From f6a65c23356574113f91060f82cef2119af4949a Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 17 Jul 2008 06:23:47 -0600 Subject: [PATCH] Make c-stack use libsigsegv, when available. * modules/c-stack (Depends-on): Add libsigsegv. * modules/c-stack-tests (Makefile.am): Link with libsigsegv, if needed. * lib/c-stack.c (SIGSTKSZ): Define fallback. (segv_handler, overflow_handler, c_stack_action) [HAVE_LIBSIGSEGV && !HAVE_XSI_STACK_OVERFLOW_HEURISTIC]: Add new implementation when libsigsegv is available, but only when using the library is necessary. * m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Add comment, explaining why XSI check fails on Linux. (gl_PREREQ_C_STACK): Supply LIBCSTACK, LTLIBCSTACK. * tests/test-c-stack2.sh: Tweak skip message. * NEWS: Document new link-time requirements. Signed-off-by: Eric Blake --- ChangeLog | 17 ++++++ NEWS | 4 ++ lib/c-stack.c | 150 +++++++++++++++++++++++++++++++++++++++++-------- m4/c-stack.m4 | 16 +++++- modules/c-stack | 4 ++ modules/c-stack-tests | 2 +- tests/test-c-stack2.sh | 2 +- 7 files changed, 169 insertions(+), 26 deletions(-) diff --git a/ChangeLog b/ChangeLog index 0772f2d80..01f00842c 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,20 @@ +2008-07-17 Eric Blake + + Make c-stack use libsigsegv, when available. + * modules/c-stack (Depends-on): Add libsigsegv. + * modules/c-stack-tests (Makefile.am): Link with libsigsegv, if + needed. + * lib/c-stack.c (SIGSTKSZ): Define fallback. + (segv_handler, overflow_handler, c_stack_action) + [HAVE_LIBSIGSEGV && !HAVE_XSI_STACK_OVERFLOW_HEURISTIC]: Add new + implementation when libsigsegv is available, but only when using + the library is necessary. + * m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Add + comment, explaining why XSI check fails on Linux. + (gl_PREREQ_C_STACK): Supply LIBCSTACK, LTLIBCSTACK. + * tests/test-c-stack2.sh: Tweak skip message. + * NEWS: Document new link-time requirements. + 2008-07-16 Eric Blake c-stack: Expose false positives when not using libsigsegv. diff --git a/NEWS b/NEWS index 74ca23494..da75d7f83 100644 --- a/NEWS +++ b/NEWS @@ -6,6 +6,10 @@ User visible incompatible changes Date Modules Changes +2008-07-17 c-stack The module now requires the addition of + $(LIBCSTACK) or $(LTLIBCSTACK) in Makefile.am, + since it may depend on linking with libsigsegv. + 2008-07-07 isnanf-nolibm The include file is changed from "isnanf.h" to "isnanf-nolibm.h". isnand-nolibm The include file is changed from "isnand.h" diff --git a/lib/c-stack.c b/lib/c-stack.c index 96bd2bf60..c81fbfa78 100644 --- a/lib/c-stack.c +++ b/lib/c-stack.c @@ -53,6 +53,9 @@ #if ! HAVE_STACK_T && ! defined stack_t typedef struct sigaltstack stack_t; #endif +#ifndef SIGSTKSZ +# define SIGSTKSZ 16384 +#endif #include #include @@ -68,6 +71,10 @@ typedef struct sigaltstack stack_t; # define STDERR_FILENO 2 #endif +#if HAVE_LIBSIGSEGV +# include +#endif + #include "c-stack.h" #include "exitfail.h" @@ -110,7 +117,115 @@ die (int signo) abort (); } -#if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK +#if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) || HAVE_LIBSIGSEGV + +/* Storage for the alternate signal stack. */ +static union +{ + char buffer[SIGSTKSZ]; + + /* These other members are for proper alignment. There's no + standard way to guarantee stack alignment, but this seems enough + in practice. */ + long double ld; + long l; + void *p; +} alternate_signal_stack; + +static void +null_action (int signo __attribute__ ((unused))) +{ +} + +#endif /* SIGALTSTACK || LIBSIGSEGV */ + +/* Only use libsigsegv if we need it; platforms like Solaris can + detect stack overflow without the overhead of an external + library. */ +#if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC + +/* Nonzero if general segv handler could not be installed. */ +static volatile int segv_handler_missing; + +/* Handle a segmentation violation and exit if it cannot be stack + overflow. This function is async-signal-safe. */ + +static int segv_handler (void *address __attribute__ ((unused)), + int serious) +{ +# if DEBUG + { + char buf[1024]; + sprintf (buf, "segv_handler serious=%d\n", serious); + write (STDERR_FILENO, buf, strlen (buf)); + } +# endif + + /* If this fault is not serious, return 0 to let the stack overflow + handler take a shot at it. */ + if (!serious) + return 0; + die (SIGSEGV); +} + +/* Handle a segmentation violation that is likely to be a stack + overflow and exit. This function is async-signal-safe. */ + +static void overflow_handler (int, stackoverflow_context_t) + __attribute__ ((noreturn)); +static void +overflow_handler (int emergency, + stackoverflow_context_t context __attribute__ ((unused))) +{ +# if DEBUG + { + char buf[1024]; + sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n", + emergency, segv_handler_missing); + write (STDERR_FILENO, buf, strlen (buf)); + } +# endif + + die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV); +} + +/* Set up ACTION so that it is invoked on C stack overflow. Return -1 + (setting errno) if this cannot be done. + + When ACTION is called, it is passed an argument equal to SIGSEGV + for a segmentation violation that does not appear related to stack + overflow, and is passed zero otherwise. On many platforms it is + hard to tell; when in doubt, zero is passed. + + A null ACTION acts like an action that does nothing. + + ACTION must be async-signal-safe. ACTION together with its callees + must not require more than SIGSTKSZ bytes of stack space. Also, + ACTION should not call longjmp, because this implementation does + not guarantee that it is safe to return to the original stack. */ + +int +c_stack_action (void (*action) (int)) +{ + segv_action = action ? action : null_action; + program_error_message = _("program error"); + stack_overflow_message = _("stack overflow"); + + /* Always install the overflow handler. */ + if (stackoverflow_install_handler (overflow_handler, + alternate_signal_stack.buffer, + sizeof alternate_signal_stack.buffer)) + { + errno = ENOTSUP; + return -1; + } + /* Try installing a general handler; if it fails, then treat all + segv as stack overflow. */ + segv_handler_missing = sigsegv_install_handler (segv_handler); + return 0; +} + +#elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK /* Direction of the C runtime stack. This function is async-signal-safe. */ @@ -126,19 +241,6 @@ find_stack_direction (char const *addr) } # endif -/* Storage for the alternate signal stack. */ -static union -{ - char buffer[SIGSTKSZ]; - - /* These other members are for proper alignment. There's no - standard way to guarantee stack alignment, but this seems enough - in practice. */ - long double ld; - long l; - void *p; -} alternate_signal_stack; - # if SIGACTION_WORKS /* Handle a segmentation violation and exit. This function is @@ -155,7 +257,14 @@ segv_handler (int signo, siginfo_t *info, # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC /* We can't easily determine whether it is a stack overflow; so assume that the rest of our program is perfect (!) and that - this segmentation violation is a stack overflow. */ + this segmentation violation is a stack overflow. + + Note that although both Linux and Solaris provide + sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only + Solaris satisfies the XSI heueristic. This is because + Solaris populates uc_stack with the details of the + interrupted stack, while Linux populates it with the details + of the current stack. */ signo = 0; # else /* If the faulting address is within the stack, or within one @@ -189,11 +298,6 @@ segv_handler (int signo, siginfo_t *info, } # endif -static void -null_action (int signo __attribute__ ((unused))) -{ -} - /* Set up ACTION so that it is invoked on C stack overflow. Return -1 (setting errno) if this cannot be done. @@ -205,7 +309,9 @@ null_action (int signo __attribute__ ((unused))) A null ACTION acts like an action that does nothing. ACTION must be async-signal-safe. ACTION together with its callees - must not require more than SIGSTKSZ bytes of stack space. */ + must not require more than SIGSTKSZ bytes of stack space. Also, + ACTION should not call longjmp, because this implementation does + not guarantee that it is safe to return to the original stack. */ int c_stack_action (void (*action) (int)) @@ -240,7 +346,7 @@ c_stack_action (void (*action) (int)) return sigaction (SIGSEGV, &act, NULL); } -#else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */ +#else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) || HAVE_LIBSIGSEGV) */ int c_stack_action (void (*action) (int) __attribute__ ((unused))) diff --git a/m4/c-stack.m4 b/m4/c-stack.m4 index f14217145..b1f93eda8 100644 --- a/m4/c-stack.m4 +++ b/m4/c-stack.m4 @@ -7,7 +7,7 @@ # Written by Paul Eggert. -# serial 2 +# serial 3 AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC], [# for STACK_DIRECTION @@ -55,6 +55,9 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC], { if (0 < info->si_code) { + /* For XSI heuristics to work, we need uc_stack to describe + the interrupted stack (as on Solaris), and not the + currently executing stack (as on Linux). */ ucontext_t const *user_context = context; char const *stack_min = user_context->uc_stack.ss_sp; size_t stack_size = user_context->uc_stack.ss_size; @@ -133,6 +136,7 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC], AC_DEFUN([gl_PREREQ_C_STACK], [AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC]) + AC_REQUIRE([gl_LIBSIGSEGV]) # for STACK_DIRECTION AC_REQUIRE([AC_FUNC_ALLOCA]) @@ -144,7 +148,15 @@ AC_DEFUN([gl_PREREQ_C_STACK], AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , , [#include ]) - AC_CHECK_TYPES([stack_t], , , [#include ])]) + AC_CHECK_TYPES([stack_t], , , [#include ]) + + dnl c-stack does not need -lsigsegv if the system has XSI heuristics. + if test "$gl_cv_lib_sigsegv" = yes \ + && test $"ac_cv_sys_xsi_stack_overflow_heuristic" != yes ; then + AC_SUBST([LIBCSTACK], [$LIBSIGSEGV]) + AC_SUBST([LTLIBCSTACK], [$LTLIBSIGSEGV]) + fi +]) AC_DEFUN([gl_C_STACK], [ diff --git a/modules/c-stack b/modules/c-stack index d3e7e0996..a01b8c785 100644 --- a/modules/c-stack +++ b/modules/c-stack @@ -12,6 +12,7 @@ exitfail unistd raise sigaction +libsigsegv configure.ac: gl_C_STACK @@ -22,6 +23,9 @@ lib_SOURCES += c-stack.h c-stack.c Include: "c-stack.h" +Link: +$(LTCSTACK) when linking with libtool, $(LIBCSTACK) otherwise + License: GPL diff --git a/modules/c-stack-tests b/modules/c-stack-tests index 5d3bc5807..4cf15f211 100644 --- a/modules/c-stack-tests +++ b/modules/c-stack-tests @@ -12,5 +12,5 @@ Makefile.am: TESTS += test-c-stack.sh test-c-stack2.sh TESTS_ENVIRONMENT += EXEEXT='@EXEEXT@' check_PROGRAMS += test-c-stack -test_c_stack_LDADD = $(LDADD) @LIBINTL@ +test_c_stack_LDADD = $(LDADD) $(LIBCSTACK) @LIBINTL@ MOSTLYCLEANFILES += t-c-stack.tmp t-c-stack2.tmp diff --git a/tests/test-c-stack2.sh b/tests/test-c-stack2.sh index e55ff172d..039a81976 100755 --- a/tests/test-c-stack2.sh +++ b/tests/test-c-stack2.sh @@ -11,7 +11,7 @@ tmpfiles="t-c-stack2.tmp" case $? in 77) if grep 'stack overflow' t-c-stack2.tmp >/dev/null ; then - echo 'cannot distinguish stack overflow from crash' >&2 + echo 'cannot tell stack overflow from crash; consider installing libsigsegv' >&2 else cat t-c-stack2.tmp >&2 fi -- 2.11.0