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Based on the following commits:
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commit 2c41b52901331f5c761015af786a3976e225d779
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Jun 13 13:08:39 2016 +0200
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debug/tst-longjmp_chk2: Make signal handler more conservative [BZ #20248]
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Currently, printf needs more stack space than what is available with
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SIGSTKSZ. This commit use the the write system call directly instead.
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Also use sig_atomic_t for the “pass” variable (for general
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correctness), and restore signal handlers to their defaults, to avoid
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masking crashes.
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commit 5896c8bdd9f73cdc816a96e107ca1f7a6bc6921e
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Author: Mike Frysinger <vapier@gentoo.org>
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Date: Sun Dec 29 16:30:35 2013 -0500
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tst-longjmp_chk2: add comments/sanity check
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If the longjmp checking code is slightly broken, this code can loop
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forever which isn't too helpful. Add a sanity check to keep that
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from happening.
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Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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Index: b/debug/tst-longjmp_chk2.c
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===================================================================
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--- a/debug/tst-longjmp_chk2.c
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+++ b/debug/tst-longjmp_chk2.c
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@@ -4,27 +4,36 @@
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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+#include <string.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/resource.h>
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+#include <unistd.h>
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static jmp_buf mainloop;
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static sigset_t mainsigset;
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-static int pass;
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+static volatile sig_atomic_t pass;
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+static void
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+write_message (const char *message)
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+{
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+ ssize_t unused __attribute__ ((unused));
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+ for (int i = 0; i < pass; ++i)
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+ unused = write (STDOUT_FILENO, " ", 1);
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+ unused = write (STDOUT_FILENO, message, strlen (message));
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+}
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static void
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stackoverflow_handler (int sig)
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{
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stack_t altstack;
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pass++;
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+ assert (pass < 5);
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sigaltstack (NULL, &altstack);
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- /* Using printf is not really kosher in signal handlers but we know
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- it will work. */
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- printf ("%*sin signal handler\n", pass, "");
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+ write_message ("in signal handler\n");
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if (altstack.ss_flags & SS_ONSTACK)
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- printf ("%*son alternate stack\n", pass, "");
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+ write_message ("on alternate stack\n");
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siglongjmp (mainloop, pass);
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}
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@@ -107,6 +116,11 @@ do_test (void)
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else
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printf ("disabling alternate stack succeeded \n");
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+ /* Restore the signal handlers, in case we trigger a crash after the
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+ tests above. */
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+ signal (SIGBUS, SIG_DFL);
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+ signal (SIGSEGV, SIG_DFL);
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+
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return 0;
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}
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