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Work around CLONE_SETTLS being weird on x86.

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Unlike other architectures, on x86 (but not x86-64), CLONE_SETTLS
takes a pointer to a struct user_desc instead of a pointer to the
TLS itself. Rather than have to deal with this here, let's just use
the old __set_tls mechanism we used to use (and still use for the
main thread on all architectures, so it's not going away any time
soon).

Bug: 11826724
Change-Id: I02a27939a73ae6cea1134a3f4c1dd7eafea479da
This commit is contained in:
Elliott Hughes
2013-11-26 13:57:21 -08:00
parent 1c057607d8
commit 80906141f7
1 changed files with 11 additions and 0 deletions
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11
libc/bionic/pthread_create.cpp
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@@ -41,6 +41,7 @@
#include "private/ScopedPthreadMutexLocker.h"
extern "C" pid_t __bionic_clone(uint32_t flags, void* child_stack, int* parent_tid, void* tls, int* child_tid, int (*fn)(void*), void* arg);
extern "C" int __set_tls(void*);
#ifdef __i386__
#define ATTRIBUTES __attribute__((noinline)) __attribute__((fastcall))
@@ -61,6 +62,10 @@ void __init_tls(pthread_internal_t* thread) {
thread->tls[i] = NULL;
}
#if defined(__i386__)
__set_tls(thread->tls);
#endif
// Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0.
thread->tls[TLS_SLOT_SELF] = thread->tls;
thread->tls[TLS_SLOT_THREAD_ID] = thread;
@@ -225,6 +230,12 @@ int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr,
int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID;
#if defined(__i386__)
// On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than
// a pointer to the TLS itself. Rather than try to deal with that here, we just let x86 set
// the TLS manually in __init_tls, like all architectures used to.
flags &= ~CLONE_SETTLS;
#endif
int rc = __bionic_clone(flags, child_stack, &(thread->tid), thread->tls, &(thread->tid), __pthread_start, thread);
if (rc == -1) {
int clone_errno = errno;