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[ELF] Support high address DW_EH_sdata4 for ELFCLASS32

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When the address pointer encoding in FDEs uses
DW_EH_PE_absptr|DW_EH_PE_sdata4, the address is sign-extended to 64-bit
by `readFdeAddr`. We should truncate the address to 32-bit for
ELFCLASS32. Otherwise, `isInt<32>(pc - va)` could be false, leading to a
spurious error in `getFdeData`.

In LLVM, this appears a MIPS-specific issue.
Fix #88852

Pull Request: https://github.com/llvm/llvm-project/pull/92438
This commit is contained in:
Fangrui Song 2024-05-20 00:13:09 -07:00 committed by GitHub
parent 073488cb1f
commit dd8cb3d4f1
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2 changed files with 10 additions and 1 deletions
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2
lld/ELF/SyntheticSections.cpp
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@ -613,7 +613,7 @@ uint64_t EhFrameSection::getFdePc(uint8_t *buf, size_t fdeOff,
size_t off = fdeOff + 8;
uint64_t addr = readFdeAddr(buf + off, enc & 0xf);
if ((enc & 0x70) == DW_EH_PE_absptr)
return addr;
return config->is64 ? addr : uint32_t(addr);
if ((enc & 0x70) == DW_EH_PE_pcrel)
return addr + getParent()->addr + off + outSecOff;
fatal("unknown FDE size relative encoding");

9
lld/test/ELF/mips-eh_frame-pic.s
View File

@ -27,6 +27,11 @@
## relative addressing.
# NOPIC32-ERR: ld.lld: error: relocation R_MIPS_32 cannot be used against local symbol
## https://github.com/llvm/llvm-project/issues/88852: getFdePc should return a
## 32-bit address.
# RUN: ld.lld --eh-frame-hdr -Ttext=0x80000000 %t-nopic32.o -o %t-nopic32
# RUN: llvm-readelf -x .eh_frame_hdr %t-nopic32 | FileCheck %s --check-prefix=NOPIC32-HDR
## For -fPIC, .eh_frame should contain DW_EH_PE_pcrel | DW_EH_PE_sdata4 values:
# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux --position-independent %s -o %t-pic32.o
# RUN: llvm-readobj -r %t-pic32.o | FileCheck %s --check-prefixes=RELOCS,PIC32-RELOCS
@ -51,6 +56,10 @@
## Note: ld.bfd converts the R_MIPS_64 relocs to DW_EH_PE_pcrel | DW_EH_PE_sdata8
## for N64 ABI (and DW_EH_PE_pcrel | DW_EH_PE_sdata4 for MIPS32)
# NOPIC32-HDR: Hex dump of section '.eh_frame_hdr':
# NOPIC32-HDR: 0x80010038 011b033b 00000010 00000001 fffeffc8 .
# NOPIC32-HDR: 0x80010048 00000028 .
.ent func
.global func
func: