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GH-116017: Put JIT code and data on the same page (GH-116845)

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Brandt Bucher 2024-03-19 08:47:28 -07:00 • committed by GitHub
parent f55e1880c1
commit 2c82592ab4
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3 changed files with 27 additions and 34 deletions
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52
Python/jit.c
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@ -112,26 +112,6 @@ mark_executable(unsigned char *memory, size_t size)
return 0;
}
static int
mark_readable(unsigned char *memory, size_t size)
{
if (size == 0) {
return 0;
}
assert(size % get_page_size() == 0);
#ifdef MS_WINDOWS
DWORD old;
int failed = !VirtualProtect(memory, size, PAGE_READONLY, &old);
#else
int failed = mprotect(memory, size, PROT_READ);
#endif
if (failed) {
jit_error("unable to protect readable memory");
return -1;
}
return 0;
}
// JIT compiler stuff: /////////////////////////////////////////////////////////
// Warning! AArch64 requires you to get your hands dirty. These are your gloves:
@ -409,12 +389,14 @@ _PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction *trace, size
code_size += group->code.body_size;
data_size += group->data.body_size;
}
// Round up to the nearest page (code and data need separate pages):
code_size += stencil_groups[_FATAL_ERROR].code.body_size;
data_size += stencil_groups[_FATAL_ERROR].data.body_size;
// Round up to the nearest page:
size_t page_size = get_page_size();
assert((page_size & (page_size - 1)) == 0);
code_size += page_size - (code_size & (page_size - 1));
data_size += page_size - (data_size & (page_size - 1));
unsigned char *memory = jit_alloc(code_size + data_size);
size_t padding = page_size - ((code_size + data_size) & (page_size - 1));
size_t total_size = code_size + data_size + padding;
unsigned char *memory = jit_alloc(total_size);
if (memory == NULL) {
return -1;
}
@ -444,14 +426,26 @@ _PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction *trace, size
code += group->code.body_size;
data += group->data.body_size;
}
if (mark_executable(memory, code_size) ||
mark_readable(memory + code_size, data_size))
{
jit_free(memory, code_size + data_size);
// Protect against accidental buffer overrun into data:
const StencilGroup *group = &stencil_groups[_FATAL_ERROR];
uint64_t patches[] = GET_PATCHES();
patches[HoleValue_CODE] = (uint64_t)code;
patches[HoleValue_CONTINUE] = (uint64_t)code;
patches[HoleValue_DATA] = (uint64_t)data;
patches[HoleValue_EXECUTOR] = (uint64_t)executor;
patches[HoleValue_TOP] = (uint64_t)code;
patches[HoleValue_ZERO] = 0;
emit(group, patches);
code += group->code.body_size;
data += group->data.body_size;
assert(code == memory + code_size);
assert(data == memory + code_size + data_size);
if (mark_executable(memory, total_size)) {
jit_free(memory, total_size);
return -1;
}
executor->jit_code = memory;
executor->jit_size = code_size + data_size;
executor->jit_size = total_size;
return 0;
}