This is an archive of the discontinued LLVM Phabricator instance.

Differential D93954

ELF: Teach the linker about the 'B' augmentation string character.
ClosedPublic

Authored by pcc on Dec 30 2020, 11:10 PM.

Details

Reviewers
MaskRay
psmith
• espindola
Commits
rGaed84542d5a0: ELF: Teach the linker about the 'B' augmentation string character.
Summary

This character indicates that when return pointer authentication is
being used, the function signs the return address using the B key.

Diff Detail

Event Timeline

pcc created this revision.Dec 30 2020, 11:10 PM
Herald added a reviewer: • espindola. · View Herald TranscriptDec 30 2020, 11:10 PM
Herald added subscribers: arichardson, emaste. · View Herald Transcript
pcc requested review of this revision.Dec 30 2020, 11:10 PM
Herald added a project: Restricted Project. · View Herald TranscriptDec 30 2020, 11:10 PM
Harbormaster completed remote builds in B83778: Diff 314172.Dec 30 2020, 11:37 PM
MaskRay added inline comments.Dec 31 2020, 12:47 AM
lld/test/ELF/cfi-b-key-frame.s
1 ↗(On Diff #314172)

Such tests are named eh-frame-*

pcc updated this revision to Diff 314759.Jan 5 2021, 5:25 PM
  • Rename test
MaskRay accepted this revision.Jan 5 2021, 5:51 PM
MaskRay added inline comments.
lld/ELF/EhFrame.cpp
197

Because 'R' triggers an early return, so we don't error for "zRB"... --icf= triggers hasLSDA

This revision is now accepted and ready to land.Jan 5 2021, 5:51 PM
Harbormaster completed remote builds in B84142: Diff 314759.Jan 5 2021, 6:08 PM
Closed by commit rGaed84542d5a0: ELF: Teach the linker about the 'B' augmentation string character. (authored by pcc). · Explain WhyJan 5 2021, 7:51 PM
This revision was automatically updated to reflect the committed changes.
pcc added a commit: rGaed84542d5a0: ELF: Teach the linker about the 'B' augmentation string character..

Revision Contents

PathSize
lld/
ELF/
4 lines
test/
ELF/
9 lines

Diff 314786

lld/ELF/EhFrame.cpp

Show First 20 Lines • Show All 188 Lines • ▼ Show 20 Lines for (char c : aug) {
if (c == 'R') if (c == 'R')
return readByte(); return readByte();
if (c == 'z') if (c == 'z')
skipLeb128(); skipLeb128();
else if (c == 'L') else if (c == 'L')
readByte(); readByte();
else if (c == 'P') else if (c == 'P')
skipAugP(); skipAugP();
else if (c != 'S') else if (c != 'B' && c != 'S')
MaskRayUnsubmitted
Not Done
ReplyInline Actions

Because 'R' triggers an early return, so we don't error for "zRB"... --icf= triggers hasLSDA

MaskRay: Because 'R' triggers an early return, so we don't error for "zRB"... --icf= triggers hasLSDA
failOn(aug.data(), "unknown .eh_frame augmentation string: " + aug); failOn(aug.data(), "unknown .eh_frame augmentation string: " + aug);
} }
return DW_EH_PE_absptr; return DW_EH_PE_absptr;
} }
bool EhReader::hasLSDA() { bool EhReader::hasLSDA() {
StringRef aug = getAugmentation(); StringRef aug = getAugmentation();
for (char c : aug) { for (char c : aug) {
if (c == 'L') if (c == 'L')
return true; return true;
if (c == 'z') if (c == 'z')
skipLeb128(); skipLeb128();
else if (c == 'P') else if (c == 'P')
skipAugP(); skipAugP();
else if (c == 'R') else if (c == 'R')
readByte(); readByte();
else if (c != 'S') else if (c != 'B' && c != 'S')
failOn(aug.data(), "unknown .eh_frame augmentation string: " + aug); failOn(aug.data(), "unknown .eh_frame augmentation string: " + aug);
} }
return false; return false;
} }

lld/test/ELF/eh-frame-cfi-b-key.s

  • This file was added.
// REQUIRES: aarch64
// RUN: llvm-mc -filetype=obj -triple aarch64-arm-none-eabi %s -o %t.o
// RUN: ld.lld %t.o -o %t --icf=all --eh-frame-hdr
.globl _start
_start:
.cfi_startproc
.cfi_b_key_frame
.cfi_endproc