longjmp(3) t_sigstack: Use a sigaltstack per handler entry.
longjmp evidently doesn't reset the state of whether the process is executing on the alternate signal stack. So when we re-enter the signal handler, the alternate stack appears to be still in use, and the system chooses the original stack for the second call to the signal handler -- which trips our assertion asking to verify that the signal handler is always using an alternate stack. Not strictly necessary for the signal handler to use an alternate stack on re-entry, but this makes it clearer that the signal handler itself is always using the alternate stack so we can verify that the interrupted code is _not_ in the signal handler. With this change, the test now passes on aarch64. PR lib/57946
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riastradh
parent
81899325cc
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9ba2d744e7
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@ -1,4 +1,4 @@
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/* $NetBSD: t_sigstack.c,v 1.5 2024/02/19 12:41:27 riastradh Exp $ */
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/* $NetBSD: t_sigstack.c,v 1.6 2024/02/19 13:34:48 riastradh Exp $ */
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/*-
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* Copyright (c) 2024 The NetBSD Foundation, Inc.
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@ -27,7 +27,7 @@
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: t_sigstack.c,v 1.5 2024/02/19 12:41:27 riastradh Exp $");
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__RCSID("$NetBSD: t_sigstack.c,v 1.6 2024/02/19 13:34:48 riastradh Exp $");
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#include <setjmp.h>
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#include <signal.h>
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@ -37,7 +37,7 @@ __RCSID("$NetBSD: t_sigstack.c,v 1.5 2024/02/19 12:41:27 riastradh Exp $");
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#include "h_macros.h"
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struct sigaltstack ss;
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struct sigaltstack ss[3];
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jmp_buf jmp;
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sigjmp_buf sigjmp;
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unsigned nentries;
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@ -50,28 +50,33 @@ on_sigusr1(int signo, siginfo_t *si, void *ctx)
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ucontext_t *uc = ctx;
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void *sp = (void *)(uintptr_t)_UC_MACHINE_SP(uc);
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void *fp = __builtin_frame_address(0);
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struct sigaltstack *ssp;
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/*
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* Ensure we haven't re-entered the signal handler too many
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* times. We should enter only twice.
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*/
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ATF_REQUIRE_MSG(nentries < 2,
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"%u recursive signal handler entries is too many in this test",
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nentries + 1);
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/*
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* Ensure that the signal handler was called in the alternate
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* signal stack.
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*/
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ATF_REQUIRE_MSG(fp >= ss.ss_sp,
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ssp = &ss[nentries];
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ATF_REQUIRE_MSG((fp >= ssp->ss_sp &&
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fp < (void *)((char *)ssp->ss_sp + ssp->ss_size)),
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"sigaltstack failed to take effect on entry %u --"
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" signal handler's frame pointer %p doesn't lie in sigaltstack"
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" [%p, %p), size 0x%zx",
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nentries,
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fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size);
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ATF_REQUIRE_MSG(fp < (void *)((char *)ss.ss_sp + ss.ss_size),
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"sigaltstack failed to take effect on entry %u --"
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" signal handler's frame pointer %p doesn't lie in sigaltstack"
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" [%p, %p), size 0x%zx",
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nentries,
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fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size);
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fp, ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size, ssp->ss_size);
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/*
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* Ensure that if we enter the signal handler, we are entering
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* it from the original stack, not from the alternate signal
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* stack.
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* it from the original stack, not from any of the alternate
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* signal stacks.
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*
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* On some architectures, this is broken. Those that appear to
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* get this right are:
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@ -84,13 +89,19 @@ on_sigusr1(int signo, siginfo_t *si, void *ctx)
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if (nentries > 0)
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atf_tc_expect_fail("PR lib/57946");
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#endif
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ATF_REQUIRE_MSG((sp < ss.ss_sp ||
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sp > (void *)((char *)ss.ss_sp + ss.ss_size)),
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"%s failed to restore stack before allowing signal on entry %u--"
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" interrupted stack pointer %p lies in sigaltstack"
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" [%p, %p), size 0x%zx",
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nentries,
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bailname, sp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size);
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for (ssp = &ss[0]; ssp < &ss[__arraycount(ss)]; ssp++) {
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ATF_REQUIRE_MSG((sp < ssp->ss_sp ||
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sp > (void *)((char *)ssp->ss_sp + ssp->ss_size)),
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"%s failed to restore stack"
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" before allowing signal on entry %u --"
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" interrupted stack pointer %p lies in sigaltstack %zd"
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" [%p, %p), size 0x%zx",
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bailname,
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nentries,
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sp, ssp - ss,
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ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size,
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ssp->ss_size);
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}
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/*
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* First time through, we want to test whether longjmp restores
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@ -103,6 +114,15 @@ on_sigusr1(int signo, siginfo_t *si, void *ctx)
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if (nentries++ == 0)
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RL(raise(SIGUSR1));
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/*
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* Set up the next sigaltstack. We can't reuse the current one
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* for the next signal handler re-entry until the system clears
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* the SS_ONSTACK process state -- which normal return from
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* signal handler does, but which longjmp does not. So to keep
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* it simple (ha), we just use another sigaltstack.
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*/
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RL(sigaltstack(&ss[nentries], NULL));
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/*
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* Jump back to the original context.
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*/
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@ -113,19 +133,22 @@ static void
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go(const char *name, void (*fn)(void) __dead)
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{
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struct sigaction sa;
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unsigned i;
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bailname = name;
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bailfn = fn;
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/*
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* Allocate a stack for the signal handler to run in, and
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* configure the system to use it.
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* configure the system to use the first one.
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*
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* XXX Should maybe use a guard page but this is simpler.
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*/
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ss.ss_size = SIGSTKSZ;
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REQUIRE_LIBC(ss.ss_sp = malloc(ss.ss_size), NULL);
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RL(sigaltstack(&ss, NULL));
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for (i = 0; i < __arraycount(ss); i++) {
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ss[i].ss_size = SIGSTKSZ;
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REQUIRE_LIBC(ss[i].ss_sp = malloc(ss[i].ss_size), NULL);
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}
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RL(sigaltstack(&ss[0], NULL));
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/*
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* Set up a test signal handler for SIGUSR1. Allow all
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