[lld] [ELF] Keep non-alloc orphan sections at the end (PR #94519)
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 5 11:35:04 PDT 2024
https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/94519
https://reviews.llvm.org/D85867 changed the way we assign file offsets
(alloc sections first, then non-alloc sections).
It also removed a non-alloc special case from `findOrphanPos`.
Looking at the memory-nonalloc-no-warn.test change, which would be
needed by #93761, it makes sense to restore the previous behavior: when
placing non-alloc orphan sections, keep these sections at the end so
that the section index order matches the file offset order.
This change is cosmetic. In sections-nonalloc.s, GNU ld places the
orphan `other3` in the middle and the orphan .symtab/.shstrtab/.strtab
at the end.
>From 0da2a7f9960d77eb559688db965c29cb31756ad5 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Wed, 5 Jun 2024 11:34:54 -0700
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.5-bogner
---
lld/ELF/Writer.cpp | 6 +++-
.../linkerscript/memory-nonalloc-no-warn.test | 22 +++++++--------
lld/test/ELF/linkerscript/sections-nonalloc.s | 28 +++++++++----------
lld/test/ELF/linkerscript/sections.s | 4 +--
4 files changed, 32 insertions(+), 28 deletions(-)
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 0295a656b0705..ff6d9beb3731e 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -921,7 +921,11 @@ static bool shouldSkip(SectionCommand *cmd) {
static SmallVectorImpl<SectionCommand *>::iterator
findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
SmallVectorImpl<SectionCommand *>::iterator e) {
+ // Place non-alloc orphan sections at the end. This matches how we assign file
+ // offsets to non-alloc sections.
OutputSection *sec = &cast<OutputDesc>(*e)->osec;
+ if (!(sec->flags & SHF_ALLOC))
+ return e;
// As a special case, place .relro_padding before the SymbolAssignment using
// DATA_SEGMENT_RELRO_END, if present.
@@ -1316,8 +1320,8 @@ template <class ELFT> void Writer<ELFT>::sortOrphanSections() {
i = firstSectionOrDotAssignment;
while (nonScriptI != e) {
- auto pos = findOrphanPos(i, nonScriptI);
OutputSection *orphan = &cast<OutputDesc>(*nonScriptI)->osec;
+ auto pos = findOrphanPos(i, nonScriptI);
// As an optimization, find all sections with the same sort rank
// and insert them with one rotate.
diff --git a/lld/test/ELF/linkerscript/memory-nonalloc-no-warn.test b/lld/test/ELF/linkerscript/memory-nonalloc-no-warn.test
index 2dcd0f8d6ce2f..eabdf75fcf935 100644
--- a/lld/test/ELF/linkerscript/memory-nonalloc-no-warn.test
+++ b/lld/test/ELF/linkerscript/memory-nonalloc-no-warn.test
@@ -16,20 +16,20 @@
## The output file must include all sections.
# RUN: llvm-readelf -S %t/a.elf | FileCheck %s
-# CHECK: There are 12 section headers, starting at offset 0x2140:
+# CHECK: There are 12 section headers, starting at offset 0x2138:
# CHECK: [Nr] Name Type Address Off Size ES Flg Lk Inf Al
# CHECK-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0 0 0
# CHECK-NEXT: [ 1] .nonalloc PROGBITS 0000000000000000 001064 001000 00 W 0 0 1
-# CHECK-NEXT: [ 2] .comment PROGBITS 0000000000000000 {{.*}} {{.*}} 01 MS 0 0 1
-# CHECK-NEXT: [ 3] .symtab SYMTAB 0000000000000000 {{.*}} {{.*}} 18 5 1 8
-# CHECK-NEXT: [ 4] .shstrtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
-# CHECK-NEXT: [ 5] .strtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
-# CHECK-NEXT: [ 6] .dat PROGBITS 0000000000000000 002137 000004 00 W 0 0 1
-# CHECK-NEXT: [ 7] .intvec0_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
-# CHECK-NEXT: [ 8] .intvec1_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
-# CHECK-NEXT: [ 9] .intvec2_out PROGBITS 0000000000000000 00213b 000000 00 W 0 0 1
-# CHECK-NEXT: [10] .intvec3_out PROGBITS 00000000803fe060 001060 000004 00 AX 0 0 1
-# CHECK-NEXT: [11] .text PROGBITS 00000000803fe064 001064 000000 00 AX 0 0 4
+# CHECK-NEXT: [ 2] .dat PROGBITS 0000000000000000 002064 000004 00 W 0 0 1
+# CHECK-NEXT: [ 3] .intvec0_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
+# CHECK-NEXT: [ 4] .intvec1_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
+# CHECK-NEXT: [ 5] .intvec2_out PROGBITS 0000000000000000 002068 000000 00 W 0 0 1
+# CHECK-NEXT: [ 6] .intvec3_out PROGBITS 00000000803fe060 001060 000004 00 AX 0 0 1
+# CHECK-NEXT: [ 7] .text PROGBITS 00000000803fe064 001064 000000 00 AX 0 0 4
+# CHECK-NEXT: [ 8] .comment PROGBITS 0000000000000000 {{.*}} {{.*}} 01 MS 0 0 1
+# CHECK-NEXT: [ 9] .symtab SYMTAB 0000000000000000 {{.*}} {{.*}} 18 11 1 8
+# CHECK-NEXT: [10] .shstrtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
+# CHECK-NEXT: [11] .strtab STRTAB 0000000000000000 {{.*}} {{.*}} 00 0 0 1
#--- a.s
diff --git a/lld/test/ELF/linkerscript/sections-nonalloc.s b/lld/test/ELF/linkerscript/sections-nonalloc.s
index 79765d32dfffe..b4fab8c24cfb4 100644
--- a/lld/test/ELF/linkerscript/sections-nonalloc.s
+++ b/lld/test/ELF/linkerscript/sections-nonalloc.s
@@ -16,15 +16,15 @@
# CHECK-NEXT: [ 2] data1 PROGBITS 0000000000000001 001001 000001 00 WA 0
# CHECK-NEXT: [ 3] other1 PROGBITS 0000000000000000 001008 000001 00 0
# CHECK-NEXT: [ 4] other2 PROGBITS 0000000000000000 001010 000001 00 0
-## Orphan placement places other3, .symtab, .shstrtab and .strtab after other2.
-# CHECK-NEXT: [ 5] other3 PROGBITS 0000000000000000 001020 000001 00 0
-# CHECK-NEXT: [ 6] .symtab SYMTAB 0000000000000000 001028 000030 18 8
-# CHECK-NEXT: [ 7] .shstrtab STRTAB 0000000000000000 001058 00004d 00 0
-# CHECK-NEXT: [ 8] .strtab STRTAB 0000000000000000 0010a5 000008 00 0
-# CHECK-NEXT: [ 9] data2 PROGBITS 0000000000000002 001002 000001 00 WA 0
+# CHECK-NEXT: [ 5] data2 PROGBITS 0000000000000002 001002 000001 00 WA 0
## max{sortRank(data1),sortRank(data2)} <= sortRank(data3). data3 is placed after the latter.
-# CHECK-NEXT: [10] data3 PROGBITS 0000000000000003 001003 000001 00 WA 0
-# CHECK-NEXT: [11] .text PROGBITS 0000000000000004 001004 000001 00 AX 0
+# CHECK-NEXT: [ 6] data3 PROGBITS 0000000000000003 001003 000001 00 WA 0
+# CHECK-NEXT: [ 7] .text PROGBITS 0000000000000004 001004 000001 00 AX 0
+## Non-alloc orphan sections other3, .symtab, .shstrtab and .strtab are placed at the end.
+# CHECK-NEXT: [ 8] other3 PROGBITS 0000000000000000 001020 000001 00 0
+# CHECK-NEXT: [ 9] .symtab SYMTAB 0000000000000000 001028 000030 18 11
+# CHECK-NEXT: [10] .shstrtab STRTAB 0000000000000000 001058 00004d 00 0
+# CHECK-NEXT: [11] .strtab STRTAB 0000000000000000 0010a5 000008 00 0
# CHECK: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
# CHECK-NEXT: LOAD 0x001000 0x0000000000000000 0x0000000000000000 0x000004 0x000004 RW 0x1000
@@ -41,12 +41,12 @@
# CHECK1-NEXT: [ 3] data1 PROGBITS 00000000000000b2 0000b2 000001 00 WA 0
# CHECK1-NEXT: [ 4] other1 PROGBITS 0000000000000000 0000b8 000001 00 0
# CHECK1-NEXT: [ 5] other2 PROGBITS 0000000000000000 0000c0 000001 00 0
-# CHECK1-NEXT: [ 6] other3 PROGBITS 0000000000000000 0000d0 000001 00 0
-# CHECK1-NEXT: [ 7] .symtab SYMTAB 0000000000000000 0000d8 000030 18 9
-# CHECK1-NEXT: [ 8] .shstrtab STRTAB 0000000000000000 000108 00004d 00 0
-# CHECK1-NEXT: [ 9] .strtab STRTAB 0000000000000000 000155 000008 00 0
-# CHECK1-NEXT: [10] data2 PROGBITS 00000000000000b3 0000b3 000001 00 WA 0
-# CHECK1-NEXT: [11] data3 PROGBITS 00000000000000b4 0000b4 000001 00 WA 0
+# CHECK1-NEXT: [ 6] data2 PROGBITS 00000000000000b3 0000b3 000001 00 WA 0
+# CHECK1-NEXT: [ 7] data3 PROGBITS 00000000000000b4 0000b4 000001 00 WA 0
+# CHECK1-NEXT: [ 8] other3 PROGBITS 0000000000000000 0000d0 000001 00 0
+# CHECK1-NEXT: [ 9] .symtab SYMTAB 0000000000000000 0000d8 000030 18 11
+# CHECK1-NEXT: [10] .shstrtab STRTAB 0000000000000000 000108 00004d 00 0
+# CHECK1-NEXT: [11] .strtab STRTAB 0000000000000000 000155 000008 00 0
# CHECK1: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
# CHECK1-NEXT: LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x0000b5 0x0000b5 RWE 0x1000
# CHECK1-NEXT: 0x60000000 0x0000b8 0x0000000000000000 0x0000000000000000 0x000009 0x000001 0x8
diff --git a/lld/test/ELF/linkerscript/sections.s b/lld/test/ELF/linkerscript/sections.s
index 5d6cc1f3bd0df..fc03af8402dfe 100644
--- a/lld/test/ELF/linkerscript/sections.s
+++ b/lld/test/ELF/linkerscript/sections.s
@@ -79,8 +79,8 @@
# SEP-BY-NONALLOC: [ 1] .text PROGBITS 0000000000000000 001000 00000e 00 AX
# SEP-BY-NONALLOC-NEXT: [ 2] .data PROGBITS 000000000000000e 00100e 000020 00 WA
# SEP-BY-NONALLOC-NEXT: [ 3] .comment PROGBITS 0000000000000000 001031 000008 01 MS
-# SEP-BY-NONALLOC: [ 7] other PROGBITS 000000000000002e 00102e 000003 00 WA
-# SEP-BY-NONALLOC-NEXT: [ 8] .bss NOBITS 0000000000000031 001031 000002 00 WA
+# SEP-BY-NONALLOC: [ 4] other PROGBITS 000000000000002e 00102e 000003 00 WA
+# SEP-BY-NONALLOC-NEXT: [ 5] .bss NOBITS 0000000000000031 001031 000002 00 WA
# SEP-BY-NONALLOC: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
# SEP-BY-NONALLOC-NEXT: LOAD 0x001000 0x0000000000000000 0x0000000000000000 0x00000e 0x00000e R E 0x1000
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