On Monday 09 July 2007 02:49:03 Nuno 'smash' Carvalho wrote:
> I saw your sentinel patch but didn't apply it yet.
> Is this related to you sentnel patch? I can re-test this after appling it.
Here's a better version. I suspect it's not very portable. It probably needs
to fix up page alignment, and it's definitely not quite POSIX kosher.
It does create some interesting aborts though.
-- c
=== include/parrot/pobj.h
==================================================================
--- include/parrot/pobj.h (revision 4598)
+++ include/parrot/pobj.h (local)
@@ -47,6 +47,7 @@
/* plain Buffer is the smallest Parrot Obj */
typedef struct Buffer {
+ char sentinel[4200];
pobj_t obj;
} Buffer;
@@ -124,6 +125,7 @@
} parrot_string_representation_t;
struct parrot_string_t {
+ char sentinel[4200];
pobj_t obj;
UINTVAL bufused;
char *strstart;
@@ -134,11 +136,17 @@
UINTVAL hashval; /* cached hash value computation; not yet used */
};
+static void make_sentinel(PObj *o)
+{
+ /* Make the memory unwritable. */
+ mprotect(o->sentinel, 4096, PROT_READ);
+}
/* put data into the PMC_EXT structure */
#define PMC_DATA_IN_EXT 1
struct PMC {
+ char sentinel[4200];
pobj_t obj;
VTABLE *vtable;
PMC *real_self;
=== include/parrot/stacks.h
==================================================================
--- include/parrot/stacks.h (revision 4598)
+++ include/parrot/stacks.h (local)
@@ -25,6 +25,7 @@
} Stack_Entry_t;
typedef struct Stack_Chunk {
+ char sentinel[4200];
pobj_t obj;
int size;
const char * name;
=== src/gc/smallobject.c
==================================================================
--- src/gc/smallobject.c (revision 4598)
+++ src/gc/smallobject.c (local)
@@ -151,6 +151,7 @@
gc_ms_add_free_object(SHIM_INTERP, Small_Object_Pool *pool /*NN*/,
void *to_add /*NN*/)
{
+ mprotect(((PObj *)to_add)->sentinel, 4, PROT_WRITE);
*(void **)to_add = pool->free_list;
pool->free_list = to_add;
}
=== src/headers.c
==================================================================
--- src/headers.c (revision 4598)
+++ src/headers.c (local)
@@ -89,6 +89,8 @@
if (pool->object_size - GC_HEADER_SIZE > sizeof (PObj))
memset(buffer + 1, 0,
pool->object_size - sizeof (PObj) - GC_HEADER_SIZE);
+
+ make_sentinel((PObj *)buffer);
return buffer;
}
@@ -247,6 +249,7 @@
? interp->arena_base->constant_pmc_pool
: interp->arena_base->pmc_pool;
PMC * const pmc = (PMC *)pool->get_free_object(interp, pool);
+ make_sentinel((PObj *)pmc);
/* clear flags, set is_PMC_FLAG */
if (flags & PObj_is_PMC_EXT_FLAG) {
@@ -356,6 +359,7 @@
flags | PObj_is_string_FLAG | PObj_is_COWable_FLAG | PObj_live_FLAG;
string->strstart = NULL;
+ make_sentinel((PObj *)string);
return string;
}
=== src/pmc.c
==================================================================
--- src/pmc.c (revision 4598)
+++ src/pmc.c (local)
@@ -199,6 +199,7 @@
pmc->real_self = pmc;
VTABLE_set_pointer(interp, pmc, pmc);
}
+ make_sentinel((PObj *)pmc);
return pmc;
}
if (vtable->flags & VTABLE_IS_CONST_PMC_FLAG) {
@@ -245,6 +246,7 @@
fprintf(stderr, "\t=> new %p type %d\n", pmc, (int)base_type);
}
#endif
+ make_sentinel((PObj *)pmc);
return pmc;
}
=== src/stack_common.c
==================================================================
--- src/stack_common.c (revision 4598)
+++ src/stack_common.c (local)
@@ -79,7 +79,8 @@
Stack_Chunk_t * const new_chunk = (Stack_Chunk_t *)pool->get_free_object(interp, pool);
PObj_bufstart(new_chunk) = NULL;
- PObj_buflen(new_chunk) = 0;
+ PObj_buflen(new_chunk) = 0;
+ make_sentinel((PObj *)new_chunk);
new_chunk->size = chunk->size;
new_chunk->name = chunk->name;
=== src/string.c
==================================================================
--- src/string.c (revision 4598)
+++ src/string.c (local)
@@ -91,6 +91,7 @@
* also be sure not to allocate from the constant pool
*/
PObj_flags_CLEARALL(&for_alloc);
+ make_sentinel((PObj *)&for_alloc);
Parrot_allocate_string(interp, &for_alloc, PObj_buflen(s));
/* now copy memory over */
@@ -130,8 +131,10 @@
if (PObj_constant_TEST(s)) {
d = new_string_header(interp, PObj_get_FLAGS(s) & ~PObj_constant_FLAG);
+ mprotect(d->sentinel, 4096, PROT_WRITE);
PObj_COW_SET(s);
STRUCT_COPY(d,s);
+ mprotect(d->sentinel, 4096, PROT_READ);
/* we can't move the memory, because constants aren't
* scanned in compact_pool, therefore the other end
* would point to garbage.
@@ -142,7 +145,9 @@
else {
d = new_string_header(interp, PObj_get_FLAGS(s));
PObj_COW_SET(s);
+ mprotect(d->sentinel, 4096, PROT_WRITE);
STRUCT_COPY(d,s);
+ mprotect(d->sentinel, 4096, PROT_READ);
PObj_sysmem_CLEAR(d);
#if 0
/* XXX FIXME hack to avoid cross-interpreter issue until it
