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[BOLT] Enable re-writing of Linux kernel binary #80228

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merged 1 commit into from
Feb 1, 2024
Merged

[BOLT] Enable re-writing of Linux kernel binary #80228

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21 changes: 14 additions & 7 deletions bolt/lib/Rewrite/RewriteInstance.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -757,12 +757,11 @@ Error RewriteInstance::run() {
if (opts::Instrument && !BC->IsStaticExecutable)
updateRtFiniReloc();

if (BC->IsLinuxKernel) {
errs() << "BOLT-WARNING: not writing the output file for Linux Kernel\n";
return Error::success();
} else if (opts::OutputFilename == "/dev/null") {
if (opts::OutputFilename == "/dev/null") {
outs() << "BOLT-INFO: skipping writing final binary to disk\n";
return Error::success();
} else if (BC->IsLinuxKernel) {
errs() << "BOLT-WARNING: Linux kernel support is experimental\n";
}

// Rewrite allocatable contents and copy non-allocatable parts with mods.
Expand Down Expand Up @@ -1860,6 +1859,11 @@ Error RewriteInstance::readSpecialSections() {
BC->HasRelocations =
HasTextRelocations && (opts::RelocationMode != cl::BOU_FALSE);

if (BC->IsLinuxKernel && BC->HasRelocations) {
outs() << "BOLT-INFO: disabling relocation mode for Linux kernel\n";
BC->HasRelocations = false;
}

BC->IsStripped = !HasSymbolTable;

if (BC->IsStripped && !opts::AllowStripped) {
Expand Down Expand Up @@ -4369,8 +4373,10 @@ void RewriteInstance::patchELFSectionHeaderTable(ELFObjectFile<ELFT> *File) {
assert((NewEhdr.e_entry || !Obj.getHeader().e_entry) &&
"cannot find new address for entry point");
}
NewEhdr.e_phoff = PHDRTableOffset;
NewEhdr.e_phnum = Phnum;
if (PHDRTableOffset) {
NewEhdr.e_phoff = PHDRTableOffset;
NewEhdr.e_phnum = Phnum;
}
NewEhdr.e_shoff = SHTOffset;
NewEhdr.e_shnum = OutputSections.size();
NewEhdr.e_shstrndx = NewSectionIndex[NewEhdr.e_shstrndx];
Expand Down Expand Up @@ -5505,7 +5511,8 @@ void RewriteInstance::rewriteFile() {
addBATSection();

// Patch program header table.
patchELFPHDRTable();
if (!BC->IsLinuxKernel)
patchELFPHDRTable();

// Finalize memory image of section string table.
finalizeSectionStringTable();
Expand Down
2 changes: 2 additions & 0 deletions bolt/test/X86/linux-orc.s
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Expand Up @@ -52,6 +52,8 @@ bar:
.L4:
.size bar, .-bar

# CHECK: BOLT-WARNING: Linux kernel support is experimental

.section .orc_unwind,"a",@progbits
.align 4
.section .orc_unwind_ip,"a",@progbits
Expand Down
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