[lld] ELF: Have __rela_iplt_{start,end} surround .rela.iplt with --pack-dyn-relocs=android. (PR #118585)
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Tue Dec 3 19:20:22 PST 2024
https://github.com/pcc updated https://github.com/llvm/llvm-project/pull/118585
>From 41c06d176db62940e0f9fbced5bb4e87c5494ded Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter at pcc.me.uk>
Date: Tue, 3 Dec 2024 19:14:40 -0800
Subject: [PATCH 1/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20in?=
=?UTF-8?q?itial=20version?=
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Created using spr 1.3.6-beta.1
---
lld/ELF/Relocations.cpp | 20 +++++++++-------
lld/ELF/Relocations.h | 3 +++
lld/ELF/Writer.cpp | 14 +++++++----
lld/test/ELF/pack-dyn-relocs-ifunc-static.s | 26 +++++++++++++++++++++
4 files changed, 49 insertions(+), 14 deletions(-)
create mode 100644 lld/test/ELF/pack-dyn-relocs-ifunc-static.s
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 4aa27b0a71bc1d..204599c544bc44 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -1687,6 +1687,16 @@ template <class ELFT> void elf::scanRelocations(Ctx &ctx) {
outerFn();
}
+RelocationBaseSection &elf::getIRelativeSection(Ctx &ctx) {
+ // Prior to Android V, there was a bug that caused RELR relocations to be
+ // applied after packed relocations. This meant that resolvers referenced by
+ // IRELATIVE relocations in the packed relocation section would read
+ // unrelocated globals with RELR relocations when
+ // --pack-relative-relocs=android+relr is enabled. Work around this by placing
+ // IRELATIVE in .rela.plt.
+ return ctx.arg.androidPackDynRelocs ? *ctx.in.relaPlt : *ctx.mainPart->relaDyn;
+}
+
static bool handleNonPreemptibleIfunc(Ctx &ctx, Symbol &sym, uint16_t flags) {
// Handle a reference to a non-preemptible ifunc. These are special in a
// few ways:
@@ -1736,17 +1746,9 @@ static bool handleNonPreemptibleIfunc(Ctx &ctx, Symbol &sym, uint16_t flags) {
// original section/value pairs. For non-GOT non-PLT relocation case below, we
// may alter section/value, so create a copy of the symbol to make
// section/value fixed.
- //
- // Prior to Android V, there was a bug that caused RELR relocations to be
- // applied after packed relocations. This meant that resolvers referenced by
- // IRELATIVE relocations in the packed relocation section would read
- // unrelocated globals with RELR relocations when
- // --pack-relative-relocs=android+relr is enabled. Work around this by placing
- // IRELATIVE in .rela.plt.
auto *directSym = makeDefined(cast<Defined>(sym));
directSym->allocateAux(ctx);
- auto &dyn =
- ctx.arg.androidPackDynRelocs ? *ctx.in.relaPlt : *ctx.mainPart->relaDyn;
+ auto &dyn = getIRelativeSection(ctx);
addPltEntry(ctx, *ctx.in.iplt, *ctx.in.igotPlt, dyn, ctx.target->iRelativeRel,
*directSym);
sym.allocateAux(ctx);
diff --git a/lld/ELF/Relocations.h b/lld/ELF/Relocations.h
index 71cea0220e04c3..7ca203257ea876 100644
--- a/lld/ELF/Relocations.h
+++ b/lld/ELF/Relocations.h
@@ -22,6 +22,7 @@ class Symbol;
class InputSection;
class InputSectionBase;
class OutputSection;
+class RelocationBaseSection;
class SectionBase;
// Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
@@ -356,6 +357,8 @@ sortRels(Relocs<llvm::object::Elf_Crel_Impl<is64>> rels,
return {};
}
+RelocationBaseSection &getIRelativeSection(Ctx &ctx);
+
// Returns true if Expr refers a GOT entry. Note that this function returns
// false for TLS variables even though they need GOT, because TLS variables uses
// GOT differently than the regular variables.
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index f10cc54c05a0ca..aa7c36bc9ac13b 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -844,11 +844,15 @@ template <class ELFT> void Writer<ELFT>::setReservedSymbolSections() {
ctx.sym.globalOffsetTable->section = sec;
}
- // .rela_iplt_{start,end} mark the start and the end of .rel[a].dyn.
- if (ctx.sym.relaIpltStart && ctx.mainPart->relaDyn->isNeeded()) {
- ctx.sym.relaIpltStart->section = ctx.mainPart->relaDyn.get();
- ctx.sym.relaIpltEnd->section = ctx.mainPart->relaDyn.get();
- ctx.sym.relaIpltEnd->value = ctx.mainPart->relaDyn->getSize();
+ // .rela_iplt_{start,end} mark the start and the end of the section containing
+ // IRELATIVE relocations.
+ if (ctx.sym.relaIpltStart) {
+ auto &dyn = getIRelativeSection(ctx);
+ if (dyn.isNeeded()) {
+ ctx.sym.relaIpltStart->section = &dyn;
+ ctx.sym.relaIpltEnd->section = &dyn;
+ ctx.sym.relaIpltEnd->value = dyn.getSize();
+ }
}
PhdrEntry *last = nullptr;
diff --git a/lld/test/ELF/pack-dyn-relocs-ifunc-static.s b/lld/test/ELF/pack-dyn-relocs-ifunc-static.s
new file mode 100644
index 00000000000000..0f86a6db785b61
--- /dev/null
+++ b/lld/test/ELF/pack-dyn-relocs-ifunc-static.s
@@ -0,0 +1,26 @@
+# REQUIRES: aarch64
+## __rela_iplt_start and __rela_iplt_end must surround the IRELATIVE relocation
+## list even if moved to .rel[a].plt because of packed relocation sections.
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-linux-android %s -o %t.o
+# RUN: ld.lld --pack-dyn-relocs=android %t.o -o %t
+# RUN: llvm-readelf -sS %t | FileCheck %s
+
+# CHECK: .rela.plt RELA 0000000000200158 000158 000018 18 AI 0 5 8
+# CHECK: 0000000000200158 0 NOTYPE LOCAL HIDDEN 1 __rela_iplt_start
+# CHECK: 0000000000200170 0 NOTYPE LOCAL HIDDEN 1 __rela_iplt_end
+
+.text
+.type foo, %gnu_indirect_function
+.globl foo
+foo:
+ ret
+
+.globl _start
+_start:
+ bl foo
+
+.data
+.balign 8
+.quad __rela_iplt_start
+.quad __rela_iplt_end
>From ade32a0d39ef4158a10edd875d075010ad1c864c Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter at pcc.me.uk>
Date: Tue, 3 Dec 2024 19:20:09 -0800
Subject: [PATCH 2/2] Format
Created using spr 1.3.6-beta.1
---
lld/ELF/Relocations.cpp | 3 ++-
lld/ELF/Writer.cpp | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 204599c544bc44..2268121827f649 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -1694,7 +1694,8 @@ RelocationBaseSection &elf::getIRelativeSection(Ctx &ctx) {
// unrelocated globals with RELR relocations when
// --pack-relative-relocs=android+relr is enabled. Work around this by placing
// IRELATIVE in .rela.plt.
- return ctx.arg.androidPackDynRelocs ? *ctx.in.relaPlt : *ctx.mainPart->relaDyn;
+ return ctx.arg.androidPackDynRelocs ? *ctx.in.relaPlt
+ : *ctx.mainPart->relaDyn;
}
static bool handleNonPreemptibleIfunc(Ctx &ctx, Symbol &sym, uint16_t flags) {
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index aa7c36bc9ac13b..49616fa03e63c6 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -847,7 +847,7 @@ template <class ELFT> void Writer<ELFT>::setReservedSymbolSections() {
// .rela_iplt_{start,end} mark the start and the end of the section containing
// IRELATIVE relocations.
if (ctx.sym.relaIpltStart) {
- auto &dyn = getIRelativeSection(ctx);
+ auto &dyn = getIRelativeSection(ctx);
if (dyn.isNeeded()) {
ctx.sym.relaIpltStart->section = &dyn;
ctx.sym.relaIpltEnd->section = &dyn;
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