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vm: Fix stack-marking bug in multi-threaded programs.

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Fixes <https://bugs.gnu.org/28211>.

* libguile/vm-engine.c (call, call_label, handle_interrupts): Add
'new_fp' variable; set the dynamic link and return address of the frame
at NEW_FP before setting 'vp->fp'.  This fixes a bug whereby, in a
multi-threaded context, the stack-marking code could run after vp->fp
has been set but before its dynamic link has been set, leading the
stack-walking code in 'scm_i_vm_mark_stack' to exit early on.
This commit is contained in:
Ludovic Courtès 2018-06-29 22:28:48 +02:00 • committed by Andy Wingo
parent bab01b46ed
commit 8840ee5a3c
2 changed files with 28 additions and 20 deletions
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34
libguile/vm-engine.c
View file

@ -324,6 +324,7 @@ VM_NAME (scm_thread *thread)
/* Boot closure in r0, empty frame in r1/r2, proc in r3, values from r4. */
uint32_t nvals = FRAME_LOCALS_COUNT_FROM (4);
union scm_vm_stack_element *fp;
SCM ret;
if (nvals == 1)
@ -338,9 +339,10 @@ VM_NAME (scm_thread *thread)
SCM_SET_CELL_OBJECT (ret, n+1, FP_REF (4 + n));
}
VP->ip = SCM_FRAME_RETURN_ADDRESS (VP->fp);
VP->sp = SCM_FRAME_PREVIOUS_SP (VP->fp);
VP->fp = SCM_FRAME_DYNAMIC_LINK (VP->fp);
fp = VP->fp;
VP->fp = SCM_FRAME_DYNAMIC_LINK (fp);
VP->ip = SCM_FRAME_RETURN_ADDRESS (fp);
VP->sp = SCM_FRAME_PREVIOUS_SP (fp);
return ret;
}
@ -361,7 +363,7 @@ VM_NAME (scm_thread *thread)
VM_DEFINE_OP (1, call, "call", OP2 (X8_F24, X8_C24))
{
uint32_t proc, nlocals;
union scm_vm_stack_element *old_fp;
union scm_vm_stack_element *old_fp, *new_fp;
UNPACK_24 (op, proc);
UNPACK_24 (ip[1], nlocals);
@ -369,9 +371,10 @@ VM_NAME (scm_thread *thread)
PUSH_CONTINUATION_HOOK ();
old_fp = VP->fp;
VP->fp = SCM_FRAME_SLOT (old_fp, proc - 1);
SCM_FRAME_SET_DYNAMIC_LINK (VP->fp, old_fp);
SCM_FRAME_SET_RETURN_ADDRESS (VP->fp, ip + 2);
new_fp = SCM_FRAME_SLOT (old_fp, proc - 1);
SCM_FRAME_SET_DYNAMIC_LINK (new_fp, old_fp);
SCM_FRAME_SET_RETURN_ADDRESS (new_fp, ip + 2);
VP->fp = new_fp;
RESET_FRAME (nlocals);
@ -403,7 +406,7 @@ VM_NAME (scm_thread *thread)
{
uint32_t proc, nlocals;
int32_t label;
union scm_vm_stack_element *old_fp;
union scm_vm_stack_element *old_fp, *new_fp;
UNPACK_24 (op, proc);
UNPACK_24 (ip[1], nlocals);
@ -412,9 +415,10 @@ VM_NAME (scm_thread *thread)
PUSH_CONTINUATION_HOOK ();
old_fp = VP->fp;
VP->fp = SCM_FRAME_SLOT (old_fp, proc - 1);
SCM_FRAME_SET_DYNAMIC_LINK (VP->fp, old_fp);
SCM_FRAME_SET_RETURN_ADDRESS (VP->fp, ip + 3);
new_fp = SCM_FRAME_SLOT (old_fp, proc - 1);
SCM_FRAME_SET_DYNAMIC_LINK (new_fp, old_fp);
SCM_FRAME_SET_RETURN_ADDRESS (new_fp, ip + 3);
VP->fp = new_fp;
RESET_FRAME (nlocals);
@ -2387,9 +2391,11 @@ VM_NAME (scm_thread *thread)
*/
VM_DEFINE_OP (184, return_from_interrupt, "return-from-interrupt", OP1 (X32))
{
VP->sp = sp = SCM_FRAME_PREVIOUS_SP (VP->fp);
ip = SCM_FRAME_RETURN_ADDRESS (VP->fp);
VP->fp = SCM_FRAME_DYNAMIC_LINK (VP->fp);
union scm_vm_stack_element *fp = VP->fp;
ip = SCM_FRAME_RETURN_ADDRESS (fp);
VP->fp = SCM_FRAME_DYNAMIC_LINK (fp);
VP->sp = sp = SCM_FRAME_PREVIOUS_SP (fp);
NEXT (0);
}

14
libguile/vm.c
View file

@ -1013,7 +1013,7 @@ cons_rest (scm_thread *thread, uint32_t base)
static void
push_interrupt_frame (scm_thread *thread)
{
union scm_vm_stack_element *old_fp;
union scm_vm_stack_element *old_fp, *new_fp;
size_t old_frame_size = frame_locals_count (thread);
SCM proc = scm_i_async_pop (thread);
@ -1024,13 +1024,14 @@ push_interrupt_frame (scm_thread *thread)
alloc_frame (thread, old_frame_size + 3);
old_fp = thread->vm.fp;
thread->vm.fp = SCM_FRAME_SLOT (old_fp, old_frame_size + 1);
SCM_FRAME_SET_DYNAMIC_LINK (thread->vm.fp, old_fp);
new_fp = SCM_FRAME_SLOT (old_fp, old_frame_size + 1);
SCM_FRAME_SET_DYNAMIC_LINK (new_fp, old_fp);
/* Arrange to return to the same handle-interrupts opcode to handle
any additional interrupts. */
SCM_FRAME_SET_RETURN_ADDRESS (thread->vm.fp, thread->vm.ip);
SCM_FRAME_SET_RETURN_ADDRESS (new_fp, thread->vm.ip);
SCM_FRAME_LOCAL (new_fp, 0) = proc;
SCM_FRAME_LOCAL (thread->vm.fp, 0) = proc;
thread->vm.fp = new_fp;
}
struct return_to_continuation_data
@ -1402,7 +1403,6 @@ scm_call_n (SCM proc, SCM *argv, size_t nargs)
SCM_FRAME_LOCAL (return_fp, 0) = vm_boot_continuation;
vp->ip = (uint32_t *) vm_boot_continuation_code;
vp->fp = call_fp;
SCM_FRAME_SET_RETURN_ADDRESS (call_fp, vp->ip);
SCM_FRAME_SET_DYNAMIC_LINK (call_fp, return_fp);
@ -1410,6 +1410,8 @@ scm_call_n (SCM proc, SCM *argv, size_t nargs)
for (i = 0; i < nargs; i++)
SCM_FRAME_LOCAL (call_fp, i + 1) = argv[i];
vp->fp = call_fp;
{
jmp_buf registers;
int resume;