[lld] [lld][ELF] Introduce an option to keep data section prefix. (PR #148985)
Mingming Liu via llvm-commits
llvm-commits at lists.llvm.org
Sun Jul 20 22:54:55 PDT 2025
https://github.com/mingmingl-llvm updated https://github.com/llvm/llvm-project/pull/148985
>From 24c1c62b584fb42fcd91b9343bbe61e521038dd0 Mon Sep 17 00:00:00 2001
From: mingmingl <mingmingl at google.com>
Date: Sun, 30 Mar 2025 23:32:41 +0000
Subject: [PATCH 1/2] lld keep data section prefix
---
lld/ELF/Config.h | 1 +
lld/ELF/Driver.cpp | 4 +++
lld/ELF/LinkerScript.cpp | 69 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 74 insertions(+)
diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index 03b3cd4771f49..0a01eddf20271 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -372,6 +372,7 @@ struct Config {
bool zInitfirst;
bool zInterpose;
bool zKeepTextSectionPrefix;
+ bool zKeepDataSectionPrefix;
bool zLrodataAfterBss;
bool zNoBtCfi;
bool zNodefaultlib;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 0a220432333cc..32ebd7a1a2ad9 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -1566,6 +1566,10 @@ static void readConfigs(Ctx &ctx, opt::InputArgList &args) {
ctx.arg.zInterpose = hasZOption(args, "interpose");
ctx.arg.zKeepTextSectionPrefix = getZFlag(
args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
+ ctx.arg.zKeepDataSectionPrefix = getZFlag(
+ args, "keep-data-section-prefix", "nokeep-data-section-prefix", false);
+ errs() << "ELF/Driver.cpp:1540\t" << ctx.arg.zKeepDataSectionPrefix << "\n";
+
ctx.arg.zLrodataAfterBss =
getZFlag(args, "lrodata-after-bss", "nolrodata-after-bss", false);
ctx.arg.zNoBtCfi = hasZOption(args, "nobtcfi");
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index e19823f2ea752..17432e65bb1bf 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -48,6 +48,11 @@ static bool isSectionPrefix(StringRef prefix, StringRef name) {
return name.consume_front(prefix) && (name.empty() || name[0] == '.');
}
+bool hasUnlikelySuffix(StringRef name) {
+ return name.ends_with(".unlikely") || name.ends_with(".unlikely.") ||
+ name.ends_with("unlikely");
+}
+
StringRef LinkerScript::getOutputSectionName(const InputSectionBase *s) const {
// This is for --emit-relocs and -r. If .text.foo is emitted as .text.bar, we
// want to emit .rela.text.foo as .rela.text.bar for consistency (this is not
@@ -105,6 +110,70 @@ StringRef LinkerScript::getOutputSectionName(const InputSectionBase *s) const {
return ".text";
}
+ if (isSectionPrefix(".data.rel.ro", s->name)) {
+ // Map input sections' .rodata and rodata.hot into .rodata.hot in the
+ // output. Map input sections' .rodata.unlikely into .rodata in the output.
+ if (ctx.arg.zKeepDataSectionPrefix) {
+ if (isSectionPrefix(".data.rel.ro.unlikely", s->name) ||
+ hasUnlikelySuffix(s->name)) {
+ return ".data.rel.ro.unlikely";
+ }
+
+ return ".data.rel.ro";
+ }
+ return ".data.rel.ro";
+ }
+
+ if (isSectionPrefix(".data", s->name)) {
+ // Map input sections' .rodata and rodata.hot into .rodata.hot in the
+ // output. Map input sections' .rodata.unlikely into .rodata in the output.
+ if (ctx.arg.zKeepDataSectionPrefix) {
+ if (isSectionPrefix(".data.unlikely", s->name) ||
+ hasUnlikelySuffix(s->name)) {
+ // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
+ return ".data.unlikely";
+ }
+
+ return ".data";
+ }
+ return ".data";
+ }
+
+ if (isSectionPrefix(".rodata", s->name)) {
+ // Map input sections' .rodata and rodata.hot into .rodata.hot in the
+ // output. Map input sections' .rodata.unlikely into .rodata in the output.
+ if (ctx.arg.zKeepDataSectionPrefix) {
+ // if (isSectionPrefix(".rodata.cst", s->name)) {
+ // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
+ //}
+ // .rodata.cst<N>.unlikely
+ // .rodata.str4.16.unlikely
+ if (isSectionPrefix(".rodata.unlikely", s->name) ||
+ hasUnlikelySuffix(s->name)) {
+ // return ".rodata.unlikely";
+ return ".rodata.unlikely";
+ }
+ return ".rodata";
+ }
+ return ".rodata";
+ }
+
+ if (isSectionPrefix(".bss.rel.ro", s->name)) {
+ return ".bss.rel.ro";
+ }
+
+ if (isSectionPrefix(".bss", s->name)) {
+ if (ctx.arg.zKeepDataSectionPrefix) {
+ if (isSectionPrefix(".bss.unlikely", s->name)) {
+ // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
+ return ".bss.unlikely";
+ }
+
+ return ".bss";
+ }
+ return ".bss";
+ }
+
for (StringRef v : {".data.rel.ro", ".data", ".rodata",
".bss.rel.ro", ".bss", ".ldata",
".lrodata", ".lbss", ".gcc_except_table",
>From 6328b71a44ebe50babcf766f9258df1f0dd8bb3d Mon Sep 17 00:00:00 2001
From: mingmingl <mingmingl at google.com>
Date: Sun, 20 Jul 2025 18:22:20 -0700
Subject: [PATCH 2/2] simplify implementation
---
lld/ELF/Config.h | 2 +-
lld/ELF/Driver.cpp | 5 +-
lld/ELF/LinkerScript.cpp | 99 ++++++++++++----------------------------
3 files changed, 33 insertions(+), 73 deletions(-)
diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index 0a01eddf20271..d3f6103fde4b7 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -371,8 +371,8 @@ struct Config {
bool zIfuncNoplt;
bool zInitfirst;
bool zInterpose;
- bool zKeepTextSectionPrefix;
bool zKeepDataSectionPrefix;
+ bool zKeepTextSectionPrefix;
bool zLrodataAfterBss;
bool zNoBtCfi;
bool zNodefaultlib;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 32ebd7a1a2ad9..cd48f0f64ce29 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -1564,11 +1564,10 @@ static void readConfigs(Ctx &ctx, opt::InputArgList &args) {
ctx.arg.zIfuncNoplt = hasZOption(args, "ifunc-noplt");
ctx.arg.zInitfirst = hasZOption(args, "initfirst");
ctx.arg.zInterpose = hasZOption(args, "interpose");
- ctx.arg.zKeepTextSectionPrefix = getZFlag(
- args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
ctx.arg.zKeepDataSectionPrefix = getZFlag(
args, "keep-data-section-prefix", "nokeep-data-section-prefix", false);
- errs() << "ELF/Driver.cpp:1540\t" << ctx.arg.zKeepDataSectionPrefix << "\n";
+ ctx.arg.zKeepTextSectionPrefix = getZFlag(
+ args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
ctx.arg.zLrodataAfterBss =
getZFlag(args, "lrodata-after-bss", "nolrodata-after-bss", false);
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 17432e65bb1bf..f1f8f6c776c7a 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -48,9 +48,9 @@ static bool isSectionPrefix(StringRef prefix, StringRef name) {
return name.consume_front(prefix) && (name.empty() || name[0] == '.');
}
-bool hasUnlikelySuffix(StringRef name) {
- return name.ends_with(".unlikely") || name.ends_with(".unlikely.") ||
- name.ends_with("unlikely");
+static bool isSectionSuffix(StringRef suffix, StringRef name) {
+ name.consume_back(".");
+ return name.ends_with(suffix);
}
StringRef LinkerScript::getOutputSectionName(const InputSectionBase *s) const {
@@ -110,77 +110,38 @@ StringRef LinkerScript::getOutputSectionName(const InputSectionBase *s) const {
return ".text";
}
- if (isSectionPrefix(".data.rel.ro", s->name)) {
- // Map input sections' .rodata and rodata.hot into .rodata.hot in the
- // output. Map input sections' .rodata.unlikely into .rodata in the output.
- if (ctx.arg.zKeepDataSectionPrefix) {
- if (isSectionPrefix(".data.rel.ro.unlikely", s->name) ||
- hasUnlikelySuffix(s->name)) {
- return ".data.rel.ro.unlikely";
- }
-
- return ".data.rel.ro";
- }
- return ".data.rel.ro";
- }
-
- if (isSectionPrefix(".data", s->name)) {
- // Map input sections' .rodata and rodata.hot into .rodata.hot in the
- // output. Map input sections' .rodata.unlikely into .rodata in the output.
- if (ctx.arg.zKeepDataSectionPrefix) {
- if (isSectionPrefix(".data.unlikely", s->name) ||
- hasUnlikelySuffix(s->name)) {
- // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
- return ".data.unlikely";
- }
-
- return ".data";
- }
- return ".data";
- }
-
- if (isSectionPrefix(".rodata", s->name)) {
- // Map input sections' .rodata and rodata.hot into .rodata.hot in the
- // output. Map input sections' .rodata.unlikely into .rodata in the output.
- if (ctx.arg.zKeepDataSectionPrefix) {
- // if (isSectionPrefix(".rodata.cst", s->name)) {
- // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
- //}
- // .rodata.cst<N>.unlikely
- // .rodata.str4.16.unlikely
- if (isSectionPrefix(".rodata.unlikely", s->name) ||
- hasUnlikelySuffix(s->name)) {
- // return ".rodata.unlikely";
- return ".rodata.unlikely";
- }
- return ".rodata";
- }
- return ".rodata";
- }
-
- if (isSectionPrefix(".bss.rel.ro", s->name)) {
- return ".bss.rel.ro";
- }
+ // When zKeepDataSectionPrefix is true, keep .hot and .unlikely suffixes
+ // in data sections.
+ static constexpr StringRef dataSectionPrefixes[] = {
+ ".data.rel.ro", ".data", ".rodata", ".bss.rel.ro", ".bss",
+ };
- if (isSectionPrefix(".bss", s->name)) {
- if (ctx.arg.zKeepDataSectionPrefix) {
- if (isSectionPrefix(".bss.unlikely", s->name)) {
- // errs() << "LinkerScript.cpp:100\t" << s->name << "\n";
- return ".bss.unlikely";
+ for (auto [index, v] : llvm::enumerate(dataSectionPrefixes)) {
+ if (isSectionPrefix(v, s->name)) {
+ if (ctx.arg.zKeepDataSectionPrefix) {
+ if (isSectionPrefix(".hot", s->name.substr(v.size())))
+ return s->name.substr(0, v.size() + 4);
+ if (isSectionPrefix(".unlikely", s->name.substr(v.size())))
+ return s->name.substr(0, v.size() + 9);
+ // for .rodata, a section could be`.rodata.cst<N>.hot.` for constant
+ // pool or `rodata.str<N>.hot.` for string literals.
+ if (index == 2) {
+ if (isSectionSuffix(".hot", s->name)) {
+ return ".rodata.hot";
+ }
+ if (isSectionSuffix(".unlikely", s->name)) {
+ return ".rodata.unlikely";
+ }
+ }
}
-
- return ".bss";
+ return v;
}
- return ".bss";
}
- for (StringRef v : {".data.rel.ro", ".data", ".rodata",
- ".bss.rel.ro", ".bss", ".ldata",
- ".lrodata", ".lbss", ".gcc_except_table",
- ".init_array", ".fini_array", ".tbss",
- ".tdata", ".ARM.exidx", ".ARM.extab",
- ".ctors", ".dtors", ".sbss",
- ".sdata", ".srodata"})
+ for (StringRef v :
+ {".ldata", ".lrodata", ".lbss", ".gcc_except_table", ".init_array",
+ ".fini_array", ".tbss", ".tdata", ".ARM.exidx", ".ARM.extab", ".ctors",
+ ".dtors", ".sbss", ".sdata", ".srodata"})
if (isSectionPrefix(v, s->name))
return v;
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