diff options
Diffstat (limited to 'libpthread/linuxthreads/manager.c')
| -rw-r--r-- | libpthread/linuxthreads/manager.c | 35 |
1 files changed, 30 insertions, 5 deletions
diff --git a/libpthread/linuxthreads/manager.c b/libpthread/linuxthreads/manager.c index 2a1ee62af..122997b10 100644 --- a/libpthread/linuxthreads/manager.c +++ b/libpthread/linuxthreads/manager.c @@ -47,6 +47,15 @@ # define USE_SELECT #endif +/* MAP_FIXED_NOREPLACE is not supported in kernel <= 4.17 + * If it's not already defined, define it to 0. + * We check the results of mmap to ensure the correct + * results, and error out otherwise. + */ +#ifndef MAP_FIXED_NOREPLACE +#define MAP_FIXED_NOREPLACE 0 +#endif + /* Array of active threads. Entry 0 is reserved for the initial thread. */ struct pthread_handle_struct __pthread_handles[PTHREAD_THREADS_MAX] = { { __LOCK_INITIALIZER, &__pthread_initial_thread, 0}, @@ -371,12 +380,19 @@ static int pthread_allocate_stack(const pthread_attr_t *attr, /* Allocate space for stack and thread descriptor at default address */ new_thread = default_new_thread; new_thread_bottom = (char *) (new_thread + 1) - stacksize; - if (mmap((caddr_t)((char *)(new_thread + 1) - INITIAL_STACK_SIZE), + void * new_stack_addr = NULL; + new_stack_addr = mmap((caddr_t)((char *)(new_thread + 1) - INITIAL_STACK_SIZE), INITIAL_STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, - MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | MAP_GROWSDOWN, - -1, 0) == MAP_FAILED) + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE | MAP_GROWSDOWN, + -1, 0); + if (new_stack_addr == MAP_FAILED){ /* Bad luck, this segment is already mapped. */ return -1; + } else if ( new_stack_addr != (caddr_t)((char *)(new_thread + 1) - INITIAL_STACK_SIZE)) { + /* Worse luck, we almost overwrote an existing page */ + munmap(new_stack_addr, INITIAL_STACK_SIZE); + return -2; + } /* We manage to get a stack. Now see whether we need a guard and allocate it if necessary. Notice that the default attributes (stack_size = STACK_SIZE - pagesize) do not need @@ -496,9 +512,10 @@ static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr, return EAGAIN; if (__pthread_handles[sseg].h_descr != NULL) continue; - if (pthread_allocate_stack(attr, thread_segment(sseg), pagesize, + int res = pthread_allocate_stack(attr, thread_segment(sseg), pagesize, &new_thread, &new_thread_bottom, - &guardaddr, &guardsize) == 0) + &guardaddr, &guardsize); + if ( res == 0) break; #ifndef __ARCH_USE_MMU__ else @@ -507,6 +524,14 @@ static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr, * use the next one. However, when there is no MMU, malloc () is used. * It's waste of CPU cycles to continue to try if it fails. */ return EAGAIN; +#else + else if (res == -2) + /* When there is an MMU, if pthread_allocate_stack failed with -2, + * it indicates that we are attempting to mmap in address space which + * is already allocated. Any additional attempts will result in failure + * since we have exhausted our stack area. + */ + return EAGAIN; #endif } __pthread_handles_num++; |