From d605f414dba6490b03029ec8a07ff5bec4ac4fa1 Mon Sep 17 00:00:00 2001 From: George Rimar Date: Thu, 26 Oct 2017 09:13:19 +0000 Subject: [PATCH] =?UTF-8?q?[ELF]=20-=20Dedupli=D1=81ate=20FDEs=20when=20se?= =?UTF-8?q?ctions=20are=20ICFed.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When LLD do ICF for 2 identical sections it leaves 2 duplicate entries in .eh_frame pointing to the same address. After that it fixes .eh_frame_header's header, so that it says it contains single FDE, though section itself contains 2 (it contains garbage data at tail). As a result excessive entries in .eh_frame and excessive dummy data in .eh_frame_header emited to output. Patch fixes that. This is PR34518. Differential revision: https://reviews.llvm.org/D38998 llvm-svn: 316648 --- lld/ELF/SyntheticSections.cpp | 6 +- lld/test/ELF/eh-frame-hdr-icf-fde.s | 95 +++++++++++++++++++++++++++++ lld/test/ELF/eh-frame-hdr-icf.s | 15 ++--- 3 files changed, 107 insertions(+), 9 deletions(-) create mode 100644 lld/test/ELF/eh-frame-hdr-icf-fde.s diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp index bd3549ae3073..a6bf9f9b498a 100644 --- a/lld/ELF/SyntheticSections.cpp +++ b/lld/ELF/SyntheticSections.cpp @@ -449,9 +449,11 @@ bool EhFrameSection::isFdeLive(EhSectionPiece &Fde, const RelTy &Rel = Rels[FirstRelI]; SymbolBody &B = Sec->template getFile()->getRelocTargetSym(Rel); + + // FDEs for garbage-collected or merged-by-ICF sections are dead. if (auto *D = dyn_cast(&B)) - if (D->Section) - return cast(D->Section)->Repl->Live; + if (auto *Sec = cast_or_null(D->Section)) + return Sec->Live && (Sec == Sec->Repl); return false; } diff --git a/lld/test/ELF/eh-frame-hdr-icf-fde.s b/lld/test/ELF/eh-frame-hdr-icf-fde.s new file mode 100644 index 000000000000..54c2cd8bf8c9 --- /dev/null +++ b/lld/test/ELF/eh-frame-hdr-icf-fde.s @@ -0,0 +1,95 @@ +# REQUIRES: x86 + +## Testcase checks that we correctly deduplicate FDEs when ICF +## merges two sections. + +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t +# RUN: ld.lld %t -o %t2 --icf=all --eh-frame-hdr +# RUN: llvm-readobj -r %t | FileCheck %s --check-prefix=OBJ +# RUN: llvm-readobj -s -section-data %t2 | FileCheck %s + +# OBJ: Relocations [ +# OBJ-NEXT: Section {{.*}} .rela.eh_frame { +# OBJ-NEXT: 0x20 R_X86_64_PC32 .text.f1 0x0 +# OBJ-NEXT: 0x34 R_X86_64_PC32 .text.f1 0x2 +# OBJ-NEXT: 0x48 R_X86_64_PC32 .text.f2 0x0 +# OBJ-NEXT: 0x5C R_X86_64_PC32 .text.f2 0x2 +# OBJ-NEXT: } +# OBJ-NEXT: ] + +# CHECK: Section { +# CHECK: Index: 1 +# CHECK: Name: .eh_frame_hdr +# CHECK-NEXT: Type: SHT_PROGBITS +# CHECK-NEXT: Flags [ +# CHECK-NEXT: SHF_ALLOC +# CHECK-NEXT: ] +# CHECK-NEXT: Address: 0x200158 +# CHECK-NEXT: Offset: 0x158 +# CHECK-NEXT: Size: 28 +# CHECK-NEXT: Link: 0 +# CHECK-NEXT: Info: 0 +# CHECK-NEXT: AddressAlignment: +# CHECK-NEXT: EntrySize: 0 +# CHECK-NEXT: SectionData ( +# CHECK-NEXT: 0000: 011B033B 1C000000 02000000 A80E0000 +## ^ ^-- FDE(1) PC +## ^-- Number of FDEs +# CHECK-NEXT: 0010: 38000000 AA0E0000 50000000 +## ^-- FDE(2) PC +# CHECK-NEXT: ) +# CHECK-NEXT: } +## FDE(1) == 0x201000 - .eh_frame_hdr(0x200158) = 0xEA8 +## FDE(2) == 0x201000 - .eh_frame_hdr(0x200158) + 2(relocation addend) = 0xEAA + +## Check .eh_frame contains CIE and two FDEs remaining after ICF. +# CHECK-NEXT: Section { +# CHECK-NEXT: Index: 2 +# CHECK-NEXT: Name: .eh_frame +# CHECK-NEXT: Type: SHT_PROGBITS +# CHECK-NEXT: Flags [ +# CHECK-NEXT: SHF_ALLOC +# CHECK-NEXT: ] +# CHECK-NEXT: Address: 0x200178 +# CHECK-NEXT: Offset: 0x178 +# CHECK-NEXT: Size: 72 +# CHECK-NEXT: Link: 0 +# CHECK-NEXT: Info: 0 +# CHECK-NEXT: AddressAlignment: 8 +# CHECK-NEXT: EntrySize: 0 +# CHECK-NEXT: SectionData ( +# CHECK-NEXT: 0000: 14000000 00000000 017A5200 01781001 +# CHECK-NEXT: 0010: 1B0C0708 90010000 14000000 1C000000 +# CHECK-NEXT: 0020: 680E0000 01000000 00000000 00000000 +# CHECK-NEXT: 0030: 14000000 34000000 520E0000 01000000 +# CHECK-NEXT: 0040: 00000000 00000000 +# CHECK-NEXT: ) +# CHECK-NEXT: } + +# CHECK: Section { +# CHECK: Index: +# CHECK: Name: .text +# CHECK-NEXT: Type: SHT_PROGBITS +# CHECK-NEXT: Flags [ +# CHECK-NEXT: SHF_ALLOC +# CHECK-NEXT: SHF_EXECINSTR +# CHECK-NEXT: ] +# CHECK-NEXT: Address: 0x201000 + +.section .text.f1, "ax" +.cfi_startproc +nop +.cfi_endproc +nop +.cfi_startproc +ret +.cfi_endproc + +.section .text.f2, "ax" +.cfi_startproc +nop +.cfi_endproc +nop +.cfi_startproc +ret +.cfi_endproc diff --git a/lld/test/ELF/eh-frame-hdr-icf.s b/lld/test/ELF/eh-frame-hdr-icf.s index 1b42285f5d32..0ef3f97de8d3 100644 --- a/lld/test/ELF/eh-frame-hdr-icf.s +++ b/lld/test/ELF/eh-frame-hdr-icf.s @@ -2,17 +2,18 @@ # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t # RUN: ld.lld %t -o %t2 --icf=all --eh-frame-hdr -# RUN: llvm-objdump -s %t2 | FileCheck %s +# RUN: llvm-objdump -s -section-headers %t2 | FileCheck %s + +## Check .eh_frame_hdr contains single FDE and no garbage data at tail. +# CHECK: Sections: +# CHECK: Idx Name Size +# CHECK: .eh_frame_hdr 00000014 # CHECK: Contents of section .eh_frame_hdr: -# CHECK-NEXT: 200158 011b033b 1c000000 01000000 a80e0000 +# CHECK-NEXT: 200158 011b033b 14000000 01000000 # ^ FDE count -# CHECK-NEXT: 200168 38000000 00000000 00000000 -# ^ FDE for f2 -.globl _start, f1, f2 -_start: - ret +.globl f1, f2 .section .text.f1, "ax" f1: