107 lines
4.1 KiB
Diff
107 lines
4.1 KiB
Diff
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c-stack: stop using SIGSTKSZ
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It’s been proposed to stop making SIGSTKSZ an integer constant:
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https://sourceware.org/pipermail/libc-alpha/2020-September/118028.html
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Also, using SIGSTKSZ in #if did not conform to current POSIX.
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Also, avoiding SIGSTKSZ makes the code simpler and easier to grok.
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* lib/c-stack.c (SIGSTKSZ): Remove.
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(alternate_signal_stack): Now a 64 KiB array, for simplicity.
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All uses changed.
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[Retrieved (and backported) from:
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https://git.savannah.gnu.org/cgit/gnulib.git/patch/?id=f9e2b20a12a230efa30f1d479563ae07d276a94b]
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Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
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diff -Nura m4-1.4.18.orig/lib/c-stack.c m4-1.4.18/lib/c-stack.c
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--- m4-1.4.18.orig/lib/c-stack.c 2021-04-11 19:12:14.086494029 +0200
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+++ m4-1.4.18/lib/c-stack.c 2021-04-11 19:48:46.316862760 +0200
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@@ -50,15 +50,16 @@
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#if ! HAVE_STACK_T && ! defined stack_t
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typedef struct sigaltstack stack_t;
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#endif
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-#ifndef SIGSTKSZ
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-# define SIGSTKSZ 16384
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-#elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
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-/* libsigsegv 2.6 through 2.8 have a bug where some architectures use
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- more than the Linux default of an 8k alternate stack when deciding
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- if a fault was caused by stack overflow. */
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-# undef SIGSTKSZ
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-# define SIGSTKSZ 16384
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-#endif
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+
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+/* Storage for the alternate signal stack.
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+ 64 KiB is not too large for Gnulib-using apps, and is large enough
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+ for all known platforms. Smaller sizes may run into trouble.
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+ For example, libsigsegv 2.6 through 2.8 have a bug where some
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+ architectures use more than the Linux default of an 8 KiB alternate
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+ stack when deciding if a fault was caused by stack overflow. */
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+static max_align_t alternate_signal_stack[(64 * 1024
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+ + sizeof (max_align_t) - 1)
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+ / sizeof (max_align_t)];
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#include <stdlib.h>
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#include <string.h>
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@@ -128,19 +129,6 @@
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#if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK \
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&& HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV
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-/* Storage for the alternate signal stack. */
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-static union
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-{
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- char buffer[SIGSTKSZ];
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-
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- /* These other members are for proper alignment. There's no
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- standard way to guarantee stack alignment, but this seems enough
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- in practice. */
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- long double ld;
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- long l;
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- void *p;
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-} alternate_signal_stack;
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-
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static void
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null_action (int signo __attribute__ ((unused)))
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{
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@@ -205,8 +193,8 @@
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/* Always install the overflow handler. */
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if (stackoverflow_install_handler (overflow_handler,
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- alternate_signal_stack.buffer,
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- sizeof alternate_signal_stack.buffer))
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+ alternate_signal_stack,
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+ sizeof alternate_signal_stack))
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{
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errno = ENOTSUP;
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return -1;
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@@ -279,14 +267,14 @@
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stack_t st;
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struct sigaction act;
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st.ss_flags = 0;
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+ st.ss_sp = alternate_signal_stack;
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+ st.ss_size = sizeof alternate_signal_stack;
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# if SIGALTSTACK_SS_REVERSED
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/* Irix mistakenly treats ss_sp as the upper bound, rather than
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lower bound, of the alternate stack. */
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- st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
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- st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
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-# else
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- st.ss_sp = alternate_signal_stack.buffer;
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- st.ss_size = sizeof alternate_signal_stack.buffer;
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+ st.ss_size -= sizeof (void *);
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+ char *ss_sp = st.ss_sp;
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+ st.ss_sp = ss_sp + st.ss_size;
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# endif
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r = sigaltstack (&st, NULL);
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if (r != 0)
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diff -Nura m4-1.4.18.orig/lib/c-stack.h m4-1.4.18/lib/c-stack.h
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--- m4-1.4.18.orig/lib/c-stack.h 2021-04-11 19:12:14.098494042 +0200
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+++ m4-1.4.18/lib/c-stack.h 2021-04-11 19:17:42.138848378 +0200
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@@ -34,7 +34,7 @@
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A null ACTION acts like an action that does nothing.
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ACTION must be async-signal-safe. ACTION together with its callees
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- must not require more than SIGSTKSZ bytes of stack space. Also,
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+ must not require more than 64 KiB bytes of stack space. Also,
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ACTION should not call longjmp, because this implementation does
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not guarantee that it is safe to return to the original stack.
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