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[BOLT][NFC] Add const qualifier to certain pointers to read-only objects #148543

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Merged
merged 2 commits into from
Jul 14, 2025
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[BOLT][NFC] Add const qualifier to certain pointers to read-only objects #148543

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0351b41
[BOLT][NFC] Add const qualifier to certain pointers to read-only objects
yozhu Jul 11, 2025
5402e06
Fix formatting error
yozhu Jul 13, 2025
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62 changes: 32 additions & 30 deletions bolt/runtime/instr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -568,13 +568,13 @@ struct FunctionDescription {
/// should be straightforward as most data is POD or an array of POD elements.
/// This metadata is used to reconstruct function CFGs.
struct ProfileWriterContext {
IndCallDescription *IndCallDescriptions;
IndCallTargetDescription *IndCallTargets;
uint8_t *FuncDescriptions;
char *Strings; // String table with function names used in this binary
const IndCallDescription *IndCallDescriptions;
const IndCallTargetDescription *IndCallTargets;
const uint8_t *FuncDescriptions;
const char *Strings; // String table with function names used in this binary
int FileDesc; // File descriptor for the file on disk backing this
// information in memory via mmap
void *MMapPtr; // The mmap ptr
const void *MMapPtr; // The mmap ptr
int MMapSize; // The mmap size

/// Hash table storing all possible call destinations to detect untracked
Expand Down Expand Up @@ -721,7 +721,7 @@ static char *getBinaryPath() {

ProfileWriterContext readDescriptions() {
ProfileWriterContext Result;
char *BinPath = getBinaryPath();
const char *BinPath = getBinaryPath();
assert(BinPath && BinPath[0] != '\0', "failed to find binary path");

uint64_t FD = __open(BinPath, O_RDONLY,
Expand All @@ -732,23 +732,24 @@ ProfileWriterContext readDescriptions() {

// mmap our binary to memory
uint64_t Size = __lseek(FD, 0, SEEK_END);
uint8_t *BinContents = reinterpret_cast<uint8_t *>(
const uint8_t *BinContents = reinterpret_cast<uint8_t *>(
__mmap(0, Size, PROT_READ, MAP_PRIVATE, FD, 0));
assert(BinContents != MAP_FAILED, "readDescriptions: Failed to mmap self!");
Result.MMapPtr = BinContents;
Result.MMapSize = Size;
Elf64_Ehdr *Hdr = reinterpret_cast<Elf64_Ehdr *>(BinContents);
Elf64_Shdr *Shdr = reinterpret_cast<Elf64_Shdr *>(BinContents + Hdr->e_shoff);
Elf64_Shdr *StringTblHeader = reinterpret_cast<Elf64_Shdr *>(
const Elf64_Ehdr *Hdr = reinterpret_cast<const Elf64_Ehdr *>(BinContents);
const Elf64_Shdr *Shdr =
reinterpret_cast<const Elf64_Shdr *>(BinContents + Hdr->e_shoff);
const Elf64_Shdr *StringTblHeader = reinterpret_cast<const Elf64_Shdr *>(
BinContents + Hdr->e_shoff + Hdr->e_shstrndx * Hdr->e_shentsize);

// Find .bolt.instr.tables with the data we need and set pointers to it
for (int I = 0; I < Hdr->e_shnum; ++I) {
char *SecName = reinterpret_cast<char *>(
const char *SecName = reinterpret_cast<const char *>(
BinContents + StringTblHeader->sh_offset + Shdr->sh_name);
if (compareStr(SecName, ".bolt.instr.tables", 64) != 0) {
Shdr = reinterpret_cast<Elf64_Shdr *>(BinContents + Hdr->e_shoff +
(I + 1) * Hdr->e_shentsize);
Shdr = reinterpret_cast<const Elf64_Shdr *>(BinContents + Hdr->e_shoff +
(I + 1) * Hdr->e_shentsize);
continue;
}
// Actual contents of the ELF note start after offset 20 decimal:
Expand All @@ -758,19 +759,19 @@ ProfileWriterContext readDescriptions() {
// Offset 12: Producer name (BOLT\0) (5 bytes + align to 4-byte boundary)
// Offset 20: Contents
uint32_t IndCallDescSize =
*reinterpret_cast<uint32_t *>(BinContents + Shdr->sh_offset + 20);
uint32_t IndCallTargetDescSize = *reinterpret_cast<uint32_t *>(
*reinterpret_cast<const uint32_t *>(BinContents + Shdr->sh_offset + 20);
uint32_t IndCallTargetDescSize = *reinterpret_cast<const uint32_t *>(
BinContents + Shdr->sh_offset + 24 + IndCallDescSize);
uint32_t FuncDescSize =
*reinterpret_cast<uint32_t *>(BinContents + Shdr->sh_offset + 28 +
IndCallDescSize + IndCallTargetDescSize);
Result.IndCallDescriptions = reinterpret_cast<IndCallDescription *>(
uint32_t FuncDescSize = *reinterpret_cast<const uint32_t *>(
BinContents + Shdr->sh_offset + 28 + IndCallDescSize +
IndCallTargetDescSize);
Result.IndCallDescriptions = reinterpret_cast<const IndCallDescription *>(
BinContents + Shdr->sh_offset + 24);
Result.IndCallTargets = reinterpret_cast<IndCallTargetDescription *>(
Result.IndCallTargets = reinterpret_cast<const IndCallTargetDescription *>(
BinContents + Shdr->sh_offset + 28 + IndCallDescSize);
Result.FuncDescriptions = BinContents + Shdr->sh_offset + 32 +
IndCallDescSize + IndCallTargetDescSize;
Result.Strings = reinterpret_cast<char *>(
Result.Strings = reinterpret_cast<const char *>(
BinContents + Shdr->sh_offset + 32 + IndCallDescSize +
IndCallTargetDescSize + FuncDescSize);
return Result;
Expand Down Expand Up @@ -814,13 +815,14 @@ void printStats(const ProfileWriterContext &Ctx) {
strCopy(StatPtr,
"\nBOLT INSTRUMENTATION RUNTIME STATISTICS\n\nIndCallDescSize: ");
StatPtr = intToStr(StatPtr,
Ctx.FuncDescriptions -
reinterpret_cast<uint8_t *>(Ctx.IndCallDescriptions),
Ctx.FuncDescriptions - reinterpret_cast<const uint8_t *>(
Ctx.IndCallDescriptions),
10);
StatPtr = strCopy(StatPtr, "\nFuncDescSize: ");
StatPtr = intToStr(
StatPtr,
reinterpret_cast<uint8_t *>(Ctx.Strings) - Ctx.FuncDescriptions, 10);
StatPtr = intToStr(StatPtr,
reinterpret_cast<const uint8_t *>(Ctx.Strings) -
Ctx.FuncDescriptions,
10);
StatPtr = strCopy(StatPtr, "\n__bolt_instr_num_ind_calls: ");
StatPtr = intToStr(StatPtr, __bolt_instr_num_ind_calls, 10);
StatPtr = strCopy(StatPtr, "\n__bolt_instr_num_funcs: ");
Expand Down Expand Up @@ -1549,7 +1551,7 @@ __bolt_instr_data_dump(int FD) {
Ctx.CallFlowTable->forEachElement(visitCallFlowEntry, FD, &Ctx);

__fsync(FD);
__munmap(Ctx.MMapPtr, Ctx.MMapSize);
__munmap((void *)Ctx.MMapPtr, Ctx.MMapSize);
__close(Ctx.FileDesc);
HashAlloc.destroy();
GlobalWriteProfileMutex->release();
Expand Down Expand Up @@ -1756,7 +1758,7 @@ extern "C" __attribute((naked)) void __bolt_instr_start()
"jal x1, __bolt_instr_setup\n"
RESTORE_ALL
"setup_symbol:\n"
"auipc x5, %%pcrel_hi(__bolt_start_trampoline)\n"
"auipc x5, %%pcrel_hi(__bolt_start_trampoline)\n"
"addi x5, x5, %%pcrel_lo(setup_symbol)\n"
"jr x5\n"
:::);
Expand Down Expand Up @@ -1788,8 +1790,8 @@ extern "C" void __bolt_instr_fini() {
__asm__ __volatile__(
SAVE_ALL
"fini_symbol:\n"
"auipc x5, %%pcrel_hi(__bolt_fini_trampoline)\n"
"addi x5, x5, %%pcrel_lo(fini_symbol)\n"
"auipc x5, %%pcrel_hi(__bolt_fini_trampoline)\n"
"addi x5, x5, %%pcrel_lo(fini_symbol)\n"
"jalr x1, 0(x5)\n"
RESTORE_ALL
:::);
Expand Down
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