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Fix ogg_sync_pageout hook infinite recursion after 2df07b59 #3707

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Fix ogg_sync_pageout hook infinite recursion after 2df07b59 #3707

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2 changes: 2 additions & 0 deletions src/include/alternate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@ void* getAlternate(void* addr);
void addAlternate(void* addr, void* alt);
void addCheckAlternate(void* addr, void* alt);
void cleanAlternate(void);
void suppressAlternate(void* addr);
void unsuppressAlternate(void* addr);
#ifdef HAVE_ALTJUMP
uintptr_t getAlternateJump(void* addr, int is32bits);
#endif
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6 changes: 5 additions & 1 deletion src/mallochook.c
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Original file line number Diff line number Diff line change
Expand Up @@ -881,8 +881,12 @@ static void* ogg_page_body_copy = NULL;

static int my_ogg_sync_pageout_32(void* oy, void* og)
{
// Call the original emulated ogg_sync_pageout
// Suppress the alternate for the duration of the call to avoid
// infinite recursion: RunFunctionFmt -> EmuRun -> getAlternate
// would redirect back to this hook without suppression.
suppressAlternate((void*)real_ogg_sync_pageout_32);
int ret = (int)RunFunctionFmt(real_ogg_sync_pageout_32, "pp", oy, og);
unsuppressAlternate((void*)real_ogg_sync_pageout_32);

if(ret > 0 && og) {
// ogg_sync_pageout succeeded — og now has pointers into oy->data
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23 changes: 22 additions & 1 deletion src/tools/alternate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,9 +20,17 @@ typedef struct {
KHASH_MAP_INIT_INT64(alternate, my_alternate_t)
static kh_alternate_t *my_alternates = NULL;

// Per-address suppression: when set, getAlternate/hasAlternate/getAlternateJump
// will return "no alternate" for this specific address. Used by hooks that need
// to call through to the original emulated function via RunFunctionFmt without
// triggering infinite recursion (EmuRun applies getAlternate every iteration).
static uintptr_t alternate_suppress = 0;

int hasAlternate(void* addr) {
if(!my_alternates)
return 0;
if((uintptr_t)addr == alternate_suppress)
return 0;
khint_t k = kh_get(alternate, my_alternates, (uintptr_t)addr);
if(k==kh_end(my_alternates))
return 0;
Expand All @@ -32,6 +40,8 @@ int hasAlternate(void* addr) {
void* getAlternate(void* addr) {
if(!my_alternates)
return addr;
if((uintptr_t)addr == alternate_suppress)
return addr;
khint_t k = kh_get(alternate, my_alternates, (uintptr_t)addr);
if(k!=kh_end(my_alternates))
return kh_value(my_alternates, k).addr;
Expand All @@ -53,6 +63,15 @@ void addAlternate(void* addr, void* alt) {
#endif
}

void suppressAlternate(void* addr) {
alternate_suppress = (uintptr_t)addr;
}

void unsuppressAlternate(void* addr) {
(void)addr;
alternate_suppress = 0;
}

void addCheckAlternate(void* addr, void* alt) {
if(!hasAlternate(addr))
addAlternate(addr, alt);
Expand All @@ -70,6 +89,8 @@ void cleanAlternate() {
uintptr_t getAlternateJump(void* addr, int is32bits) {
if(!my_alternates)
return 0;
if((uintptr_t)addr == alternate_suppress)
return 0;
khint_t k = kh_get(alternate, my_alternates, (uintptr_t)addr);
if(k!=kh_end(my_alternates)) {
uintptr_t ret = kh_value(my_alternates, k).jump;
Expand All @@ -78,4 +99,4 @@ uintptr_t getAlternateJump(void* addr, int is32bits) {
}
return 0;
}
#endif
#endif
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