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[192.0.145.146]) by smtp.gmail.com with ESMTPSA id m7-20020a924a07000000b0030d8ee6090fsm4483466ilf.35.2023.01.11.13.44.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Jan 2023 13:44:22 -0800 (PST) Message-ID: <12e296b4-c72d-1198-f7fc-fac70614b46d@redhat.com> Date: Wed, 11 Jan 2023 16:44:21 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2 04/11] linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn To: Adhemerval Zanella , libc-alpha@sourceware.org, Szabolcs Nagy , "H . J . Lu" Cc: Christian Brauner References: <20221104190112.2566409-1-adhemerval.zanella@linaro.org> <20221104190112.2566409-5-adhemerval.zanella@linaro.org> Organization: Red Hat In-Reply-To: <20221104190112.2566409-5-adhemerval.zanella@linaro.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Carlos O'Donell via Libc-alpha Reply-To: Carlos O'Donell Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On 11/4/22 15:01, Adhemerval Zanella via Libc-alpha wrote: > The clone3 flag resets all signal handlers of the child not set to > SIG_IGN to SIG_DFL. It allows to skip most of the sigaction calls > to setup child signal handling, where previously a posix_spawn > has to issue 2 times NSIG sigaction calls (one to obtain the current > disposition and another to set either SIG_DFL or SIG_IGN). > > The expection is POSIX_SPAWN_SETSIGDEF the child still setup the > signal for the case the disposition is SIG_IGN. > > It also need to handle the fallback where clone3 is not available, > to set the fallback in child. This is done by splitting of > __clone_internal_fallback from __clone_internal. > See original v2 review. Please post v4. > Checked on x86_64-linux-gnu. > --- > include/clone_internal.h | 5 + > posix/Makefile | 3 +- > posix/tst-spawn7.c | 179 +++++++++++++++++++++++ > sysdeps/unix/sysv/linux/Makefile | 3 +- > sysdeps/unix/sysv/linux/clone-internal.c | 37 +++-- > sysdeps/unix/sysv/linux/clone3.h | 7 + > sysdeps/unix/sysv/linux/spawni.c | 31 ++-- > 7 files changed, 238 insertions(+), 27 deletions(-) > create mode 100644 posix/tst-spawn7.c > > diff --git a/include/clone_internal.h b/include/clone_internal.h > index 5a48c7caa5..81292b3eb1 100644 > --- a/include/clone_internal.h > +++ b/include/clone_internal.h > @@ -26,6 +26,11 @@ extern int __clone3 (struct clone_args *__cl_args, size_t __size, > fall back to clone or clone2. */ > extern int __clone_internal (struct clone_args *__cl_args, > int (*__func) (void *__arg), void *__arg); > +/* The fallback code which calls clone/clone2 based on clone3 arguments. */ > +extern int __clone_internal_fallback (struct clone_args *__cl_args, > + int (*__func) (void *__arg), > + void *__arg) > + attribute_hidden; > > #ifndef _ISOMAC > libc_hidden_proto (__clone3) > diff --git a/posix/Makefile b/posix/Makefile > index 4d60449426..6e61ce50f2 100644 > --- a/posix/Makefile > +++ b/posix/Makefile > @@ -109,7 +109,7 @@ tests := test-errno tstgetopt testfnm runtests runptests \ > tst-glob-tilde test-ssize-max tst-spawn4 bug-regex37 \ > bug-regex38 tst-regcomp-truncated tst-spawn-chdir \ > tst-wordexp-nocmd tst-execveat tst-spawn5 \ > - tst-sched_getaffinity tst-spawn6 > + tst-sched_getaffinity tst-spawn6 tst-spawn7 > > # Test for the glob symbol version that was replaced in glibc 2.27. > ifeq ($(have-GLIBC_2.26)$(build-shared),yesyes) > @@ -291,6 +291,7 @@ tst-spawn-ARGS = -- $(host-test-program-cmd) > tst-spawn-static-ARGS = $(tst-spawn-ARGS) > tst-spawn5-ARGS = -- $(host-test-program-cmd) > tst-spawn6-ARGS = -- $(host-test-program-cmd) > +tst-spawn7-ARGS = -- $(host-test-program-cmd) > tst-dir-ARGS = `pwd` `cd $(common-objdir)/$(subdir); pwd` `cd $(common-objdir); pwd` $(objpfx)tst-dir > tst-chmod-ARGS = $(objdir) > tst-vfork3-ARGS = --test-dir=$(objpfx) > diff --git a/posix/tst-spawn7.c b/posix/tst-spawn7.c > new file mode 100644 > index 0000000000..7cb7347c58 > --- /dev/null > +++ b/posix/tst-spawn7.c > @@ -0,0 +1,179 @@ > +/* Tests for posix_spawn signal handling. > + Copyright (C) 2022 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +/* Nonzero if the program gets called via `exec'. */ > +#define CMDLINE_OPTIONS \ > + { "restart", no_argument, &restart, 1 }, > +static int restart; > + > +/* Hold the four initial argument used to respawn the process, plus the extra > + '--direct', '--restart', the check type ('SIG_IGN' or 'SIG_DFL'), and a > + final NULL. */ > +static char *spargs[8]; > +static int check_type_argc; > + > +/* Called on process re-execution. */ > +_Noreturn static void > +handle_restart (int argc, char *argv[]) > +{ > + assert (argc == 1); > + > + if (strcmp (argv[0], "SIG_DFL") == 0) > + { > + for (int i = 1; i < NSIG; i++) > + { > + struct sigaction sa; > + int r = sigaction (i, NULL, &sa); > + /* Skip internal signals (such as SIGCANCEL). */ > + if (r == -1) > + continue; > + TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL); > + } > + exit (EXIT_SUCCESS); > + } > + else if (strcmp (argv[0], "SIG_IGN") == 0) > + { > + for (int i = 1; i < NSIG; i++) > + { > + struct sigaction sa; > + int r = sigaction (i, NULL, &sa); > + /* Skip internal signals (such as SIGCANCEL). */ > + if (r == -1) > + continue; > + if (i == SIGUSR1 || i == SIGUSR2) > + TEST_VERIFY_EXIT (sa.sa_handler == SIG_IGN); > + else > + TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL); > + } > + exit (EXIT_SUCCESS); > + } > + > + exit (EXIT_FAILURE); > +} > + > +static void > +spawn_signal_test (const char *type, const posix_spawnattr_t *attr) > +{ > + spargs[check_type_argc] = (char*) type; > + > + pid_t pid; > + int status; > + > + TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, attr, spargs, environ), 0); > + TEST_COMPARE (xwaitpid (pid, &status, 0), pid); > + TEST_VERIFY (WIFEXITED (status)); > + TEST_VERIFY (!WIFSIGNALED (status)); > + TEST_COMPARE (WEXITSTATUS (status), 0); > +} > + > +static void > +dummy_sa_handler (int) > +{ > +} > + > +static void > +do_test_signals (void) > +{ > + { > + /* Check if all signals handler are set to SIG_DFL on spawned process. */ > + spawn_signal_test ("SIG_DFL", NULL); > + } > + > + { > + /* Same as before, but set SIGUSR1 and SIGUSR2 to a handler different than > + SIG_IGN or SIG_DFL. */ > + struct sigaction sa = { 0 }; > + sa.sa_handler = dummy_sa_handler; > + xsigaction (SIGUSR1, &sa, NULL); > + xsigaction (SIGUSR2, &sa, NULL); > + spawn_signal_test ("SIG_DFL", NULL); > + } > + > + { > + /* Check if SIG_IGN is keep as is. */ > + struct sigaction sa = { 0 }; > + sa.sa_handler = SIG_IGN; > + xsigaction (SIGUSR1, &sa, NULL); > + xsigaction (SIGUSR2, &sa, NULL); > + spawn_signal_test ("SIG_IGN", NULL); > + } > + > + { > + /* Check if SIG_IGN handlers are set to SIG_DFL. */ > + posix_spawnattr_t attr; > + posix_spawnattr_init (&attr); > + sigset_t mask; > + sigemptyset (&mask); > + sigaddset (&mask, SIGUSR1); > + sigaddset (&mask, SIGUSR2); > + posix_spawnattr_setsigdefault (&attr, &mask); > + posix_spawnattr_setflags (&attr, POSIX_SPAWN_SETSIGDEF); > + spawn_signal_test ("SIG_DFL", &attr); > + posix_spawnattr_destroy (&attr); > + } > +} > + > +static int > +do_test (int argc, char *argv[]) > +{ > + /* We must have either: > + > + - one or four parameters if called initially: > + + argv[1]: path for ld.so optional > + + argv[2]: "--library-path" optional > + + argv[3]: the library path optional > + + argv[4]: the application name > + > + - six parameters left if called through re-execution: > + + argv[1]: the application name > + + argv[2]: check SIG_IGN/SIG_DFL. > + > + * When built with --enable-hardcoded-path-in-tests or issued without > + using the loader directly. */ > + > + if (restart) > + handle_restart (argc - 1, &argv[1]); > + > + TEST_VERIFY_EXIT (argc == 2 || argc == 5); > + > + int i; > + for (i = 0; i < argc - 1; i++) > + spargs[i] = argv[i + 1]; > + spargs[i++] = (char *) "--direct"; > + spargs[i++] = (char *) "--restart"; > + check_type_argc = i++; > + spargs[i] = NULL; > + > + > + do_test_signals (); > + > + return 0; > +} > + > +#define TEST_FUNCTION_ARGV do_test > +#include > diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile > index 60e4cb1521..c183ccd4ab 100644 > --- a/sysdeps/unix/sysv/linux/Makefile > +++ b/sysdeps/unix/sysv/linux/Makefile > @@ -175,8 +175,7 @@ tests-clone-internal = \ > tst-align-clone-internal \ > tst-clone2-internal \ > tst-clone3-internal \ > - tst-getpid1-internal \ > - tst-misalign-clone-internal > + tst-getpid1-internal > tests-internal += $(tests-clone-internal) > tests-static += $(tests-clone-internal) > > diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c > index a71effcbd3..7bc991e033 100644 > --- a/sysdeps/unix/sysv/linux/clone-internal.c > +++ b/sysdeps/unix/sysv/linux/clone-internal.c > @@ -44,27 +44,15 @@ _Static_assert (sizeof (struct clone_args) == CLONE_ARGS_SIZE_VER2, > "sizeof (struct clone_args) != CLONE_ARGS_SIZE_VER2"); > > int > -__clone_internal (struct clone_args *cl_args, > - int (*func) (void *arg), void *arg) > +__clone_internal_fallback (struct clone_args *cl_args, > + int (*func) (void *arg), void *arg) > { > - int ret; > -#ifdef HAVE_CLONE3_WRAPPER > - /* Try clone3 first. */ > - int saved_errno = errno; > - ret = __clone3 (cl_args, sizeof (*cl_args), func, arg); > - if (ret != -1 || errno != ENOSYS) > - return ret; > - > - /* NB: Restore errno since errno may be checked against non-zero > - return value. */ > - __set_errno (saved_errno); > -#endif > - > /* Map clone3 arguments to clone arguments. NB: No need to check > invalid clone3 specific bits in flags nor exit_signal since this > is an internal function. */ > int flags = cl_args->flags | cl_args->exit_signal; > void *stack = cast_to_pointer (cl_args->stack); > + int ret; > > #ifdef __ia64__ > ret = __clone2 (func, stack, cl_args->stack_size, > @@ -88,4 +76,23 @@ __clone_internal (struct clone_args *cl_args, > return ret; > } > > + > +int > +__clone_internal (struct clone_args *cl_args, > + int (*func) (void *arg), void *arg) > +{ > +#ifdef HAVE_CLONE3_WRAPPER > + int saved_errno = errno; > + int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg); > + if (ret != -1 || errno != ENOSYS) > + return ret; > + > + /* NB: Restore errno since errno may be checked against non-zero > + return value. */ > + __set_errno (saved_errno); > +#endif > + > + return __clone_internal_fallback (cl_args, func, arg); > +} > + > libc_hidden_def (__clone_internal) > diff --git a/sysdeps/unix/sysv/linux/clone3.h b/sysdeps/unix/sysv/linux/clone3.h > index 7c7e2cdcb0..7dd42ec2d2 100644 > --- a/sysdeps/unix/sysv/linux/clone3.h > +++ b/sysdeps/unix/sysv/linux/clone3.h > @@ -23,6 +23,13 @@ > #include > #include > > + > +/* Flags for the clone3 syscall. */ > +#define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and > + reset to SIG_DFL. */ > +#define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given > + the right permissions. */ > + > /* The unsigned 64-bit and 8-byte aligned integer type. */ > typedef __U64_TYPE __aligned_uint64_t __attribute__ ((__aligned__ (8))); > > diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c > index 65ee03c804..ebc3c3e521 100644 > --- a/sysdeps/unix/sysv/linux/spawni.c > +++ b/sysdeps/unix/sysv/linux/spawni.c > @@ -66,6 +66,7 @@ struct posix_spawn_args > ptrdiff_t argc; > char *const *envp; > int xflags; > + bool use_clone3; > int err; > }; > > @@ -104,12 +105,11 @@ __spawni_child (void *arguments) > const posix_spawnattr_t *restrict attr = args->attr; > const posix_spawn_file_actions_t *file_actions = args->fa; > > - /* The child must ensure that no signal handler are enabled because it shared > - memory with parent, so the signal disposition must be either SIG_DFL or > - SIG_IGN. It does by iterating over all signals and although it could > - possibly be more optimized (by tracking which signal potentially have a > - signal handler), it might requires system specific solutions (since the > - sigset_t data type can be very different on different architectures). */ > + /* The child must ensure that no signal handler is enabled because it > + shares memory with parent, so all signal dispositions must be either > + SIG_DFL or SIG_IGN. If clone3/CLONE_CLEAR_SIGHAND is used, there is > + only need to set the defined signals POSIX_SPAWN_SETSIGDEF to SIG_DFL; > + otherwise, the code iterates over all signals. */ > struct sigaction sa; > memset (&sa, '\0', sizeof (sa)); > > @@ -122,7 +122,7 @@ __spawni_child (void *arguments) > { > sa.sa_handler = SIG_DFL; > } > - else if (__sigismember (&hset, sig)) > + else if (!args->use_clone3 && __sigismember (&hset, sig)) > { > if (is_internal_signal (sig)) > sa.sa_handler = SIG_IGN; > @@ -382,12 +382,25 @@ __spawnix (pid_t * pid, const char *file, > for instance). */ > struct clone_args clone_args = > { > - .flags = CLONE_VM | CLONE_VFORK, > + /* Unsupported flags like CLONE_CLEAR_SIGHAND will be cleared up by > + __clone_internal_fallback. */ > + .flags = CLONE_CLEAR_SIGHAND | CLONE_VM | CLONE_VFORK, > .exit_signal = SIGCHLD, > .stack = (uintptr_t) stack, > .stack_size = stack_size, > }; > - new_pid = __clone_internal (&clone_args, __spawni_child, &args); > +#ifdef HAVE_CLONE3_WRAPPER > + args.use_clone3 = true; > + new_pid = __clone3 (&clone_args, sizeof (clone_args), __spawni_child, > + &args); > + /* clone3 was added on 5.3 and CLONE_CLEAR_SIGHAND on 5.5. */ > + if (new_pid == -1 && (errno == ENOSYS || errno == EINVAL)) > +#endif > + { > + args.use_clone3 = false; > + new_pid = __clone_internal_fallback (&clone_args, __spawni_child, > + &args); > + } > > /* It needs to collect the case where the auxiliary process was created > but failed to execute the file (due either any preparation step or -- Cheers, Carlos.