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Fix ARM hook into JSGlobalContextCreateInGroup

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We were loading into the program counter, which is not good in THUMB mode, so we now instead load into R3, since it's a temp register not used by this function (it only takes two arguments). Also, when building this module in THUMB mode itself, we needed to clear the ARM instruction cache, which wasn't needed when switching from THUMB to ARM mode.
This commit is contained in:
Scott Kyle 2016-03-13 22:03:40 -07:00 committed by Ari Lazier
parent b053947353
commit 7feadb27b2
1 changed files with 16 additions and 2 deletions
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18
src/android/jsc_override.cpp
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@ -88,8 +88,8 @@ static void swap_function()
#if __arm__
if (orig_thumb) {
// LDR PC, [PC, #0]; BX PC;
memcpy(orig_func, "\x00\x4f\x38\x47", 4);
// LDR R3, [PC, #0]; BX R3;
memcpy(orig_func, "\x00\x4b\x18\x47", 4);
memcpy(orig_func + 4, &new_func, 4);
} else {
// LDR PC, [PC, #0];
@ -107,6 +107,20 @@ static void swap_function()
s_swapped = !s_swapped;
#if __arm__
// Clear ARM instruction cache.
{
register unsigned long begin __asm("a1") = (unsigned long)orig_func;
register unsigned long end __asm("a2") = (unsigned long)code_end;
register unsigned long flag __asm("a3") = 0;
register unsigned long scno __asm("r7") = 0xf0002;
__asm __volatile (
"swi 0 @ sys_cacheflush"
: "=r" (begin)
: "0" (begin), "r" (end), "r" (flag), "r" (scno)
);
};
#endif
// Return this region to no longer being writable.
mprotect((void*)page_start, code_end - page_start, PROT_READ | PROT_EXEC);
}