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ptrace: add ability to retrieve signals without removing from a queue (v4)

This patch adds a new ptrace request PTRACE_PEEKSIGINFO. This request is used to retrieve information about pending signals starting with the specified sequence number. Siginfo_t structures are copied from the child into the buffer starting at "data". The argument "addr" is a pointer to struct ptrace_peeksiginfo_args. struct ptrace_peeksiginfo_args { u64 off; /* from which siginfo to start */ u32 flags; s32 nr; /* how may siginfos to take */ }; "nr" has type "s32", because ptrace() returns "long", which has 32 bits on i386 and a negative values is used for errors. Currently here is only one flag PTRACE_PEEKSIGINFO_SHARED for dumping signals from process-wide queue. If this flag is not set, signals are read from a per-thread queue. The request PTRACE_PEEKSIGINFO returns a number of dumped signals. If a signal with the specified sequence number doesn't exist, ptrace returns zero. The request returns an error, if no signal has been dumped. Errors: EINVAL - one or more specified flags are not supported or nr is negative EFAULT - buf or addr is outside your accessible address space. A result siginfo contains a kernel part of si_code which usually striped, but it's required for queuing the same siginfo back during restore of pending signals. This functionality is required for checkpointing pending signals. Pedro Alves suggested using it in "gdb" to peek at pending signals. gdb already uses PTRACE_GETSIGINFO to get the siginfo for the signal which was already dequeued. This functionality allows gdb to look at the pending signals which were not reported yet. The prototype of this code was developed by Oleg Nesterov.

Andrey Vagin committed 13 years ago

Commit 84c751b1 parent 865f38a2 files · +92 −0Browse files

Unified · Split

2 files
  1. include/uapi/linux/ptrace.h +12 −0
  2. kernel/ptrace.c +80 −0
include/uapi/linux/ptrace.h+12−0
@@ -5,6 +5,7 @@ · 4 unmodified lines
5 5
6/* has the defines to get at the registers. */6/* has the defines to get at the registers. */
7 7
8#include <linux/types.h>
8 9
9#define PTRACE_TRACEME 010#define PTRACE_TRACEME 0
10#define PTRACE_PEEKTEXT 111#define PTRACE_PEEKTEXT 1
@@ -52,6 +53,17 @@ · 41 unmodified lines
52#define PTRACE_INTERRUPT 0x420753#define PTRACE_INTERRUPT 0x4207
53#define PTRACE_LISTEN 0x420854#define PTRACE_LISTEN 0x4208
54 55
56#define PTRACE_PEEKSIGINFO 0x4209
57
58struct ptrace_peeksiginfo_args {
59 __u64 off; /* from which siginfo to start */
60 __u32 flags;
61 __s32 nr; /* how may siginfos to take */
62};
63
64/* Read signals from a shared (process wide) queue */
65#define PTRACE_PEEKSIGINFO_SHARED (1 << 0)
66
55/* Wait extended result codes for the above trace options. */67/* Wait extended result codes for the above trace options. */
56#define PTRACE_EVENT_FORK 168#define PTRACE_EVENT_FORK 1
57#define PTRACE_EVENT_VFORK 269#define PTRACE_EVENT_VFORK 2
kernel/ptrace.c+80−0
@@ -24,6 +24,7 @@ · 23 unmodified lines
24#include <linux/regset.h>24#include <linux/regset.h>
25#include <linux/hw_breakpoint.h>25#include <linux/hw_breakpoint.h>
26#include <linux/cn_proc.h>26#include <linux/cn_proc.h>
27#include <linux/compat.h>
27 28
28 29
29static int ptrace_trapping_sleep_fn(void *flags)30static int ptrace_trapping_sleep_fn(void *flags)
@@ -618,6 +619,81 @@ static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info) · 588 unmodified lines
618 return error;619 return error;
619}620}
620 621
622static int ptrace_peek_siginfo(struct task_struct *child,
623 unsigned long addr,
624 unsigned long data)
625{
626 struct ptrace_peeksiginfo_args arg;
627 struct sigpending *pending;
628 struct sigqueue *q;
629 int ret, i;
630
631 ret = copy_from_user(&arg, (void __user *) addr,
632 sizeof(struct ptrace_peeksiginfo_args));
633 if (ret)
634 return -EFAULT;
635
636 if (arg.flags & ~PTRACE_PEEKSIGINFO_SHARED)
637 return -EINVAL; /* unknown flags */
638
639 if (arg.nr < 0)
640 return -EINVAL;
641
642 if (arg.flags & PTRACE_PEEKSIGINFO_SHARED)
643 pending = &child->signal->shared_pending;
644 else
645 pending = &child->pending;
646
647 for (i = 0; i < arg.nr; ) {
648 siginfo_t info;
649 s32 off = arg.off + i;
650
651 spin_lock_irq(&child->sighand->siglock);
652 list_for_each_entry(q, &pending->list, list) {
653 if (!off--) {
654 copy_siginfo(&info, &q->info);
655 break;
656 }
657 }
658 spin_unlock_irq(&child->sighand->siglock);
659
660 if (off >= 0) /* beyond the end of the list */
661 break;
662
663#ifdef CONFIG_COMPAT
664 if (unlikely(is_compat_task())) {
665 compat_siginfo_t __user *uinfo = compat_ptr(data);
666
667 ret = copy_siginfo_to_user32(uinfo, &info);
668 ret |= __put_user(info.si_code, &uinfo->si_code);
669 } else
670#endif
671 {
672 siginfo_t __user *uinfo = (siginfo_t __user *) data;
673
674 ret = copy_siginfo_to_user(uinfo, &info);
675 ret |= __put_user(info.si_code, &uinfo->si_code);
676 }
677
678 if (ret) {
679 ret = -EFAULT;
680 break;
681 }
682
683 data += sizeof(siginfo_t);
684 i++;
685
686 if (signal_pending(current))
687 break;
688
689 cond_resched();
690 }
691
692 if (i > 0)
693 return i;
694
695 return ret;
696}
621 697
622#ifdef PTRACE_SINGLESTEP698#ifdef PTRACE_SINGLESTEP
623#define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)699#define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
@@ -748,6 +824,10 @@ int ptrace_request(struct task_struct *child, long request, · 124 unmodified lines
748 ret = put_user(child->ptrace_message, datalp);824 ret = put_user(child->ptrace_message, datalp);
749 break;825 break;
750 826
827 case PTRACE_PEEKSIGINFO:
828 ret = ptrace_peek_siginfo(child, addr, data);
829 break;
830
751 case PTRACE_GETSIGINFO:831 case PTRACE_GETSIGINFO:
752 ret = ptrace_getsiginfo(child, &siginfo);832 ret = ptrace_getsiginfo(child, &siginfo);
753 if (!ret)833 if (!ret)