Commit 08de6a4a authored by Rui Ueyama's avatar Rui Ueyama
Browse files

Merging r312706: 

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r312706 | anng | 2017-09-07 01:43:56 -0700 (Thu, 07 Sep 2017) | 14 lines

[LLD] Fix padding of .eh_frame when in executable segment

The default padding for an executable segment is the target trap
instruction which for x86_64 is 0xCC. However, the .eh_frame section
requires the padding to be zero. The code that writes the .eh_frame
section assumes that its segment is zero initialized and does not
explicitly write the zero padding. This does not work when the .eh_frame
section is in the executable segment (for example when using
-no-rosegment).

This patch changes the .eh_frame writing code to explicitly write the
zero padding.

Differential Revision: https://reviews.llvm.org/D37462
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llvm-svn: 314861
parent a4fcc49a

lld/ELF/SyntheticSections.cpp

+6 −1
Original line number Diff line number Diff line
@@ -523,9 +523,14 @@ template <class ELFT> 
static void writeCieFde(uint8_t *Buf, ArrayRef<uint8_t> D) {

  memcpy(Buf, D.data(), D.size());



  size_t Aligned = alignTo(D.size(), sizeof(typename ELFT::uint));



  // Zero-clear trailing padding if it exists.

  memset(Buf + D.size(), 0, Aligned - D.size());



  // Fix the size field. -4 since size does not include the size field itself.

  const endianness E = ELFT::TargetEndianness;

  write32<E>(Buf, alignTo(D.size(), sizeof(typename ELFT::uint)) - 4);

  write32<E>(Buf, Aligned - 4);

}



template <class ELFT> void EhFrameSection<ELFT>::finalizeContents() {

lld/test/ELF/eh-frame-padding-no-rosegment.s

0 → 100644
+64 −0
Original line number Diff line number Diff line 
// REQUIRES: x86



.cfi_startproc

.cfi_personality 0x1b, bar

.cfi_endproc



.global bar

.hidden bar

bar:



// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o



// Check the size of the CIE (0x18 + 4) and FDE (0x10 + 4)

// RUN: llvm-readobj -s -section-data %t.o | FileCheck --check-prefix=OBJ %s



// OBJ:      Name: .eh_frame

// OBJ-NEXT: Type:

// OBJ-NEXT: Flags [

// OBJ-NEXT:   SHF_ALLOC

// OBJ-NEXT: ]

// OBJ-NEXT: Address:

// OBJ-NEXT: Offset:

// OBJ-NEXT: Size:

// OBJ-NEXT: Link:

// OBJ-NEXT: Info:

// OBJ-NEXT: AddressAlignment:

// OBJ-NEXT: EntrySize:

// OBJ-NEXT: SectionData (

// OBJ-NEXT:   0000: 18000000 00000000 017A5052 00017810

// OBJ-NEXT:   0010: 061B0000 00001B0C 07089001 10000000

// OBJ-NEXT:   0020: 20000000 00000000 00000000 00000000

// OBJ-NEXT: )



// RUN: ld.lld %t.o -no-rosegment -o %t -shared



// Check that .eh_frame is in the same segment as .text

// RUN: llvm-readobj -l --elf-output-style=GNU %t | FileCheck --check-prefix=PHDR %s



// PHDR: Segment Sections

// PHDR: .text

// PHDR-SAME: .eh_frame



// Check that the CIE and FDE are padded with 0x00 and not 0xCC when the

// .eh_frame section is placed in the executable segment

// RUN: llvm-readobj -s -section-data %t | FileCheck %s



// CHECK:      Name: .eh_frame

// CHECK-NEXT: Type:

// CHECK-NEXT: Flags

// CHECK-NEXT:   SHF_ALLOC

// CHECK-NEXT: ]

// CHECK-NEXT: Address:

// CHECK-NEXT: Offset:

// CHECK-NEXT: Size:

// CHECK-NEXT: Link:

// CHECK-NEXT: Info:

// CHECK-NEXT: AddressAlignment:

// CHECK-NEXT: EntrySize:

// CHECK-NEXT: SectionData (

// CHECK-NEXT:   0000: 1C000000 00000000 017A5052 00017810

// CHECK-NEXT:   0010: 061BBEFF FFFF1B0C 07089001 00000000

// CHECK-NEXT:   0020: 14000000 24000000 A8FFFFFF 00000000

// CHECK-NEXT:   0030: 00000000 00000000

// CHECK-NEXT: )