aboutsummaryrefslogtreecommitdiffstats
path: root/lib
diff options
context:
space:
mode:
authorRoland McGrath <roland@redhat.com>2008-07-25 22:45:59 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-26 15:00:10 -0400
commitbbc698636ed48b6fcd323964e0f847a6a796325d (patch)
treec90d31c179aad154089a88d4845f1721ded40860 /lib
parent85ba2d862e521375a8ee01526c5c46b1f24bb4af (diff)
task_current_syscall
This adds the new function task_current_syscall() on machines where the asm/syscall.h interface is supported (CONFIG_HAVE_ARCH_TRACEHOOK). It's exported for modules to use in the future. This function safely samples the state of a blocked thread to collect what system call it is blocked in, and the six system call argument registers. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Reviewed-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile2
-rw-r--r--lib/syscall.c75
2 files changed, 77 insertions, 0 deletions
diff --git a/lib/Makefile b/lib/Makefile
index 9085ad6fa53d..942c7250f603 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -78,6 +78,8 @@ lib-$(CONFIG_GENERIC_BUG) += bug.o
78 78
79obj-$(CONFIG_HAVE_LMB) += lmb.o 79obj-$(CONFIG_HAVE_LMB) += lmb.o
80 80
81obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
82
81hostprogs-y := gen_crc32table 83hostprogs-y := gen_crc32table
82clean-files := crc32table.h 84clean-files := crc32table.h
83 85
diff --git a/lib/syscall.c b/lib/syscall.c
new file mode 100644
index 000000000000..a4f7067f72fa
--- /dev/null
+++ b/lib/syscall.c
@@ -0,0 +1,75 @@
1#include <linux/ptrace.h>
2#include <linux/sched.h>
3#include <linux/module.h>
4#include <asm/syscall.h>
5
6static int collect_syscall(struct task_struct *target, long *callno,
7 unsigned long args[6], unsigned int maxargs,
8 unsigned long *sp, unsigned long *pc)
9{
10 struct pt_regs *regs = task_pt_regs(target);
11 if (unlikely(!regs))
12 return -EAGAIN;
13
14 *sp = user_stack_pointer(regs);
15 *pc = instruction_pointer(regs);
16
17 *callno = syscall_get_nr(target, regs);
18 if (*callno != -1L && maxargs > 0)
19 syscall_get_arguments(target, regs, 0, maxargs, args);
20
21 return 0;
22}
23
24/**
25 * task_current_syscall - Discover what a blocked task is doing.
26 * @target: thread to examine
27 * @callno: filled with system call number or -1
28 * @args: filled with @maxargs system call arguments
29 * @maxargs: number of elements in @args to fill
30 * @sp: filled with user stack pointer
31 * @pc: filled with user PC
32 *
33 * If @target is blocked in a system call, returns zero with *@callno
34 * set to the the call's number and @args filled in with its arguments.
35 * Registers not used for system call arguments may not be available and
36 * it is not kosher to use &struct user_regset calls while the system
37 * call is still in progress. Note we may get this result if @target
38 * has finished its system call but not yet returned to user mode, such
39 * as when it's stopped for signal handling or syscall exit tracing.
40 *
41 * If @target is blocked in the kernel during a fault or exception,
42 * returns zero with *@callno set to -1 and does not fill in @args.
43 * If so, it's now safe to examine @target using &struct user_regset
44 * get() calls as long as we're sure @target won't return to user mode.
45 *
46 * Returns -%EAGAIN if @target does not remain blocked.
47 *
48 * Returns -%EINVAL if @maxargs is too large (maximum is six).
49 */
50int task_current_syscall(struct task_struct *target, long *callno,
51 unsigned long args[6], unsigned int maxargs,
52 unsigned long *sp, unsigned long *pc)
53{
54 long state;
55 unsigned long ncsw;
56
57 if (unlikely(maxargs > 6))
58 return -EINVAL;
59
60 if (target == current)
61 return collect_syscall(target, callno, args, maxargs, sp, pc);
62
63 state = target->state;
64 if (unlikely(!state))
65 return -EAGAIN;
66
67 ncsw = wait_task_inactive(target, state);
68 if (unlikely(!ncsw) ||
69 unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
70 unlikely(wait_task_inactive(target, state) != ncsw))
71 return -EAGAIN;
72
73 return 0;
74}
75EXPORT_SYMBOL_GPL(task_current_syscall);