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| author | Fangrui Song <maskray@google.com> | 2020-04-30 22:15:05 -0700 |
|---|---|---|
| committer | Fangrui Song <maskray@google.com> | 2020-05-01 14:25:37 -0700 |
| commit | ec786906f5feb4dceba1b5338927079e63e78095 (patch) | |
| tree | e347eae90604daf6437e799795ca22849edcdec0 /llvm/lib/Object/ObjectFile.cpp | |
| parent | 7585ba208e67443d0fbc883db320934c65312b02 (diff) | |
| download | llvm-ec786906f5feb4dceba1b5338927079e63e78095.zip llvm-ec786906f5feb4dceba1b5338927079e63e78095.tar.gz llvm-ec786906f5feb4dceba1b5338927079e63e78095.tar.bz2 | |
[llvm-objcopy] -O binary: skip empty sections
After SHF_ALLOC sections are ordered by LMA:
* If initial sections are empty, GNU objcopy skips their contents while we
emit leading zeros. (binary-paddr.test %t4)
* If trailing sections are empty, GNU objcopy skips their contents while we
emit trailing zeros. (binary-paddr.test %t5)
This patch matches GNU objcopy's behavior. Linkers don't keep p_memsz
PT_LOAD segments. Such empty sections would not have a containing
PT_LOAD and `Section::ParentSegment` might be null if linkers fail to
optimize the file offsets (lld D79254).
In particular, without D79254, the arm Linux kernel's multi_v5_defconfig
depends on this behavior: in `vmlinux`, an empty .text_itcm is mapped at
a very high address (0xfffe0000) but the kernel does not expect
`objcopy -O binary` to create a very large `arch/arm/boot/Image`
(0xfffe0000-0xc0000000 ~= 1GiB). See https://bugs.llvm.org/show_bug.cgi?id=45632
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D79229
Diffstat (limited to 'llvm/lib/Object/ObjectFile.cpp')
0 files changed, 0 insertions, 0 deletions