8000 gh-129223: Do not allow the compiler to optimise away symbols for debug sections by pablogsal · Pull Request #129225 · python/cpython · GitHub
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gh-129223: Do not allow the compiler to optimise away symbols for debug sections #129225

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Merged
merged 4 commits into from
Jan 24, 2025
Merged

gh-129223: Do not allow the compiler to optimise away symbols for debug sections #129225

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bd41fda
gh-129223: Do not allow the compiler to optimise away symbols for deb…
pablogsal Jan 23, 2025
3a87da4
Don't use __builtin_mul_overflow
ambv Jan 23, 2025
3350aa0
Fix type
pablogsal Jan 23, 2025
596a58f
Fix the other problem
pablogsal Jan 24, 2025
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21 changes: 11 additions & 10 deletions Include/internal/pycore_debug_offsets.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,31 +17,32 @@ extern "C" {

// Macros to burn global values in custom sections so out-of-process
// profilers can locate them easily.

#define GENERATE_DEBUG_SECTION(name, declaration) \
_GENERATE_DEBUG_SECTION_WINDOWS(name) \
_GENERATE_DEBUG_SECTION_APPLE(name) \
declaration \
_GENERATE_DEBUG_SECTION_LINUX(name)
#define GENERATE_DEBUG_SECTION(name, declaration) \
_GENERATE_DEBUG_SECTION_WINDOWS(name) \
_GENERATE_DEBUG_SECTION_APPLE(name) \
declaration \
_GENERATE_DEBUG_SECTION_LINUX(name)

#if defined(MS_WINDOWS)
#define _GENERATE_DEBUG_SECTION_WINDOWS(name) \
_Pragma(Py_STRINGIFY(section(Py_STRINGIFY(name), read, write))) \
__declspec(allocate(Py_STRINGIFY(name)))
_Pragma(Py_STRINGIFY(section(Py_STRINGIFY(name), read, write))) \
__declspec(allocate(Py_STRINGIFY(name)))
#else
#define _GENERATE_DEBUG_SECTION_WINDOWS(name)
#endif

#if defined(__APPLE__)
#define _GENERATE_DEBUG_SECTION_APPLE(name) \
__attribute__((section(SEG_DATA "," Py_STRINGIFY(name))))
__attribute__((section(SEG_DATA "," Py_STRINGIFY(name)))) \
__attribute__((used))
#else
#define _GENERATE_DEBUG_SECTION_APPLE(name)
#endif

#if defined(__linux__) && (defined(__GNUC__) || defined(__clang__))
#define _GENERATE_DEBUG_SECTION_LINUX(name) \
__attribute__((section("." Py_STRINGIFY(name))))
__attribute__((section("." Py_STRINGIFY(name)))) \
__attribute__((used))
#else
#define _GENERATE_DEBUG_SECTION_LINUX(name)
#endif
Expand Down
37 changes: 24 additions & 13 deletions Modules/_testexternalinspection.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,7 +414,11 @@ get_py_runtime(pid_t pid)
static uintptr_t
get_async_debug(pid_t pid)
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This change is to avoid returning NULL without an error set as things under search_map_for_section may return without setting an error.

{
return search_map_for_section(pid, "AsyncioDebug", "_asyncio.cpython");
uintptr_t result = search_map_for_section(pid, "AsyncioDebug", "_asyncio.cpython");
if (result == 0 && !PyErr_Occurred()) {
PyErr_SetString(PyExc_RuntimeError, "Cannot find AsyncioDebug section");
}
return result;
}


Expand Down Expand Up @@ -560,6 +564,16 @@ read_int(pid_t pid, uintptr_t address, int *result)
return 0;
}

static int
read_unsigned_long(pid_t pid, uintptr_t address, unsigned long *result)
{
int bytes_read = read_memory(pid, address, sizeof(unsigned long), result);
if (bytes_read < 0) {
return -1;
}
return 0;
}

static int
read_pyobj(pid_t pid, uintptr_t address, PyObject *ptr_addr)
{
Expand Down Expand Up @@ -627,7 +641,7 @@ read_py_long(pid_t pid, _Py_DebugOffsets* offsets, uintptr_t address)
return 0;
}

char *digits = (char *)PyMem_RawMalloc(size * sizeof(digit));
digit *digits = (digit *)PyMem_RawMalloc(size * sizeof(digit));
if (!digits) {
PyErr_NoMemory();
return -1;
Expand All @@ -645,16 +659,13 @@ read_py_long(pid_t pid, _Py_DebugOffsets* offsets, uintptr_t address)

long value = 0;

// In theory this can overflow, but because of llvm/llvm-project#16778
// we can't use __builtin_mul_overflow because it fails to link with
// __muloti4 on aarch64. In practice this is fine because all we're
// testing here are task numbers that would fit in a single byte.
for (ssize_t i = 0; i < size; ++i) {
long long factor;
if (__builtin_mul_overflow(digits[i], (1UL << (ssize_t)(shift * i)),
&factor)
) {
goto error;
}
if (__builtin_add_overflow(value, factor, &value)) {
goto error;
}
long long factor = digits[i] * (1UL << (ssize_t)(shift * i));
value += factor;
}
PyMem_RawFree(digits);
if (negative) {
Expand Down Expand Up @@ -693,8 +704,8 @@ parse_task_name(
return NULL;
}

int flags;
err = read_int(
unsigned long flags;
err = read_unsigned_long(
pid,
(uintptr_t)task_name_obj.ob_type + offsets->type_object.tp_flags,
&flags);
Expand Down
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