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precise stack marking, fix some missed references, still imperfect

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* libguile/vm-engine.h (CHECK_STACK_LEAK, NULLSTACK): Add a new mode,
  VM_ENABLE_STACK_NULLING, that tries to ensure that all stack data past
  the top of the stack is NULL. This helps to verify the VM's
  consistency. If VM_ENABLE_STACK_NULLING is not defined, there is no
  overhead.
  (DROP, DROPN): Hook into NULLSTACK.
  (POP_LIST): Hoo, fix a good bug: if CONS triggered a GC, the elements
  of the list that had not yet been consed would not be marked, because
  the sp was already below them.
  (NEXT): Hook into CHECK_STACK_LEAK.
  (INIT_ARGS): Add a note that consing the rest arg can cause GC.
  (NEW_FRAME): Cons up the external data after initializing the frame, so
  that if GC is triggered, the precise marker sees a well-formed frame.

* libguile/vm-i-loader.c (load-program): In the four-integers case, use
  the POP macro so that we can hook into NULLSTACK (if necessary).

* libguile/vm-i-scheme.c (ARGS2, ARGS3): Hook into NULLSTACK.

* libguile/vm-i-system.c (halt): Null the nvalues. Rework some asserts
  into using ASSERT, and null the stack when we free the frame.
  (variable-set): Use DROPN instead of sp -= 2.
  (BR): Hook into NULLSTACK.
  (goto/args): Hook into NULLSTACK. In the non-self case, delay updating
  the frame until after INIT_ARGS so that GC sees a well-formed frame.
  Delay consing the externals until after the frame is set up, as in
  NEW_FRAME.
  (call/cc): Add some asserts.
  (return): Rework some asserts into ASSERT, and hook into NULLSTACK.
  (return/values): Hook into NULLSTACK, and use ASSERT.
  (return/values*) Use ASSERT.

* libguile/vm.c (VM_ENABLE_ASSERTIONS, VM_ENABLE_STACK_NULLING): These
  are the variables that control assertions and nulling. Perhaps we can
  do these per-engine when we start compiling the debug engine separate
  from a speedy engine.
  (vm_mark_stack): Add a precise stack marker. Yay!
  (vm_cont_mark): Mark the continuation stack precisely.
  (capture_vm_cont): Record the difference from the vp's stack_base too,
  so that we can translate the dynamic links when marking the
  continuation stack. Memset the stack to NULL if we are doing nulling.
  (reinstate_vm_cont): If we are nulling, null out the relevant part
  of the stack.
  (vm_reset_stack): When resetting sp due to a nonlocal exit, null out
  the stack too.
  (vm_mark): If we are nulling, assert that there are no extra values on
  the stack. Mark the stack precisely.
This commit is contained in:
Andy Wingo 2008-10-03 16:00:30 +02:00
parent edb1d1d78d
commit 11ea1aba9e
5 changed files with 157 additions and 61 deletions
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73
libguile/vm-i-system.c
View file

@ -58,6 +58,7 @@ VM_DEFINE_INSTRUCTION (halt, "halt", 0, 0, 0)
vp->time += scm_c_get_internal_run_time () - start_time;
HALT_HOOK ();
nvalues = SCM_I_INUM (*sp--);
NULLSTACK (1);
if (nvalues == 1)
POP (ret);
else
@ -69,17 +70,14 @@ VM_DEFINE_INSTRUCTION (halt, "halt", 0, 0, 0)
}
{
#ifdef THE_GOVERNMENT_IS_AFTER_ME
if (sp != stack_base)
abort ();
if (stack_base != SCM_FRAME_UPPER_ADDRESS (fp) - 1)
abort ();
#endif
ASSERT (sp == stack_base);
ASSERT (stack_base == SCM_FRAME_UPPER_ADDRESS (fp) - 1);
/* Restore registers */
sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
ip = NULL;
fp = SCM_FRAME_DYNAMIC_LINK (fp);
NULLSTACK (stack_base - sp);
}
SYNC_ALL ();
scm_dynwind_end ();
@ -366,7 +364,7 @@ VM_DEFINE_INSTRUCTION (external_set, "external-set", 1, 1, 0)
VM_DEFINE_INSTRUCTION (variable_set, "variable-set", 0, 1, 0)
{
VARIABLE_SET (sp[0], sp[-1]);
sp -= 2;
DROPN (2);
NEXT;
}
@ -435,6 +433,7 @@ VM_DEFINE_INSTRUCTION (late_variable_set, "late-variable-set", 1, 1, 0)
FETCH_OFFSET (offset); \
if (p) \
ip += offset; \
NULLSTACK (1); \
DROP (); \
NEXT; \
}
@ -621,6 +620,7 @@ VM_DEFINE_INSTRUCTION (goto_args, "goto/args", 1, -1, 1)
/* Drop the first argument and the program itself. */
sp -= 2;
NULLSTACK (bp->nargs + 1)
/* Call itself */
ip = bp->base;
@ -636,6 +636,9 @@ VM_DEFINE_INSTRUCTION (goto_args, "goto/args", 1, -1, 1)
SCM *data, *tail_args, *dl;
int i;
scm_byte_t *ra, *mvra;
#ifdef VM_ENABLE_STACK_NULLING
SCM *old_sp;
#endif
EXIT_HOOK ();
@ -646,11 +649,19 @@ VM_DEFINE_INSTRUCTION (goto_args, "goto/args", 1, -1, 1)
dl = SCM_FRAME_DYNAMIC_LINK (fp);
/* switch programs */
fp[-1] = program = x;
program = x;
CACHE_PROGRAM ();
INIT_ARGS ();
/* delay updating the frame so that if INIT_ARGS has to cons up a rest
arg, going into GC, the stack still makes sense */
fp[-1] = program;
nargs = bp->nargs;
#ifdef VM_ENABLE_STACK_NULLING
old_sp = sp;
CHECK_STACK_LEAK ();
#endif
/* new registers -- logically this would be better later, but let's make
sure we have space for the locals now */
data = SCM_FRAME_DATA_ADDRESS (fp);
@ -663,21 +674,26 @@ VM_DEFINE_INSTRUCTION (goto_args, "goto/args", 1, -1, 1)
for (i = 0; i < nargs; i++)
fp[i] = tail_args[i];
NULLSTACK (old_sp - sp);
/* init locals */
for (i = bp->nlocs; i; i--)
data[-i] = SCM_UNDEFINED;
/* and the external variables */
external = bp->external;
for (i = 0; i < bp->nexts; i++)
CONS (external, SCM_UNDEFINED, external);
/* Set frame data */
data[4] = (SCM)ra;
data[3] = (SCM)mvra;
data[2] = (SCM)dl;
data[1] = SCM_BOOL_F;
/* Postpone initializing external vars, because if the CONS causes a GC,
we want the stack marker to see the data array formatted as expected. */
data[0] = SCM_UNDEFINED;
external = bp->external;
for (i = 0; i < bp->nexts; i++)
CONS (external, SCM_UNDEFINED, external);
data[0] = external;
ENTER_HOOK ();
APPLY_HOOK ();
NEXT;
@ -887,6 +903,9 @@ VM_DEFINE_INSTRUCTION (call_cc, "call/cc", 0, 1, 1)
nargs = 1;
goto vm_call;
}
ASSERT (sp == vp->sp);
ASSERT (fp == vp->fp);
ASSERT (ip == vp->ip);
else if (SCM_VALUESP (cont))
{
/* multiple values returned to continuation */
@ -946,18 +965,20 @@ VM_DEFINE_INSTRUCTION (return, "return", 0, 0, 1)
data = SCM_FRAME_DATA_ADDRESS (fp);
POP (ret);
#ifdef THE_GOVERNMENT_IS_AFTER_ME
if (sp != stack_base)
abort ();
if (stack_base != data + 4)
abort ();
#endif
ASSERT (sp == stack_base);
ASSERT (stack_base == data + 4);
/* Restore registers */
sp = SCM_FRAME_LOWER_ADDRESS (fp);
ip = SCM_FRAME_BYTE_CAST (data[4]);
fp = SCM_FRAME_STACK_CAST (data[2]);
stack_base = SCM_FRAME_UPPER_ADDRESS (fp) - 1;
{
#ifdef VM_ENABLE_STACK_NULLING
int nullcount = stack_base - sp;
#endif
stack_base = SCM_FRAME_UPPER_ADDRESS (fp) - 1;
NULLSTACK (nullcount);
}
/* Set return value (sp is already pushed) */
*sp = ret;
@ -983,10 +1004,7 @@ VM_DEFINE_INSTRUCTION (return_values, "return/values", 1, -1, -1)
RETURN_HOOK ();
data = SCM_FRAME_DATA_ADDRESS (fp);
#ifdef THE_GOVERNMENT_IS_AFTER_ME
if (stack_base != data + 4)
abort ();
#endif
ASSERT (stack_base == data + 4);
/* data[3] is the mv return address */
if (nvalues != 1 && data[3])
@ -1003,6 +1021,7 @@ VM_DEFINE_INSTRUCTION (return_values, "return/values", 1, -1, -1)
*++sp = SCM_I_MAKINUM (nvalues);
/* Finally set new stack_base */
NULLSTACK (stack_base - sp + nvalues + 1);
stack_base = SCM_FRAME_UPPER_ADDRESS (fp) - 1;
}
else if (nvalues >= 1)
@ -1020,6 +1039,7 @@ VM_DEFINE_INSTRUCTION (return_values, "return/values", 1, -1, -1)
*++sp = stack_base[1];
/* Finally set new stack_base */
NULLSTACK (stack_base - sp);
stack_base = SCM_FRAME_UPPER_ADDRESS (fp) - 1;
}
else
@ -1038,10 +1058,7 @@ VM_DEFINE_INSTRUCTION (return_values_star, "return/values*", 1, -1, -1)
SCM l;
nvalues = FETCH ();
#ifdef THE_GOVERNMENT_IS_AFTER_ME
if (nvalues < 1)
abort ();
#endif
ASSERT (nvalues >= 1);
nvalues--;
POP (l);