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rt: Add rust_task::get_task_from_tcb

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This commit is contained in:
Brian Anderson 2012-03-21 14:15:30 -07:00
parent 08f783ff10
commit 4ad57f5c39
1 changed files with 35 additions and 6 deletions
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41
src/rt/rust_task.h
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@ -61,6 +61,18 @@
#endif
#endif
extern "C" CDECL void
record_sp_limit(void *limit);
extern "C" CDECL uintptr_t
get_sp_limit();
// The function prolog compares the amount of stack needed to the end of
// the stack. As an optimization, when the frame size is less than 256
// bytes, it will simply compare %esp to to the stack limit instead of
// subtracting the frame size. As a result we need our stack limit to
// account for those 256 bytes.
const unsigned LIMIT_OFFSET = 256;
struct rust_box;
struct frame_glue_fns {
@ -257,6 +269,7 @@ public:
const char *get_cond_name() { return cond_name; }
void cleanup_after_turn();
static rust_task *get_task_from_tcb();
};
// This stuff is on the stack-switching fast path
@ -432,12 +445,6 @@ record_sp_limit(void *limit);
inline void
rust_task::record_stack_limit() {
I(thread, stk);
// The function prolog compares the amount of stack needed to the end of
// the stack. As an optimization, when the frame size is less than 256
// bytes, it will simply compare %esp to to the stack limit instead of
// subtracting the frame size. As a result we need our stack limit to
// account for those 256 bytes.
const unsigned LIMIT_OFFSET = 256;
A(thread,
(uintptr_t)stk->end - RED_ZONE_SIZE
- (uintptr_t)stk->data >= LIMIT_OFFSET,
@ -445,6 +452,28 @@ rust_task::record_stack_limit() {
record_sp_limit(stk->data + LIMIT_OFFSET + RED_ZONE_SIZE);
}
// The stack pointer boundary is stored in a quickly-accessible location
// in the TCB. From that we can calculate the address of the stack segment
// structure it belongs to, and in that structure is a pointer to the task
// that owns it.
inline rust_task*
rust_task::get_task_from_tcb() {
uintptr_t sp_limit = get_sp_limit();
// FIXME (1226) - Because of a hack in upcall_call_shim_on_c_stack this
// value is sometimes inconveniently set to 0, so we can't use this
// method of retreiving the task pointer and need to fall back to TLS.
if (sp_limit == 0) {
return NULL;
}
uintptr_t seg_addr =
sp_limit - RED_ZONE_SIZE - LIMIT_OFFSET - sizeof(stk_seg);
stk_seg *stk = (stk_seg*) seg_addr;
// Make sure we've calculated the right address
::check_stack_canary(stk);
assert(stk->task != NULL && "task pointer not in stack structure");
return stk->task;
}
//
// Local Variables: