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Add necessary linker flags when -static-pie is enabled in BareMetal Toolchain #147589

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Add necessary linker flags when -static-pie is enabled in BareMetal Toolchain #147589

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2 changes: 2 additions & 0 deletions clang/include/clang/Driver/CommonArgs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,8 @@ const char *RelocationModelName(llvm::Reloc::Model Model);
std::tuple<llvm::Reloc::Model, unsigned, bool>
ParsePICArgs(const ToolChain &ToolChain, const llvm::opt::ArgList &Args);

bool getStaticPIE(const llvm::opt::ArgList &Args, const ToolChain &TC);

unsigned ParseFunctionAlignment(const ToolChain &TC,
const llvm::opt::ArgList &Args);

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19 changes: 15 additions & 4 deletions clang/lib/Driver/ToolChains/BareMetal.cpp
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Expand Up @@ -599,11 +599,18 @@ void baremetal::Linker::ConstructJob(Compilation &C, const JobAction &JA,
const Driver &D = getToolChain().getDriver();
const llvm::Triple::ArchType Arch = TC.getArch();
const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
const bool IsStaticPIE = getStaticPIE(Args, TC);

if (!D.SysRoot.empty())
CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));

CmdArgs.push_back("-Bstatic");
if (IsStaticPIE) {
CmdArgs.push_back("-pie");
CmdArgs.push_back("--no-dynamic-linker");
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This is already the default for LLD, is this needed for other linkers like GNU ld?

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@quic-garvgupt quic-garvgupt Jul 10, 2025 •
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This change is needed for both LLD and GNU LD. I dont see static -pie flags being passed by default for LLD if -static-pie is passed to clang driver. Moreover, without this change we get a unused argument warning as well.
Pls see below for verbose logs.

clang --target=aarch64-none-elf -fuse-ld=lld -static-pie empty.c -###

clang: warning: argument unused during compilation: '-static-pie' [-Wunused-command-line-argument]
...............................
ld.lld" "-Bstatic" "-m" "aarch64linux" "-EL" "crt0.o" "-L<path-to-bin>/../lib/clang-runtimes/aarch64-none-elf/lib" "-L<path>lib/clang/21/lib/aarch64-unknown-none-elf" "-L<path-to-bin>/../lib/clang-runtimes/aarch64-none-elf/lib" "/tmp/empty-09660d.o" "--start-group" "<path>/lib/clang/21/lib/aarch64-unknown-none-elf/libclang_rt.builtins.a" "-lc" "--end-group" "-o" "a.out"

Pls let me know if I missed something in your comment or interpreted it differently.

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I think @petrhosek was asking specifically about the "--no-dynamic-linker" flag.

I think for gnu ld it is necessary as it's possible to mix -static and -shared according to the manpage. I presume this ensures that you get an error in that case rather than a statically linked shared library.

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think @petrhosek was asking specifically about the "--no-dynamic-linker" flag.

Thanks for clarifying this.

I think for gnu ld it is necessary as it's possible to mix -static and -shared according to the manpage. I presume this ensures that you get an error in that case rather than a statically linked shared library.

Yes, if it’s the default behavior for LLD, then it would still be necessary for GNU LD. When both -static and -shared are used i.e., when creating a statically linked shared library, all definitions within the library are fully resolved at link time and pulled from static libraries. In such cases, there is no need for a dynamic linker.

CmdArgs.push_back("-z");
CmdArgs.push_back("text");
}

if (const char *LDMOption = getLDMOption(TC.getTriple(), Args)) {
CmdArgs.push_back("-m");
Expand Down Expand Up @@ -633,14 +640,18 @@ void baremetal::Linker::ConstructJob(Compilation &C, const JobAction &JA,

const char *CRTBegin, *CRTEnd;
if (NeedCRTs) {
if (!Args.hasArg(options::OPT_r))
CmdArgs.push_back(Args.MakeArgString(TC.GetFilePath("crt0.o")));
if (!Args.hasArg(options::OPT_r)) {
const char *crt = "crt0.o";
if (IsStaticPIE)
crt = "rcrt1.o";
CmdArgs.push_back(Args.MakeArgString(TC.GetFilePath(crt)));
}
if (TC.hasValidGCCInstallation() || detectGCCToolchainAdjacent(D)) {
auto RuntimeLib = TC.GetRuntimeLibType(Args);
switch (RuntimeLib) {
case (ToolChain::RLT_Libgcc): {
CRTBegin = "crtbegin.o";
CRTEnd = "crtend.o";
CRTBegin = IsStaticPIE ? "crtbeginS.o" : "crtbegin.o";
CRTEnd = IsStaticPIE ? "crtendS.o" : "crtend.o";
break;
}
case (ToolChain::RLT_CompilerRT): {
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12 changes: 12 additions & 0 deletions clang/lib/Driver/ToolChains/CommonArgs.cpp
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Expand Up @@ -2089,6 +2089,18 @@ tools::ParsePICArgs(const ToolChain &ToolChain, const ArgList &Args) {
return std::make_tuple(RelocM, 0U, false);
}

bool tools::getStaticPIE(const ArgList &Args, const ToolChain &TC) {
bool HasStaticPIE = Args.hasArg(options::OPT_static_pie);
if (HasStaticPIE && Args.hasArg(options::OPT_no_pie)) {
const Driver &D = TC.getDriver();
const llvm::opt::OptTable &Opts = D.getOpts();
StringRef StaticPIEName = Opts.getOptionName(options::OPT_static_pie);
StringRef NoPIEName = Opts.getOptionName(options::OPT_nopie);
D.Diag(diag::err_drv_cannot_mix_options) << StaticPIEName << NoPIEName;
}
return HasStaticPIE;
}

// `-falign-functions` indicates that the functions should be aligned to the
// backend's preferred alignment.
//
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12 changes: 0 additions & 12 deletions clang/lib/Driver/ToolChains/Gnu.cpp
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Expand Up @@ -219,18 +219,6 @@ void tools::gcc::Linker::RenderExtraToolArgs(const JobAction &JA,
// The types are (hopefully) good enough.
}

static bool getStaticPIE(const ArgList &Args, const ToolChain &TC) {
bool HasStaticPIE = Args.hasArg(options::OPT_static_pie);
if (HasStaticPIE && Args.hasArg(options::OPT_no_pie)) {
const Driver &D = TC.getDriver();
const llvm::opt::OptTable &Opts = D.getOpts();
StringRef StaticPIEName = Opts.getOptionName(options::OPT_static_pie);
StringRef NoPIEName = Opts.getOptionName(options::OPT_nopie);
D.Diag(diag::err_drv_cannot_mix_options) << StaticPIEName << NoPIEName;
}
return HasStaticPIE;
}

static bool getStatic(const ArgList &Args) {
return Args.hasArg(options::OPT_static) &&
!Args.hasArg(options::OPT_static_pie);
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12 changes: 12 additions & 0 deletions clang/test/Driver/aarch64-toolchain.c
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Expand Up @@ -157,3 +157,15 @@
// AARCH64-BAREMETAL-UNWINDLIB: "{{.*}}clang_rt.crtbegin.o"
// AARCH64-BAREMETAL-UNWINDLIB: "--start-group" "{{.*}}libclang_rt.builtins{{.*}}.a" "--as-needed" "-lunwind" "--no-as-needed" "-lc" "-lgloss" "--end-group"
// AARCH64-BAREMETAL-UNWINDLIB: "{{.*}}clang_rt.crtend.o"

// RUN: %clang -static-pie -### %s -fuse-ld= \
// RUN: --target=aarch64-none-elf --rtlib=libgcc --unwindlib=platform \
// RUN: --gcc-toolchain=%S/Inputs/basic_aarch64_gcc_tree \
// RUN: --sysroot=%S/Inputs/basic_arm_gcc_tree/aarch64-none-elf 2>&1 \
// RUN: | FileCheck -check-prefix=C-ARM-STATIC-PIE %s

// C-ARM-STATIC-PIE: "-Bstatic" "-pie" "--no-dynamic-linker" "-z" "text" "-m" "aarch64linux" "-EL"
// C-ARM-STATIC-PIE: "{{.*}}rcrt1.o"
// C-ARM-STATIC-PIE: "{{.*}}crtbeginS.o"
// C-ARM-STATIC-PIE: "--start-group" "-lgcc" "-lgcc_eh" "-lc" "-lgloss" "--end-group"
// C-ARM-STATIC-PIE: "{{.*}}crtendS.o"
12 changes: 12 additions & 0 deletions clang/test/Driver/arm-toolchain.c
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Expand Up @@ -158,3 +158,15 @@
// ARM-BAREMETAL-UNWINDLIB: "{{.*}}clang_rt.crtbegin.o"
// ARM-BAREMETAL-UNWINDLIB: "--start-group" "{{.*}}libclang_rt.builtins.a" "--as-needed" "-lunwind" "--no-as-needed" "-lc" "-lgloss" "--end-group"
// ARM-BAREMETAL-UNWINDLIB: "{{.*}}clang_rt.crtend.o"

// RUN: %clang -static-pie -### %s -fuse-ld= \
// RUN: --target=armv6m-none-eabi --rtlib=libgcc --unwindlib=platform \
// RUN: --gcc-toolchain=%S/Inputs/basic_arm_gcc_tree \
// RUN: --sysroot=%S/Inputs/basic_arm_gcc_tree/armv6m-none-eabi 2>&1 \
// RUN: | FileCheck -check-prefix=C-ARM-STATIC-PIE %s

// C-ARM-STATIC-PIE: "-Bstatic" "-pie" "--no-dynamic-linker" "-z" "text" "-m" "armelf_linux_eabi" "-EL"
// C-ARM-STATIC-PIE: "{{.*}}rcrt1.o"
// C-ARM-STATIC-PIE: "{{.*}}crtbeginS.o"
// C-ARM-STATIC-PIE: "--start-group" "-lgcc" "-lgcc_eh" "-lc" "-lgloss" "--end-group"
// C-ARM-STATIC-PIE: "{{.*}}crtendS.o"
13 changes: 13 additions & 0 deletions clang/test/Driver/riscv32-toolchain.c
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Expand Up @@ -247,6 +247,19 @@
// RUN: | FileCheck -check-prefix=CHECK-RV32-GNU-RELAX %s
// CHECK-RV32-GNU-RELAX-NOT: "--no-relax"

// Check that "-static -pie" is forwarded to linker when "-static-pie" is used
// RUN: %clang -static-pie -### %s -fuse-ld= \
// RUN: --target=riscv32-unknown-elf -rtlib=platform --unwindlib=platform \
// RUN: --gcc-toolchain=%S/Inputs/basic_riscv32_tree \
// RUN: --sysroot=%S/Inputs/basic_riscv32_tree/riscv32-unknown-elf 2>&1 \
// RUN: | FileCheck -check-prefix=C-RV32-STATIC-PIE %s

// C-RV32-STATIC-PIE: "-Bstatic" "-pie" "--no-dynamic-linker" "-z" "text" "-m" "elf32lriscv" "-X"
// C-RV32-STATIC-PIE: "{{.*}}rcrt1.o"
// C-RV32-STATIC-PIE: "{{.*}}crtbeginS.o"
// C-RV32-STATIC-PIE: "--start-group" "-lgcc" "-lc" "-lgloss" "--end-group"
// C-RV32-STATIC-PIE: "{{.*}}crtendS.o"

typedef __builtin_va_list va_list;
typedef __SIZE_TYPE__ size_t;
typedef __PTRDIFF_TYPE__ ptrdiff_t;
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13 changes: 13 additions & 0 deletions clang/test/Driver/riscv64-toolchain.c
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Expand Up @@ -203,6 +203,19 @@
// RUN: | FileCheck -check-prefix=CHECK-RV64-GNU-RELAX %s
// CHECK-RV64-GNU-RELAX-NOT: "--no-relax"

// Check that "-static -pie" is forwarded to linker when "-static-pie" is used
// RUN: %clang -static-pie -### %s -fuse-ld= \
// RUN: --target=riscv64-unknown-elf -rtlib=platform --unwindlib=platform \
// RUN: --gcc-toolchain=%S/Inputs/basic_riscv64_tree \
// RUN: --sysroot=%S/Inputs/basic_riscv64_tree/riscv64-unknown-elf 2>&1 \
// RUN: | FileCheck -check-prefix=C-RV64-STATIC-PIE %s

// C-RV64-STATIC-PIE: "-Bstatic" "-pie" "--no-dynamic-linker" "-z" "text" "-m" "elf64lriscv" "-X"
// C-RV64-STATIC-PIE: "{{.*}}rcrt1.o"
// C-RV64-STATIC-PIE: "{{.*}}crtbeginS.o"
// C-RV64-STATIC-PIE: "--start-group" "-lgcc" "-lc" "-lgloss" "--end-group"
// C-RV64-STATIC-PIE: "{{.*}}crtendS.o"

typedef __builtin_va_list va_list;
typedef __SIZE_TYPE__ size_t;
typedef __PTRDIFF_TYPE__ ptrdiff_t;
Expand Down