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[lld] Fill .text section gaps with INT3 only on x86 targets.

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It doesn't make sense on ARM and using default 0 fill is compatible
with MSVC.

(It's more noticeable ARM64EC targets, where additional padding mixed
with alignment is used for entry thunk association, so there are more
gaps).

Reviewed By: mstorsjo

Differential Revision: https://reviews.llvm.org/D145962
This commit is contained in:
Jacek Caban 2023-03-23 13:20:37 +02:00 committed by Martin Storsjö
parent 4fcbf38420
commit a5988034a4
4 changed files with 82 additions and 3 deletions
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3
lld/COFF/Writer.cpp
View File

@ -1953,7 +1953,8 @@ void Writer::writeSections() {
// Fill gaps between functions in .text with INT3 instructions
// instead of leaving as NUL bytes (which can be interpreted as
// ADD instructions).
if (sec->header.Characteristics & IMAGE_SCN_CNT_CODE)
if ((sec->header.Characteristics & IMAGE_SCN_CNT_CODE) &&
(ctx.config.machine == AMD64 || ctx.config.machine == I386))
memset(secBuf, 0xCC, sec->getRawSize());
parallelForEach(sec->chunks, [&](Chunk *c) {
c->writeTo(secBuf + c->getRVA() - sec->getRVA());

2
lld/test/COFF/arm-thumb-thunks-multipass.s
View File

@ -67,4 +67,4 @@ far_func\i:
// FUNC01-THUNKS: 40500a: f2c0 0c10 movt r12, #16
// FUNC01-THUNKS: 40500e: 44e7 add pc, r12
// The instruction below is padding from the .balign
// FUNC01-THUNKS: 405010: cccc ldm r4!, {r2, r3, r6, r7}
// FUNC01-THUNKS: 405010: 0000 movs r0, r0

2
lld/test/COFF/arm64-import2.test
View File

@ -18,7 +18,7 @@
# AFTER: 140001000: 94000004 bl 0x140001010
# AFTER: 140001004: 94000006 bl 0x14000101c
# AFTER: 140001008: d65f03c0 ret
# AFTER: 14000100c: ccccccff <unknown>
# AFTER: 14000100c: 000000ff
# AFTER: 140001010: b0000010 adrp x16, 0x140002000
# AFTER: 140001014: f9403210 ldr x16, [x16, #96]
# AFTER: 140001018: d61f0200 br x16

78
lld/test/COFF/gaps-fill.test Normal file
View File

@ -0,0 +1,78 @@
# REQUIRES: aarch64
# RUN: split-file %s %t.dir
# RUN: llvm-mc -filetype=obj -triple=aarch64-windows %t.dir/arm64-dllmain.s -o %t.dir/arm64-dllmain.obj
# RUN: llvm-mc -filetype=obj -triple=aarch64-windows %t.dir/arm64-p4sym.s -o %t.dir/arm64-p4sym.obj
# RUN: lld-link -dll -machine:arm64 %t.dir/arm64-dllmain.obj %t.dir/arm64-p4sym.obj -out:%t.dll
# RUN: llvm-objdump -dz %t.dll | FileCheck -check-prefix=CHECK-ARM64 %s
# CHECK-ARM64: 180001000: 52800020 mov w0, #0x1
# CHECK-ARM64: 180001004: d65f03c0 ret
# CHECK-ARM64: 180001008: 00000000
# CHECK-ARM64: 18000100c: 00000000
# CHECK-ARM64: 180001010: 52800040 mov w0, #0x2
# CHECK-ARM64: 180001014: d65f03c0 ret
#--- arm64-dllmain.s
.def _DllMainCRTStartup;
.scl 2;
.type 32;
.endef
.globl _DllMainCRTStartup
.p2align 2
_DllMainCRTStartup:
mov w0, #1
ret
#--- arm64-p4sym.s
.def p4sym;
.scl 2;
.type 32;
.endef
.globl p4sym
.p2align 4
p4sym:
mov w0, #2
ret
# RUN: llvm-mc -filetype=obj -triple=x86_64-windows %t.dir/x86_64-dllmain.s -o %t.dir/x86_64-dllmain.obj
# RUN: llvm-mc -filetype=obj -triple=x86_64-windows %t.dir/x86_64-p4sym.s -o %t.dir/x86_64-p4sym.obj
# RUN: lld-link -dll -machine:amd64 %t.dir/x86_64-dllmain.obj %t.dir/x86_64-p4sym.obj -out:%t.dll
# RUN: llvm-objdump -dz %t.dll | FileCheck -check-prefix=CHECK-X64 %s
# CHECK-X64: 180001000: b8 01 00 00 00 movl $0x1, %eax
# CHECK-X64: 180001005: c3 retq
# CHECK-X64: 180001006: cc int3
# CHECK-X64: 180001007: cc int3
# CHECK-X64: 180001008: cc int3
# CHECK-X64: 180001009: cc int3
# CHECK-X64: 18000100a: cc int3
# CHECK-X64: 18000100b: cc int3
# CHECK-X64: 18000100c: cc int3
# CHECK-X64: 18000100d: cc int3
# CHECK-X64: 18000100e: cc int3
# CHECK-X64: 18000100f: cc int3
# CHECK-X64: 180001010: b8 02 00 00 00 movl $0x2, %eax
# CHECK-X64: 180001015: c3 retq
#--- x86_64-dllmain.s
.def _DllMainCRTStartup;
.scl 2;
.type 32;
.endef
.globl _DllMainCRTStartup
.p2align 4, 0x90
_DllMainCRTStartup:
movl $1, %eax
retq
#--- x86_64-p4sym.s
.def p4sym;
.scl 2;
.type 32;
.endef
.globl p4sym
.p2align 4, 0x90
p4sym:
movl $2, %eax
retq