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[BOLT] Detect Linux kernel version if the binary is a Linux kernel (#119088)
This makes it easier to handle differences (e.g. of exception table entry size) between versions of Linux kernel
1 parent 8906b7b commit 6e8a1a4

13 files changed

+199
-0
lines changed

‎bolt/include/bolt/Core/BinaryData.h‎

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@@ -169,6 +169,11 @@ class BinaryData {
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return Parent && (Parent == BD || Parent->isAncestorOf(BD));
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}
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void updateSize(uint64_t N) {
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if (N > Size)
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Size = N;
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}
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void setIsMoveable(bool Flag) { IsMoveable = Flag; }
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void setSection(BinarySection &NewSection);
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void setOutputSection(BinarySection &NewSection) {

‎bolt/lib/Core/BinaryContext.cpp‎

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@@ -1076,6 +1076,7 @@ MCSymbol *BinaryContext::registerNameAtAddress(StringRef Name, uint64_t Address,
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BD = GAI->second;
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if (!BD->hasName(Name)) {
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GlobalSymbols[Name] = BD;
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BD->updateSize(Size);
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BD->Symbols.push_back(Symbol);
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}
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}

‎bolt/lib/Rewrite/LinuxKernelRewriter.cpp‎

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@@ -21,6 +21,8 @@
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Errc.h"
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#include "llvm/Support/ErrorOr.h"
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#include <regex>
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#define DEBUG_TYPE "bolt-linux"
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@@ -89,6 +91,34 @@ static cl::opt<bool>
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} // namespace opts
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/// Linux kernel version
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struct LKVersion {
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LKVersion() {}
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LKVersion(unsigned Major, unsigned Minor, unsigned Rev)
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: Major(Major), Minor(Minor), Rev(Rev) {}
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bool operator<(const LKVersion &Other) const {
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return std::make_tuple(Major, Minor, Rev) <
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std::make_tuple(Other.Major, Other.Minor, Other.Rev);
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}
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bool operator>(const LKVersion &Other) const { return Other < *this; }
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bool operator<=(const LKVersion &Other) const { return !(*this > Other); }
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bool operator>=(const LKVersion &Other) const { return !(*this < Other); }
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bool operator==(const LKVersion &Other) const {
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return Major == Other.Major && Minor == Other.Minor && Rev == Other.Rev;
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}
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bool operator!=(const LKVersion &Other) const { return !(*this == Other); }
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unsigned Major{0};
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unsigned Minor{0};
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unsigned Rev{0};
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};
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/// Linux Kernel supports stack unwinding using ORC (oops rewind capability).
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/// ORC state at every IP can be described by the following data structure.
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struct ORCState {
@@ -148,6 +178,8 @@ class AddressExtractor : public DataExtractor {
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};
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class LinuxKernelRewriter final : public MetadataRewriter {
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LKVersion LinuxKernelVersion;
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/// Information required for updating metadata referencing an instruction.
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struct InstructionFixup {
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BinarySection &Section; // Section referencing the instruction.
@@ -249,6 +281,8 @@ class LinuxKernelRewriter final : public MetadataRewriter {
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ErrorOr<BinarySection &> PCIFixupSection = std::errc::bad_address;
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static constexpr size_t PCI_FIXUP_ENTRY_SIZE = 16;
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Error detectLinuxKernelVersion();
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/// Process linux kernel special sections and their relocations.
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void processLKSections();
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@@ -314,6 +348,9 @@ class LinuxKernelRewriter final : public MetadataRewriter {
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: MetadataRewriter("linux-kernel-rewriter", BC) {}
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Error preCFGInitializer() override {
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if (Error E = detectLinuxKernelVersion())
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return E;
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processLKSections();
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if (Error E = processSMPLocks())
@@ -394,6 +431,28 @@ class LinuxKernelRewriter final : public MetadataRewriter {
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}
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};
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Error LinuxKernelRewriter::detectLinuxKernelVersion() {
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if (BinaryData *BD = BC.getBinaryDataByName("linux_banner")) {
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const BinarySection &Section = BD->getSection();
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const std::string S =
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Section.getContents().substr(BD->getOffset(), BD->getSize()).str();
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const std::regex Re(R"---(Linux version ((\d+)\.(\d+)(\.(\d+))?))---");
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std::smatch Match;
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if (std::regex_search(S, Match, Re)) {
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const unsigned Major = std::stoi(Match[2].str());
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const unsigned Minor = std::stoi(Match[3].str());
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const unsigned Rev = Match[5].matched ? std::stoi(Match[5].str()) : 0;
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LinuxKernelVersion = LKVersion(Major, Minor, Rev);
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BC.outs() << "BOLT-INFO: Linux kernel version is " << Match[1].str()
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<< "\n";
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return Error::success();
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}
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}
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return createStringError(errc::executable_format_error,
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"Linux kernel version is unknown");
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}
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void LinuxKernelRewriter::processLKSections() {
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processLKKSymtab();
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processLKKSymtab(true);

‎bolt/test/X86/linux-alt-instruction.s‎

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@@ -142,6 +142,15 @@ _start:
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.section .orc_unwind_ip
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.long .L0 + 2 - .
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-bug-table.s‎

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@@ -56,6 +56,15 @@ _start:
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.long .L1 - . # instruction
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.org 2b + 12
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-exceptions.s‎

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@@ -59,6 +59,15 @@ foo:
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.long .LF0 - . # fixup
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.long 0 # data
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-orc.s‎

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@@ -157,6 +157,15 @@ bar:
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.section .orc_unwind_ip
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.long .L4 - .
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-parainstructions.s‎

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@@ -49,6 +49,15 @@ _start:
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.byte 1 # type
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.byte 7 # length
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-pci-fixup.s‎

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@@ -36,6 +36,15 @@ _start:
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.long 0x0 # class shift
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.long .L0 - . # fixup
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-smp-locks.s‎

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@@ -35,6 +35,15 @@ _start:
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.long .L0 - .
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.long .L1 - .
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## Linux kernel version
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.rodata
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.align 16
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.globl linux_banner
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.type linux_banner, @object
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linux_banner:
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.string "Linux version 6.6.61\n"
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.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
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.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

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