Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 18/19] ptrace: add JOBCTL_BLOCK_NOTIFY | Date | Tue, 24 May 2011 20:37:38 +0200 |
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For to-be-added notification retraps, other tasks need to be able to tell whether ptrace request is currently in progress while tracee is in STOP trap. This patch adds JOBCTL_BLOCK_NOTIFY which is set on ptrace_check_attach() if the request requires tracee to be trapped and it's trapped for STOP, and cleared when ptrace syscall finishes.
This flag isn't used yet.
-v2: ptrace_put_task_struct() reorganized per Oleg's comment.
Signed-off-by: Tejun Heo <tj@kernel.org> --- include/linux/ptrace.h | 2 + include/linux/sched.h | 1 + kernel/ptrace.c | 54 ++++++++++++++++++++++++++++++++++++++++++----- 3 files changed, 51 insertions(+), 6 deletions(-)
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 1e84960..2e39f81 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -73,6 +73,8 @@ #define PTRACE_EVENT_EXIT 6 #define PTRACE_EVENT_STOP 7 +#define PTRACE_STOP_SI_CODE (__SI_TRAP | SIGTRAP | PTRACE_EVENT_STOP << 8) + /* flags in siginfo.si_pt_flags from PTRACE_GETSIGINFO */ #define PTRACE_SI_STOPPED 0x00000001 /* tracee is job control stopped */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 9a0e1bc..9298f97 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1801,6 +1801,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t * #define JOBCTL_STOP_CONSUME (1 << 18) /* consume group stop count */ #define JOBCTL_TRAP_STOP (1 << 19) /* trap for STOP */ #define JOBCTL_TRAPPING (1 << 21) /* switching to TRACED */ +#define JOBCTL_BLOCK_NOTIFY (1 << 22) /* block NOTIFY re-traps */ #define JOBCTL_TRAP_MASK JOBCTL_TRAP_STOP #define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index a9b3c67..1982d7a 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -128,11 +128,13 @@ void __ptrace_unlink(struct task_struct *child) spin_lock(&child->sighand->siglock); /* - * Clear all pending traps and TRAPPING. TRAPPING should be - * cleared regardless of JOBCTL_STOP_PENDING. Do it explicitly. + * Clear all pending traps, TRAPPING and BLOCK_NOTIFY. TRAPPING + * should be cleared regardless of JOBCTL_STOP_PENDING. Do it + * explicitly. */ task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK); task_clear_jobctl_trapping(child); + child->jobctl &= ~JOBCTL_BLOCK_NOTIFY; /* * Reinstate JOBCTL_STOP_PENDING if group stop is in effect and @@ -191,10 +193,24 @@ int ptrace_check_attach(struct task_struct *child, bool ignore_state) */ spin_lock_irq(&child->sighand->siglock); WARN_ON_ONCE(task_is_stopped(child)); - if (task_is_traced(child) || ignore_state) + + if (ignore_state) { + ret = 0; + } else if (task_is_traced(child)) { + siginfo_t *si = child->last_siginfo; + + /* + * If STOP trapped, ptrace notification may cause + * re-traps, which we don't want while ptrace + * request is in progress. Block notification. + */ + if (si && si->si_code == PTRACE_STOP_SI_CODE) + child->jobctl |= JOBCTL_BLOCK_NOTIFY; ret = 0; - else if (ptrace_wait_trapping(child)) + } else if (ptrace_wait_trapping(child)) { return restart_syscall(); + } + spin_unlock_irq(&child->sighand->siglock); } read_unlock(&tasklist_lock); @@ -887,6 +903,32 @@ static struct task_struct *ptrace_get_task_struct(pid_t pid) #define arch_ptrace_attach(child) do { } while (0) #endif +/** + * ptrace_put_task_struct - ptrace request processing done, put child + * @child: child task struct to put + * + * ptrace request processing for @child is finished. Clean up and put + * @child. This function clears %JOBCTL_BLOCK_NOTIFY which can be set by + * ptrace_check_attach(). @child might not be being ptraced by %current. + */ +static void ptrace_put_task_struct(struct task_struct *child) +{ + unsigned long flags; + + if (!(child->jobctl & JOBCTL_BLOCK_NOTIFY)) + goto out_put; + + if (unlikely(!(child->ptrace & PT_PTRACED) || child->parent != current)) + goto out_put; + + if (likely(lock_task_sighand(child, &flags))) { + child->jobctl &= ~JOBCTL_BLOCK_NOTIFY; + unlock_task_sighand(child, &flags); + } +out_put: + put_task_struct(child); +} + SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, unsigned long, data) { @@ -925,7 +967,7 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, ret = arch_ptrace(child, request, addr, data); out_put_task_struct: - put_task_struct(child); + ptrace_put_task_struct(child); out: return ret; } @@ -1066,7 +1108,7 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, ret = compat_arch_ptrace(child, request, addr, data); out_put_task_struct: - put_task_struct(child); + ptrace_put_task_struct(child); out: return ret; } -- 1.7.1
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