kleen's suggestion to move kprobes
routines and other routines used by kprobes to a seperate section
.kprobes.text.

Also moved page fault and exception handlers, general protection fault to
.kprobes.text section.

These patches have been tested on i386, x86_64 and ppc64 architectures, also
compiled on ia64 and sparc64 architectures.

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>

4 files changed, 17 insertions, 0 deletions

diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 450eae22c39a..886dbd116899 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -12,5 +12,6 @@ extern char _sextratext[] __attribute__((weak));
 extern char _eextratext[] __attribute__((weak));
 extern char _end[];
 extern char __per_cpu_start[], __per_cpu_end[];
+extern char __kprobes_text_start[], __kprobes_text_end[];
 
 #endif /* _ASM_GENERIC_SECTIONS_H_ */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3fa94288aa93..6f857be2b644 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -97,3 +97,9 @@
                 VMLINUX_SYMBOL(__lock_text_start) = .;                  \
                 *(.spinlock.text)                                       \
                 VMLINUX_SYMBOL(__lock_text_end) = .;
+
+#define KPROBES_TEXT                                                    \
+                ALIGN_FUNCTION();                                       \
+                VMLINUX_SYMBOL(__kprobes_text_start) = .;               \
+                *(.kprobes.text)                                        \
+                VMLINUX_SYMBOL(__kprobes_text_end) = .;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e050fc2d4c26..e30afdca7917 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -42,6 +42,9 @@
 #define KPROBE_REENTER          0x00000004
 #define KPROBE_HIT_SSDONE       0x00000008
 
+/* Attach to insert probes on any functions which should be ignored*/
+#define __kprobes       __attribute__((__section__(".kprobes.text")))
+
 struct kprobe;
 struct pt_regs;
 struct kretprobe;
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index 338f7795d8a0..147eb01e0d4b 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -33,6 +33,13 @@
   ALIGN; \
   name:
 
+#define KPROBE_ENTRY(name) \
+  .section .kprobes.text, "ax"; \
+  .globl name; \
+  ALIGN; \
+  name:
+
+
 #endif
 
 #define NORET_TYPE    /**/