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Improve stack overflow diagnostics (take 2).

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This reverts commits eb1b07469f and
d14dc3b87f, and fixes the bug where
we were calling mmap (which might cause errno to be set) before
__set_tls (which is required to implement errno).

Bug: 8557703
Change-Id: I2c36d00240c56e156e1bb430d8c22a73a068b70c
This commit is contained in:
Elliott Hughes
2013-07-17 13:33:19 -07:00
parent 40e7a87864
commit 84114c8dd5
5 changed files with 74 additions and 33 deletions
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23
libc/bionic/pthread_create.cpp
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@@ -69,9 +69,22 @@ void __init_tls(pthread_internal_t* thread) {
thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard;
__set_tls(thread->tls);
// Create and set an alternate signal stack.
// This must happen after __set_tls, in case a system call fails and tries to set errno.
stack_t ss;
ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
if (ss.ss_sp != MAP_FAILED) {
ss.ss_size = SIGSTKSZ;
ss.ss_flags = 0;
sigaltstack(&ss, NULL);
thread->alternate_signal_stack = ss.ss_sp;
}
}
// This trampoline is called from the assembly _pthread_clone() function.
// This trampoline is called from the assembly _pthread_clone function.
// Our 'tls' and __pthread_clone's 'child_stack' are one and the same, just growing in
// opposite directions.
extern "C" void __thread_entry(void* (*func)(void*), void* arg, void** tls) {
// Wait for our creating thread to release us. This lets it have time to
// notify gdb about this thread before we start doing anything.
@@ -187,8 +200,12 @@ int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr,
thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_STACK;
}
// Make room for TLS.
// Make room for the TLS area.
// The child stack is the same address, just growing in the opposite direction.
// At offsets >= 0, we have the TLS slots.
// At offsets < 0, we have the child stack.
void** tls = (void**)((uint8_t*)(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*));
void* child_stack = tls;
// Create a mutex for the thread in TLS_SLOT_SELF to wait on once it starts so we can keep
// it from doing anything until after we notify the debugger about it
@@ -204,7 +221,7 @@ int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr,
int flags = CLONE_FILES | CLONE_FS | CLONE_VM | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM;
int tid = __pthread_clone(start_routine, tls, flags, arg);
int tid = __pthread_clone(start_routine, child_stack, flags, arg);
if (tid < 0) {
int clone_errno = errno;
if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_STACK) == 0) {