diff options
Diffstat (limited to 'lib/libkse/thread/thr_private.h')
| -rw-r--r-- | lib/libkse/thread/thr_private.h | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/lib/libkse/thread/thr_private.h b/lib/libkse/thread/thr_private.h index 4326bf6..8a126f4 100644 --- a/lib/libkse/thread/thr_private.h +++ b/lib/libkse/thread/thr_private.h @@ -335,7 +335,13 @@ struct pthread_attr { * Miscellaneous definitions. */ #define PTHREAD_STACK_DEFAULT 65536 -/* Size of red zone at the end of each stack. */ +/* + * Size of red zone at the end of each stack. In actuality, this "red zone" is + * merely an unmapped region, except in the case of the initial stack. Since + * mmap() makes it possible to specify the maximum growth of a MAP_STACK region, + * an unmapped gap between thread stacks achieves the same effect as explicitly + * mapped red zones. + */ #define PTHREAD_STACK_GUARD PAGE_SIZE /* @@ -904,10 +910,17 @@ SCLASS pthread_switch_routine_t _sched_switch_hook */ SCLASS SLIST_HEAD(, stack) _stackq; -/* Base address of next unallocated default-size stack. Stacks are allocated - * contiguously, starting below the beginning of the main stack. When a new - * stack is created, a guard page is created just above it in order to (usually) - * detect attempts by the adjacent stack to trounce the next thread stack. */ +/* + * Base address of next unallocated default-size {stack, red zone}. Stacks are + * allocated contiguously, starting below the bottom of the main stack. When a + * new stack is created, a red zone is created (actually, the red zone is simply + * left unmapped) below the bottom of the stack, such that the stack will not be + * able to grow all the way to the top of the next stack. This isn't + * fool-proof. It is possible for a stack to grow by a large amount, such that + * it grows into the next stack, and as long as the memory within the red zone + * is never accessed, nothing will prevent one thread stack from trouncing all + * over the next. + */ SCLASS void * _next_stack #ifdef GLOBAL_PTHREAD_PRIVATE /* main stack top - main stack size - stack size - (red zone + main stack red zone) */ |
