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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 d53e313 commit 8233a8e

13 files changed

+205
-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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172+
void updateSize(uint64_t N) {
173+
if (N > Size)
174+
Size = N;
175+
}
176+
172177
void setIsMoveable(bool Flag) { IsMoveable = Flag; }
173178
void setSection(BinarySection &NewSection);
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void setOutputSection(BinarySection &NewSection) {

‎bolt/lib/Core/BinaryContext.cpp

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@@ -1073,6 +1073,7 @@ 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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9092
} // 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) {}
99+
100+
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 {
@@ -124,6 +154,8 @@ inline raw_ostream &operator<<(raw_ostream &OS, const ORCState &E) {
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namespace {
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126156
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.
@@ -225,6 +257,8 @@ 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.
229263
void processLKSections();
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@@ -290,6 +324,9 @@ class LinuxKernelRewriter final : public MetadataRewriter {
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: MetadataRewriter("linux-kernel-rewriter", BC) {}
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292326
Error preCFGInitializer() override {
327+
if (Error E = detectLinuxKernelVersion())
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return E;
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processLKSections();
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295332
if (Error E = processSMPLocks())
@@ -370,6 +407,28 @@ class LinuxKernelRewriter final : public MetadataRewriter {
370407
}
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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)) {
419+
const unsigned Major = std::stoi(Match[2].str());
420+
const unsigned Minor = std::stoi(Match[3].str());
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const unsigned Rev = Match[5].matched ? std::stoi(Match[5].str()) : 0;
422+
LinuxKernelVersion = LKVersion(Major, Minor, Rev);
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BC.outs() << "BOLT-INFO: Linux kernel version is " << Match[1].str()
424+
<< "\n";
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return Error::success();
426+
}
427+
}
428+
return createStringError(errc::executable_format_error,
429+
"Linux kernel version is unknown");
430+
}
431+
373432
void LinuxKernelRewriter::processLKSections() {
374433
processLKKSymtab();
375434
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
65+
.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
163+
.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
55+
.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.
4049
.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.
3948
.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-static-calls.s

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@@ -54,6 +54,15 @@ __start_static_call_sites:
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.type __stop_static_call_sites, %object
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__stop_static_call_sites:
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## Linux kernel version
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.rodata
59+
.align 16
60+
.globl linux_banner
61+
.type linux_banner, @object
62+
linux_banner:
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.string "Linux version 6.6.61\n"
64+
.size linux_banner, . - linux_banner
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## Fake Linux Kernel sections.
5867
.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-static-keys.s

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@@ -79,6 +79,21 @@ __start___jump_table:
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.type __stop___jump_table, %object
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__stop___jump_table:
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82+
## Staic keys (we just use the label ignoring the format of the keys).
83+
.data
84+
.align 8
85+
fake_static_key:
86+
.quad 0
87+
88+
## Linux kernel version
89+
.rodata
90+
.align 16
91+
.globl linux_banner
92+
.type linux_banner, @object
93+
linux_banner:
94+
.string "Linux version 6.6.61\n"
95+
.size linux_banner, . - linux_banner
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8297
## Fake Linux Kernel sections.
8398
.section __ksymtab,"a",@progbits
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.section __ksymtab_gpl,"a",@progbits

‎bolt/test/X86/linux-version.S

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@@ -0,0 +1,53 @@
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# REQUIRES: system-linux
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3+
## Check that BOLT correctly detects the Linux kernel version
4+
5+
# RUN: %clang -DA -target x86_64-unknown-unknown \
6+
# RUN: %cflags -nostdlib %s -o %t.exe \
7+
# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr
8+
# RUN: llvm-bolt %t.exe -o %t.out 2>&1 | FileCheck --check-prefix=CHECK-A %s
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10+
# RUN: %clang -DB -target x86_64-unknown-unknown \
11+
# RUN: %cflags -nostdlib %s -o %t.exe \
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# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr
13+
# RUN: llvm-bolt %t.exe -o %t.out 2>&1 | FileCheck --check-prefix=CHECK-B %s
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15+
# RUN: %clang -DC -target x86_64-unknown-unknown \
16+
# RUN: %cflags -nostdlib %s -o %t.exe \
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# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr
18+
# RUN: llvm-bolt %t.exe -o %t.out 2>&1 | FileCheck --check-prefix=CHECK-C %s
19+
20+
.text
21+
.globl foo
22+
.type foo, %function
23+
foo:
24+
ret
25+
.size foo, .-foo
26+
27+
## Linux kernel version
28+
.rodata
29+
.align 16
30+
.globl linux_banner
31+
.type linux_banner, @object
32+
linux_banner:
33+
34+
#ifdef A
35+
.string "Linux version 6.6.61\n"
36+
#endif
37+
# CHECK-A: BOLT-INFO: Linux kernel version is 6.6.61
38+
39+
#ifdef B
40+
.string "Linux version 6.6.50-rc4\n"
41+
#endif
42+
# CHECK-B: BOLT-INFO: Linux kernel version is 6.6.50
43+
44+
#ifdef C
45+
.string "Linux version 6.6\n"
46+
#endif
47+
# CHECK-C: BOLT-INFO: Linux kernel version is 6.6
48+
49+
.size linux_banner, . - linux_banner
50+
51+
## Fake Linux Kernel sections.
52+
.section __ksymtab,"a",@progbits
53+
.section __ksymtab_gpl,"a",@progbits

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