From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933207Ab1EXSjg (ORCPT ); Tue, 24 May 2011 14:39:36 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:60946 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933003Ab1EXSiS (ORCPT ); Tue, 24 May 2011 14:38:18 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references; b=skgfp1ykitVsVYkcPMUXUej8zBM7UFUvwf1fyieGMBeHEMnTjUijfpIQITaLChfPn2 6y/ncrUWDSZlDL8ckCCTEz0q2+iunKFGm3ttMZFAoaDj7/2d1c6239OBxEHBti8YDCro zjzgkMjmjoILVJg99SqsjhCU/zgJFFZXpArlo= From: Tejun Heo To: oleg@redhat.com Cc: vda.linux@googlemail.com, jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu, bdonlan@gmail.com, pedro@codesourcery.com, Tejun Heo Subject: [PATCH 16/19] ptrace: make group stop state visible via PTRACE_GETSIGINFO Date: Tue, 24 May 2011 20:37:36 +0200 Message-Id: <1306262259-7285-17-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1306262259-7285-1-git-send-email-tj@kernel.org> References: <1306262259-7285-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If tracee is SEIZED, PTRACE_EVENT_STOP trap is used for group stop; however, there currently is no way to find out which signal initiated the group stop or if the group stop is still in effect. This patch changes PTRACE_GET_SIGINFO on ptrace traps to report group stop information via si.si_signo and si.si_pt_flags. Note that it's only available if tracee was seized. This doesn't address notification and tracer has to put tracee in an appropriate trap and poll the flag. Later patches will deal with notification and trap transition. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts1s = { .tv_sec = 1 }; int main(int argc, char **argv) { pid_t tracee, tracer; int i; tracee = fork(); if (!tracee) while (1) nanosleep(&ts1s, NULL); tracer = fork(); if (!tracer) { int last_stopped = 0, stopped; siginfo_t si; ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); repeat: ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_GETSIGINFO, tracee, NULL, &si); if (si.si_code) { stopped = !!si.si_status; if (stopped != last_stopped) printf("tracer: stopped=%d signo=%d\n", stopped, si.si_signo); last_stopped = stopped; ptrace(PTRACE_CONT, tracee, NULL, NULL); } else { printf("tracer: SIG %d\n", si.si_signo); ptrace(PTRACE_CONT, tracee, NULL, (void *)(unsigned long)si.si_signo); } goto repeat; } for (i = 0; i < 3; i++) { nanosleep(&ts1s, NULL); printf("mother: SIGSTOP\n"); kill(tracee, SIGSTOP); nanosleep(&ts1s, NULL); printf("mother: SIGCONT\n"); kill(tracee, SIGCONT); } nanosleep(&ts1s, NULL); kill(tracer, SIGKILL); kill(tracee, SIGKILL); return 0; } Tracer delivers signal, resumes group stop, induces INTERRUPT traps and reports group stop state change in busy loop. Mother sends SIGSTOP or CONT to tracee on each second. Note that si_pt_flags and flag testing are replaced with si_status testing. si_status occupies the same offset as si_pt_flags and PTRACE_SI_STOPPED is the only flag defined, so I took a dirty short cut. # ./test-stopped mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: stopped=0 signo=5 tracer: SIG 18 mother: SIGSTOP tracer: SIG 19 tracer: stopped=1 signo=19 mother: SIGCONT tracer: SIG 18 tracer: stopped=0 signo=5 -v2: Local variable sig defined inside if() block it's used in as suggested by Oleg. Signed-off-by: Tejun Heo Cc: Oleg Nesterov --- include/linux/ptrace.h | 3 +++ kernel/ptrace.c | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+), 0 deletions(-) diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 8c45eb0..1e84960 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -73,6 +73,9 @@ #define PTRACE_EVENT_EXIT 6 #define PTRACE_EVENT_STOP 7 +/* flags in siginfo.si_pt_flags from PTRACE_GETSIGINFO */ +#define PTRACE_SI_STOPPED 0x00000001 /* tracee is job control stopped */ + #include #ifdef __KERNEL__ diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 851870c..a205c98 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -583,6 +583,25 @@ static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info) error = 0; *info = *child->last_siginfo; + + /* + * If reporting ptrace trap for a seized tracee, enable reporting + * of info->si_pt_flags. + */ + if ((child->ptrace & PT_SEIZED) && + (info->si_code & __SI_MASK) == __SI_TRAP) { + struct signal_struct *sig = child->signal; + + /* + * Report whether group stop is in effect w/ SI_STOPPED and + * if so which signal caused it. + */ + if (sig->group_stop_count || sig->flags & SIGNAL_STOP_STOPPED) { + info->si_pt_flags |= PTRACE_SI_STOPPED; + info->si_signo = child->jobctl & JOBCTL_STOP_SIGMASK; + WARN_ON_ONCE(!info->si_signo); + } + } out_unlock: unlock_task_sighand(child, &flags); return error; -- 1.7.1