Date: Tue, 22 Jun 2021 01:46:09 GMT From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 4f88de7e09e7 - stable/13 - Add a knob to not drop signal with default ignored or ignored actions Message-ID: <202106220146.15M1k9v8066000@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch stable/13 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=4f88de7e09e7a1370aebd0a7ef64b3e8134c0cd3 commit 4f88de7e09e7a1370aebd0a7ef64b3e8134c0cd3 Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2021-06-05 12:42:27 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2021-06-22 01:45:31 +0000 Add a knob to not drop signal with default ignored or ignored actions (cherry picked from commit bc38762474caed2d41d2562e28f56aa211f47ceb) --- sys/kern/kern_sig.c | 65 +++++++++++++++++++++++++++++++---------------------- sys/sys/proc.h | 1 + sys/sys/sysent.h | 1 + 3 files changed, 40 insertions(+), 27 deletions(-) diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c index 1cab25aa5a40..4f6f424fb05d 100644 --- a/sys/kern/kern_sig.c +++ b/sys/kern/kern_sig.c @@ -163,6 +163,12 @@ SYSCTL_BOOL(_kern, OID_AUTO, sigfastblock_fetch_always, CTLFLAG_RWTUN, "Fetch sigfastblock word on each syscall entry for proper " "blocking semantic"); +static bool kern_sig_discard_ign = true; +SYSCTL_BOOL(_kern, OID_AUTO, sig_discard_ign, CTLFLAG_RWTUN, + &kern_sig_discard_ign, 0, + "Discard ignored signals on delivery, otherwise queue them to " + "the target queue"); + SYSINIT(signal, SI_SUB_P1003_1B, SI_ORDER_FIRST+3, sigqueue_start, NULL); /* @@ -1290,6 +1296,9 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi, PROC_LOCK(p); saved_mask = td->td_sigmask; SIGSETNAND(td->td_sigmask, waitset); + if ((p->p_sysent->sv_flags & SV_SIG_DISCIGN) != 0 || + !kern_sig_discard_ign) + td->td_pflags2 |= TDP2_SIGWAIT; for (;;) { mtx_lock(&ps->ps_mtx); sig = cursig(td); @@ -1352,6 +1361,7 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi, if (error == 0 && (p->p_ptevents & PTRACE_SYSCALL) != 0) traced = true; } + td->td_pflags2 &= ~TDP2_SIGWAIT; new_block = saved_mask; SIGSETNAND(new_block, td->td_sigmask); @@ -2200,22 +2210,25 @@ tdsendsignal(struct proc *p, struct thread *td, int sig, ksiginfo_t *ksi) SDT_PROBE3(proc, , , signal__send, td, p, sig); /* - * If the signal is being ignored, - * then we forget about it immediately. - * (Note: we don't set SIGCONT in ps_sigignore, - * and if it is set to SIG_IGN, - * action will be SIG_DFL here.) + * If the signal is being ignored, then we forget about it + * immediately, except when the target process executes + * sigwait(). (Note: we don't set SIGCONT in ps_sigignore, + * and if it is set to SIG_IGN, action will be SIG_DFL here.) */ mtx_lock(&ps->ps_mtx); if (SIGISMEMBER(ps->ps_sigignore, sig)) { - SDT_PROBE3(proc, , , signal__discard, td, p, sig); + if (kern_sig_discard_ign && + (p->p_sysent->sv_flags & SV_SIG_DISCIGN) == 0) { + SDT_PROBE3(proc, , , signal__discard, td, p, sig); - mtx_unlock(&ps->ps_mtx); - if (ksi && (ksi->ksi_flags & KSI_INS)) - ksiginfo_tryfree(ksi); - return (ret); - } - if (SIGISMEMBER(td->td_sigmask, sig)) + mtx_unlock(&ps->ps_mtx); + if (ksi && (ksi->ksi_flags & KSI_INS)) + ksiginfo_tryfree(ksi); + return (ret); + } else { + action = SIG_CATCH; + } + } else if (SIGISMEMBER(td->td_sigmask, sig)) action = SIG_HOLD; else if (SIGISMEMBER(ps->ps_sigcatch, sig)) action = SIG_CATCH; @@ -2950,11 +2963,13 @@ issignal(struct thread *td) } /* - * We should see pending but ignored signals - * only if P_TRACED was on when they were posted. + * We should allow pending but ignored signals below + * only if there is sigwait() active, or P_TRACED was + * on when they were posted. */ if (SIGISMEMBER(ps->ps_sigignore, sig) && - (p->p_flag & P_TRACED) == 0) { + (p->p_flag & P_TRACED) == 0 && + (td->td_pflags2 & TDP2_SIGWAIT) == 0) { sigqueue_delete(&td->td_sigqueue, sig); sigqueue_delete(&p->p_sigqueue, sig); continue; @@ -3066,10 +3081,11 @@ issignal(struct thread *td) PROC_SUNLOCK(p); mtx_lock(&ps->ps_mtx); goto next; - } else if (prop & SIGPROP_IGNORE) { + } else if ((prop & SIGPROP_IGNORE) != 0 && + (td->td_pflags2 & TDP2_SIGWAIT) == 0) { /* - * Except for SIGCONT, shouldn't get here. - * Default action is to ignore; drop it. + * Default action is to ignore; drop it if + * not in kern_sigtimedwait(). */ break; /* == ignore */ } else @@ -3077,15 +3093,10 @@ issignal(struct thread *td) /*NOTREACHED*/ case (intptr_t)SIG_IGN: - /* - * Masking above should prevent us ever trying - * to take action on an ignored signal other - * than SIGCONT, unless process is traced. - */ - if ((prop & SIGPROP_CONT) == 0 && - (p->p_flag & P_TRACED) == 0) - printf("issignal\n"); - break; /* == ignore */ + if ((td->td_pflags2 & TDP2_SIGWAIT) == 0) + break; /* == ignore */ + else + return (sig); default: /* diff --git a/sys/sys/proc.h b/sys/sys/proc.h index d4476ac8d410..373e62bd266d 100644 --- a/sys/sys/proc.h +++ b/sys/sys/proc.h @@ -529,6 +529,7 @@ do { \ #define TDP2_SBPAGES 0x00000001 /* Owns sbusy on some pages */ #define TDP2_COMPAT32RB 0x00000002 /* compat32 ABI for robust lists */ #define TDP2_ACCT 0x00000004 /* Doing accounting */ +#define TDP2_SIGWAIT 0x00000008 /* Ignore ignored signals */ /* * Reasons that the current thread can not be run yet. diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h index c2cbd77a92b9..95e9dcb1a335 100644 --- a/sys/sys/sysent.h +++ b/sys/sys/sysent.h @@ -161,6 +161,7 @@ struct sysentvec { #define SV_TIMEKEEP 0x040000 /* Shared page timehands. */ #define SV_ASLR 0x080000 /* ASLR allowed. */ #define SV_RNG_SEED_VER 0x100000 /* random(4) reseed generation. */ +#define SV_SIG_DISCIGN 0x200000 /* Do not discard ignored signals */ #define SV_ABI_MASK 0xff #define SV_PROC_FLAG(p, x) ((p)->p_sysent->sv_flags & (x))
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202106220146.15M1k9v8066000>