[compiler-rt] [profile] Perform pointer arithmetic in uintptr_t (PR #118944)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 6 01:25:26 PST 2024
https://github.com/nikic created https://github.com/llvm/llvm-project/pull/118944
Based on the feedback from #118782, this switches most of the pointer arithmetic in __llvm_profile_merge_from_buffer to work on uintptr_t instead of const char *, only casting back to a pointer when performing actual accesses.
This ensures that all the arithmetic is performed without any assumptions about pointer overflow.
>From 829a5464275c08c78c15e13c9c0ed095b5f50fc3 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Fri, 6 Dec 2024 10:22:52 +0100
Subject: [PATCH] [profile] Perform pointer arithmetic in uintptr_t
Based on the feedback from #118782, this switches most of the
pointer arithmetic in __llvm_profile_merge_from_buffer to work
on uintptr_t instead of const char *, only casting back to a
pointer when performing actual accesses.
This ensures that all the arithmetic is performed without any
assumptions about pointer overflow.
---
compiler-rt/lib/profile/InstrProfilingMerge.c | 67 ++++++++-----------
1 file changed, 29 insertions(+), 38 deletions(-)
diff --git a/compiler-rt/lib/profile/InstrProfilingMerge.c b/compiler-rt/lib/profile/InstrProfilingMerge.c
index a42fa74d1788eb..92721c4fd55ea2 100644
--- a/compiler-rt/lib/profile/InstrProfilingMerge.c
+++ b/compiler-rt/lib/profile/InstrProfilingMerge.c
@@ -127,12 +127,6 @@ getDistanceFromCounterToValueProf(const __llvm_profile_header *const Header) {
PaddingBytesAfterVNamesSize;
}
-// Add offset to pointer without assuming that the addition does not overflow.
-// This allows performing bounds checks by checking the result of the addition.
-static const char *ptr_add_with_overflow(const char *p, size_t offset) {
- return (const char *)((uintptr_t)p + offset);
-}
-
COMPILER_RT_VISIBILITY
int __llvm_profile_merge_from_buffer(const char *ProfileData,
uint64_t ProfileSize) {
@@ -143,28 +137,23 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
return 1;
}
- __llvm_profile_data *SrcDataStart, *SrcDataEnd, *SrcData, *DstData;
__llvm_profile_header *Header = (__llvm_profile_header *)ProfileData;
- char *SrcCountersStart, *DstCounter;
- const char *SrcCountersEnd, *SrcCounter;
- const char *SrcBitmapStart;
- const char *SrcNameStart;
- const char *SrcValueProfDataStart, *SrcValueProfData;
uintptr_t CountersDelta = Header->CountersDelta;
uintptr_t BitmapDelta = Header->BitmapDelta;
- SrcDataStart =
+ __llvm_profile_data *SrcDataStart =
(__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
Header->BinaryIdsSize);
- SrcDataEnd = SrcDataStart + Header->NumData;
- SrcCountersStart = (char *)SrcDataEnd;
- SrcCountersEnd = SrcCountersStart +
- Header->NumCounters * __llvm_profile_counter_entry_size();
- SrcBitmapStart = ptr_add_with_overflow(
- SrcCountersEnd,
- __llvm_profile_get_num_padding_bytes(SrcCountersEnd - SrcCountersStart));
- SrcNameStart = ptr_add_with_overflow(SrcBitmapStart, Header->NumBitmapBytes);
- SrcValueProfDataStart =
+ __llvm_profile_data *SrcDataEnd = SrcDataStart + Header->NumData;
+ uintptr_t SrcCountersStart = (uintptr_t)SrcDataEnd;
+ uintptr_t SrcCountersEnd =
+ SrcCountersStart +
+ Header->NumCounters * __llvm_profile_counter_entry_size();
+ uintptr_t SrcBitmapStart =
+ SrcCountersEnd +
+ __llvm_profile_get_num_padding_bytes(SrcCountersEnd - SrcCountersStart);
+ uintptr_t SrcNameStart = SrcBitmapStart + Header->NumBitmapBytes;
+ uintptr_t SrcValueProfDataStart =
SrcNameStart + getDistanceFromCounterToValueProf(Header);
if (SrcNameStart < SrcCountersStart || SrcNameStart < SrcBitmapStart)
return 1;
@@ -172,13 +161,13 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
// Merge counters by iterating the entire counter section when data section is
// empty due to correlation.
if (Header->NumData == 0) {
- for (SrcCounter = SrcCountersStart,
- DstCounter = __llvm_profile_begin_counters();
+ for (uintptr_t SrcCounter = SrcCountersStart,
+ DstCounter = (uintptr_t)__llvm_profile_begin_counters();
SrcCounter < SrcCountersEnd;) {
if (__llvm_profile_get_version() & VARIANT_MASK_BYTE_COVERAGE) {
- *DstCounter &= *SrcCounter;
+ *(char *)DstCounter &= *(const char *)SrcCounter;
} else {
- *(uint64_t *)DstCounter += *(uint64_t *)SrcCounter;
+ *(uint64_t *)DstCounter += *(const uint64_t *)SrcCounter;
}
SrcCounter += __llvm_profile_counter_entry_size();
DstCounter += __llvm_profile_counter_entry_size();
@@ -186,6 +175,8 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
return 0;
}
+ __llvm_profile_data *SrcData, *DstData;
+ uintptr_t SrcValueProfData;
for (SrcData = SrcDataStart,
DstData = (__llvm_profile_data *)__llvm_profile_begin_data(),
SrcValueProfData = SrcValueProfDataStart;
@@ -194,10 +185,10 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
// address of the data to the start address of the counter. On WIN64,
// CounterPtr is a truncated 32-bit value due to COFF limitation. Sign
// extend CounterPtr to get the original value.
- char *DstCounters =
- (char *)((uintptr_t)DstData + signextIfWin64(DstData->CounterPtr));
- char *DstBitmap =
- (char *)((uintptr_t)DstData + signextIfWin64(DstData->BitmapPtr));
+ uintptr_t DstCounters =
+ (uintptr_t)DstData + signextIfWin64(DstData->CounterPtr);
+ uintptr_t DstBitmap =
+ (uintptr_t)DstData + signextIfWin64(DstData->BitmapPtr);
unsigned NVK = 0;
// SrcData is a serialized representation of the memory image. We need to
@@ -207,8 +198,8 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
// CountersDelta computes the offset into the in-buffer counter section.
//
// On WIN64, CountersDelta is truncated as well, so no need for signext.
- const char *SrcCounters = ptr_add_with_overflow(
- SrcCountersStart, (uintptr_t)SrcData->CounterPtr - CountersDelta);
+ uintptr_t SrcCounters =
+ SrcCountersStart + ((uintptr_t)SrcData->CounterPtr - CountersDelta);
// CountersDelta needs to be decreased as we advance to the next data
// record.
CountersDelta -= sizeof(*SrcData);
@@ -221,14 +212,14 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
for (unsigned I = 0; I < NC; I++) {
if (__llvm_profile_get_version() & VARIANT_MASK_BYTE_COVERAGE) {
// A value of zero signifies the function is covered.
- DstCounters[I] &= SrcCounters[I];
+ ((char *)DstCounters)[I] &= ((const char *)SrcCounters)[I];
} else {
- ((uint64_t *)DstCounters)[I] += ((uint64_t *)SrcCounters)[I];
+ ((uint64_t *)DstCounters)[I] += ((const uint64_t *)SrcCounters)[I];
}
}
- const char *SrcBitmap = ptr_add_with_overflow(
- SrcBitmapStart, (uintptr_t)SrcData->BitmapPtr - BitmapDelta);
+ uintptr_t SrcBitmap =
+ SrcBitmapStart + ((uintptr_t)SrcData->BitmapPtr - BitmapDelta);
// BitmapDelta also needs to be decreased as we advance to the next data
// record.
BitmapDelta -= sizeof(*SrcData);
@@ -239,7 +230,7 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
return 1;
// Merge Src and Dst Bitmap bytes by simply ORing them together.
for (unsigned I = 0; I < NB; I++)
- DstBitmap[I] |= SrcBitmap[I];
+ ((char *)DstBitmap)[I] |= ((const char *)SrcBitmap)[I];
}
/* Now merge value profile data. */
@@ -252,7 +243,7 @@ int __llvm_profile_merge_from_buffer(const char *ProfileData,
if (!NVK)
continue;
- if (SrcValueProfData >= ProfileData + ProfileSize)
+ if (SrcValueProfData >= (uintptr_t)ProfileData + ProfileSize)
return 1;
VPMergeHook((ValueProfData *)SrcValueProfData, DstData);
SrcValueProfData =
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