[lld] [lld] Mark target section as code section when merging code sections into a data section. (PR #72030)
Jacek Caban via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 13 09:12:24 PST 2023
https://github.com/cjacek updated https://github.com/llvm/llvm-project/pull/72030
>From c106cc3caa59052b7ba2982ffe804ad09844d3aa Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Mon, 13 Nov 2023 17:39:11 +0100
Subject: [PATCH 1/2] [lld][COFF] Fill only gaps in code sections.
Filling entire buffer would require all chunks to overwrite it later, which is not the case for uninitialized chunks merged into a code section.
---
lld/COFF/Writer.cpp | 12 ++-
lld/test/COFF/code-merge.s | 146 +++++++++++++++++++++++++++++++++++++
2 files changed, 156 insertions(+), 2 deletions(-)
create mode 100644 lld/test/COFF/code-merge.s
diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index 960328d686852a3..9be4cbb1757ca07 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -2020,8 +2020,16 @@ void Writer::writeSections() {
// instead of leaving as NUL bytes (which can be interpreted as
// ADD instructions).
if ((sec->header.Characteristics & IMAGE_SCN_CNT_CODE) &&
- (ctx.config.machine == AMD64 || ctx.config.machine == I386))
- memset(secBuf, 0xCC, sec->getRawSize());
+ (ctx.config.machine == AMD64 || ctx.config.machine == I386)) {
+ uint32_t prevEnd = 0;
+ for (Chunk *c : sec->chunks) {
+ uint32_t off = c->getRVA() - sec->getRVA();
+ memset(secBuf + prevEnd, 0xCC, off - prevEnd);
+ prevEnd = off + c->getSize();
+ }
+ memset(secBuf + prevEnd, 0xCC, sec->getRawSize() - prevEnd);
+ }
+
parallelForEach(sec->chunks, [&](Chunk *c) {
c->writeTo(secBuf + c->getRVA() - sec->getRVA());
});
diff --git a/lld/test/COFF/code-merge.s b/lld/test/COFF/code-merge.s
new file mode 100644
index 000000000000000..e7aa86533ce547a
--- /dev/null
+++ b/lld/test/COFF/code-merge.s
@@ -0,0 +1,146 @@
+# REQUIRES: x86
+
+# Test merging code sections with data sections.
+
+# RUN: llvm-mc -triple x86_64-windows-msvc %s -filetype=obj -o %t.obj
+# RUN: lld-link -machine:amd64 -dll -noentry -out:%t.dll %t.obj -merge:.testx=.testd -merge:.testx2=.testbss -merge:.testd2=.testx3 -merge:.testbss2=.testx4
+
+# RUN: llvm-readobj --sections %t.dll | FileCheck %s
+# CHECK: Sections [
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 1
+# CHECK-NEXT: Name: .testbss (2E 74 65 73 74 62 73 73)
+# CHECK-NEXT: VirtualSize: 0x18
+# CHECK-NEXT: VirtualAddress: 0x1000
+# CHECK-NEXT: RawDataSize: 512
+# CHECK-NEXT: PointerToRawData: 0x400
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0xC0000080)
+# CHECK-NEXT: IMAGE_SCN_CNT_UNINITIALIZED_DATA (0x80)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_WRITE (0x80000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 2
+# CHECK-NEXT: Name: .testd (2E 74 65 73 74 64 00 00)
+# CHECK-NEXT: VirtualSize: 0x18
+# CHECK-NEXT: VirtualAddress: 0x2000
+# CHECK-NEXT: RawDataSize: 512
+# CHECK-NEXT: PointerToRawData: 0x600
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0x40000040)
+# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 3
+# CHECK-NEXT: Name: .testx3 (2E 74 65 73 74 78 33 00)
+# CHECK-NEXT: VirtualSize: 0x12
+# CHECK-NEXT: VirtualAddress: 0x3000
+# CHECK-NEXT: RawDataSize: 512
+# CHECK-NEXT: PointerToRawData: 0x800
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0x60000020)
+# CHECK-NEXT: IMAGE_SCN_CNT_CODE (0x20)
+# CHECK-NEXT: IMAGE_SCN_MEM_EXECUTE (0x20000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 4
+# CHECK-NEXT: Name: .testx4 (2E 74 65 73 74 78 34 00)
+# CHECK-NEXT: VirtualSize: 0x14
+# CHECK-NEXT: VirtualAddress: 0x4000
+# CHECK-NEXT: RawDataSize: 512
+# CHECK-NEXT: PointerToRawData: 0xA00
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0x60000020)
+# CHECK-NEXT: IMAGE_SCN_CNT_CODE (0x20)
+# CHECK-NEXT: IMAGE_SCN_MEM_EXECUTE (0x20000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: ]
+
+# RUN: llvm-objdump -d %t.dll | FileCheck -check-prefix=DISASM %s
+# DISASM: Disassembly of section .testx3:
+# DISASM-EMPTY:
+# DISASM-NEXT: 0000000180003000 <.testx3>:
+# DISASM-NEXT: 180003000: 48 c7 c0 03 00 00 00 movq $0x3, %rax
+# DISASM-NEXT: 180003007: c3 retq
+# DISASM-NEXT: 180003008: cc int3
+# DISASM-NEXT: 180003009: cc int3
+# DISASM-NEXT: 18000300a: cc int3
+# DISASM-NEXT: 18000300b: cc int3
+# DISASM-NEXT: 18000300c: cc int3
+# DISASM-NEXT: 18000300d: cc int3
+# DISASM-NEXT: 18000300e: cc int3
+# DISASM-NEXT: 18000300f: cc int3
+# DISASM-NEXT: 180003010: 02 00 addb (%rax), %al
+# DISASM-EMPTY:
+# DISASM-NEXT: Disassembly of section .testx4:
+# DISASM-EMPTY:
+# DISASM-NEXT: 0000000180004000 <.testx4>:
+# DISASM-NEXT: 180004000: 48 c7 c0 04 00 00 00 movq $0x4, %rax
+# DISASM-NEXT: 180004007: c3 retq
+# DISASM-NEXT: 180004008: cc int3
+# DISASM-NEXT: 180004009: cc int3
+# DISASM-NEXT: 18000400a: cc int3
+# DISASM-NEXT: 18000400b: cc int3
+# DISASM-NEXT: 18000400c: cc int3
+# DISASM-NEXT: 18000400d: cc int3
+# DISASM-NEXT: 18000400e: cc int3
+# DISASM-NEXT: 18000400f: cc int3
+# DISASM-NEXT: 180004010: 00 00 addb %al, (%rax)
+# DISASM-NEXT: 180004012: 00 00 addb %al, (%rax)
+
+
+ .section .testx, "xr"
+ .p2align 4
+ movq $1, %rax
+ retq
+
+ .section .testx2, "xr"
+ .p2align 4
+ movq $2, %rax
+ retq
+
+ .section .testd, "dr"
+ .p2align 4
+ .word 1
+
+ .section .testbss, "b"
+ .p2align 4
+ .skip 4
+
+ .section .testx3, "xr"
+ .p2align 4
+ movq $3, %rax
+ retq
+
+ .section .testx4, "xr"
+ .p2align 4
+ movq $4, %rax
+ retq
+
+ .section .testd2, "dr"
+ .p2align 4
+ .word 2
+
+ .section .testbss2, "b"
+ .p2align 4
+ .skip 4
>From fe622d002d540ed95aed148f10a581a70ef3cc19 Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Mon, 13 Nov 2023 17:59:51 +0100
Subject: [PATCH 2/2] [lld] Mark target section as code section when merging
code sections into a data section.
---
lld/COFF/Writer.cpp | 8 ++++++
lld/test/COFF/code-merge.s | 51 ++++++++++++++++++++++++++++++++++----
2 files changed, 54 insertions(+), 5 deletions(-)
diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index 9be4cbb1757ca07..2c4bde9abc72b8e 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -346,6 +346,14 @@ void OutputSection::merge(OutputSection *other) {
contribSections.insert(contribSections.end(), other->contribSections.begin(),
other->contribSections.end());
other->contribSections.clear();
+
+ // MS link.exe compatibility: when merging a code section into a data section,
+ // mark the target section as a code section.
+ if (other->header.Characteristics & IMAGE_SCN_CNT_CODE) {
+ header.Characteristics |= IMAGE_SCN_CNT_CODE;
+ header.Characteristics &=
+ ~(IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_CNT_UNINITIALIZED_DATA);
+ }
}
// Write the section header to a given buffer.
diff --git a/lld/test/COFF/code-merge.s b/lld/test/COFF/code-merge.s
index e7aa86533ce547a..31ccd081145b068 100644
--- a/lld/test/COFF/code-merge.s
+++ b/lld/test/COFF/code-merge.s
@@ -18,8 +18,8 @@
# CHECK-NEXT: PointerToLineNumbers: 0x0
# CHECK-NEXT: RelocationCount: 0
# CHECK-NEXT: LineNumberCount: 0
-# CHECK-NEXT: Characteristics [ (0xC0000080)
-# CHECK-NEXT: IMAGE_SCN_CNT_UNINITIALIZED_DATA (0x80)
+# CHECK-NEXT: Characteristics [ (0xC0000020)
+# CHECK-NEXT: IMAGE_SCN_CNT_CODE (0x20)
# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
# CHECK-NEXT: IMAGE_SCN_MEM_WRITE (0x80000000)
# CHECK-NEXT: ]
@@ -35,8 +35,8 @@
# CHECK-NEXT: PointerToLineNumbers: 0x0
# CHECK-NEXT: RelocationCount: 0
# CHECK-NEXT: LineNumberCount: 0
-# CHECK-NEXT: Characteristics [ (0x40000040)
-# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
+# CHECK-NEXT: Characteristics [ (0x40000020)
+# CHECK-NEXT: IMAGE_SCN_CNT_CODE (0x20)
# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
# CHECK-NEXT: ]
# CHECK-NEXT: }
@@ -77,7 +77,48 @@
# CHECK-NEXT: ]
# RUN: llvm-objdump -d %t.dll | FileCheck -check-prefix=DISASM %s
-# DISASM: Disassembly of section .testx3:
+# DISASM: Disassembly of section .testbss:
+# DISASM-EMPTY:
+# DISASM-NEXT: 0000000180001000 <.testbss>:
+# DISASM-NEXT: 180001000: 00 00 addb %al, (%rax)
+# DISASM-NEXT: 180001002: 00 00 addb %al, (%rax)
+# DISASM-NEXT: 180001004: cc int3
+# DISASM-NEXT: 180001005: cc int3
+# DISASM-NEXT: 180001006: cc int3
+# DISASM-NEXT: 180001007: cc int3
+# DISASM-NEXT: 180001008: cc int3
+# DISASM-NEXT: 180001009: cc int3
+# DISASM-NEXT: 18000100a: cc int3
+# DISASM-NEXT: 18000100b: cc int3
+# DISASM-NEXT: 18000100c: cc int3
+# DISASM-NEXT: 18000100d: cc int3
+# DISASM-NEXT: 18000100e: cc int3
+# DISASM-NEXT: 18000100f: cc int3
+# DISASM-NEXT: 180001010: 48 c7 c0 02 00 00 00 movq $0x2, %rax
+# DISASM-NEXT: 180001017: c3 retq
+# DISASM-EMPTY:
+# DISASM-NEXT: Disassembly of section .testd:
+# DISASM-EMPTY:
+# DISASM-NEXT: 0000000180002000 <.testd>:
+# DISASM-NEXT: 180002000: 01 00 addl %eax, (%rax)
+# DISASM-NEXT: 180002002: cc int3
+# DISASM-NEXT: 180002003: cc int3
+# DISASM-NEXT: 180002004: cc int3
+# DISASM-NEXT: 180002005: cc int3
+# DISASM-NEXT: 180002006: cc int3
+# DISASM-NEXT: 180002007: cc int3
+# DISASM-NEXT: 180002008: cc int3
+# DISASM-NEXT: 180002009: cc int3
+# DISASM-NEXT: 18000200a: cc int3
+# DISASM-NEXT: 18000200b: cc int3
+# DISASM-NEXT: 18000200c: cc int3
+# DISASM-NEXT: 18000200d: cc int3
+# DISASM-NEXT: 18000200e: cc int3
+# DISASM-NEXT: 18000200f: cc int3
+# DISASM-NEXT: 180002010: 48 c7 c0 01 00 00 00 movq $0x1, %rax
+# DISASM-NEXT: 180002017: c3 retq
+# DISASM-EMPTY:
+# DISASM-NEXT: Disassembly of section .testx3:
# DISASM-EMPTY:
# DISASM-NEXT: 0000000180003000 <.testx3>:
# DISASM-NEXT: 180003000: 48 c7 c0 03 00 00 00 movq $0x3, %rax
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