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tests: Move alternate stack onto the heap rather than the main stack

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And size it to `sysconf (_SC_MINSIGSTKSZ)`, if defined.

This might fix the sigaltstack test on muslc, as suggested by Markus
Wichmann (https://www.openwall.com/lists/musl/2024/05/30/2) and Rich Felker
(https://www.openwall.com/lists/musl/2024/05/29/7) on the musl mailing
list.

The thinking is that the CI machine might have a huge register file
(AVX512 or some other large extension) which doesn’t fit in `MINSIGSTKSZ`.
By sizing the alternate stack to `sysconf (_SC_MINSIGSTKSZ)` we should
be able to avoid that.

Moving it onto the heap should avoid any potential complications or bugs
from having one stack embedded within another.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Fixes: #3315
This commit is contained in:
Philip Withnall 2024-08-16 14:13:12 +01:00
parent f4aceb0e91
commit 84728d4e01
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1 changed files with 31 additions and 11 deletions
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42
glib/tests/unix.c
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@ -588,14 +588,27 @@ test_signal_alternate_stack (int signal)
#ifndef SA_ONSTACK
g_test_skip ("alternate stack is not supported");
#else
guint8 stack_memory[MINSIGSTKSZ];
guint8 zero_mem[MINSIGSTKSZ];
stack_t stack = { .ss_sp = stack_memory, .ss_size = MINSIGSTKSZ };
size_t minsigstksz = MINSIGSTKSZ;
guint8 *stack_memory = NULL;
guint8 *zero_mem = NULL;
stack_t stack = { 0 };
stack_t old_stack = { 0 };
memset (stack_memory, 0, MINSIGSTKSZ);
memset (zero_mem, 0, MINSIGSTKSZ);
g_assert_cmpmem (stack_memory, MINSIGSTKSZ, zero_mem, MINSIGSTKSZ);
#ifdef _SC_MINSIGSTKSZ
/* Use the kernel-provided minimum stack size, if available. Otherwise default
* to MINSIGSTKSZ. Unfortunately that might not be big enough for huge
* register files for big CPU instruction set extensions. */
minsigstksz = sysconf (_SC_MINSIGSTKSZ);
if (minsigstksz == (size_t) -1 || minsigstksz < (size_t) MINSIGSTKSZ)
minsigstksz = MINSIGSTKSZ;
#endif
stack_memory = g_malloc0 (minsigstksz);
zero_mem = g_malloc0 (minsigstksz);
g_assert_cmpmem (stack_memory, minsigstksz, zero_mem, minsigstksz);
stack.ss_sp = stack_memory;
stack.ss_size = minsigstksz;
g_assert_no_errno (sigaltstack (&stack, &old_stack));
@ -620,6 +633,10 @@ test_signal_alternate_stack (int signal)
stack.ss_flags = SS_DISABLE;
g_assert_no_errno (sigaltstack (&stack, &old_stack));
g_free (zero_mem);
g_free (stack_memory);
return;
}
#endif
@ -627,20 +644,23 @@ test_signal_alternate_stack (int signal)
/* Very stupid check to ensure that the alternate stack is used instead of
* the default one. This test would fail if SA_ONSTACK wouldn't be set.
*/
g_assert_cmpint (memcmp (stack_memory, zero_mem, MINSIGSTKSZ), !=, 0);
g_assert_cmpint (memcmp (stack_memory, zero_mem, minsigstksz), !=, 0);
/* We need to memset again zero_mem since compiler may have optimized it out
* as we've seen in freebsd CI.
*/
memset (zero_mem, 0, MINSIGSTKSZ);
memset (stack_memory, 0, MINSIGSTKSZ);
g_assert_cmpmem (stack_memory, MINSIGSTKSZ, zero_mem, MINSIGSTKSZ);
memset (zero_mem, 0, minsigstksz);
memset (stack_memory, 0, minsigstksz);
g_assert_cmpmem (stack_memory, minsigstksz, zero_mem, minsigstksz);
stack.ss_flags = SS_DISABLE;
g_assert_no_errno (sigaltstack (&stack, &old_stack));
test_signal (signal);
g_assert_cmpmem (stack_memory, MINSIGSTKSZ, zero_mem, MINSIGSTKSZ);
g_assert_cmpmem (stack_memory, minsigstksz, zero_mem, minsigstksz);
g_free (zero_mem);
g_free (stack_memory);
#endif
}