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[ELF] Change (NOLOAD) section type mismatch error to warning 

Making a (NOLOAD) section SHT_PROGBITS is fishy (the user may expect all-zero
content, but the linker does not check that), but some projects (e.g. Linux
kernel https://github.com/ClangBuiltLinux/linux/issues/1597) traditionally rely
on the behavior. Issue a warning to not break them.
This commit is contained in:
Fangrui Song 2022-02-18 11:20:36 -08:00
parent 1e116867db
commit cb0a4bb5be
2 changed files with 17 additions and 7 deletions
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15
lld/ELF/OutputSections.cpp
View File

@ -112,11 +112,16 @@ void OutputSection::commitSection(InputSection *isec) {
if (hasInputSections || typeIsSet) {
if (typeIsSet || !canMergeToProgbits(type) ||
!canMergeToProgbits(isec->type)) {
errorOrWarn("section type mismatch for " + isec->name + "\n>>> " +
toString(isec) + ": " +
getELFSectionTypeName(config->emachine, isec->type) +
"\n>>> output section " + name + ": " +
getELFSectionTypeName(config->emachine, type));
// Changing the type of a (NOLOAD) section is fishy, but some projects
// (e.g. https://github.com/ClangBuiltLinux/linux/issues/1597)
// traditionally rely on the behavior. Issue a warning to not break
// them. Other types get an error.
auto diagnose = type == SHT_NOBITS ? warn : errorOrWarn;
diagnose("section type mismatch for " + isec->name + "\n>>> " +
toString(isec) + ": " +
getELFSectionTypeName(config->emachine, isec->type) +
"\n>>> output section " + name + ": " +
getELFSectionTypeName(config->emachine, type));
}
type = SHT_PROGBITS;
} else {

9
lld/test/ELF/linkerscript/noload.s
View File

@ -17,9 +17,14 @@
# CHECK: 00 .data_noload_a .data_noload_b .no_input_sec_noload {{$}}
# CHECK: 01 .text {{$}}
# RUN: not ld.lld --script %t/lds %t.o %t/mismatch.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
## The output SHT_PROBITS is contrary to the user expectation of SHT_NOBITS.
## Issue a warning. See https://github.com/ClangBuiltLinux/linux/issues/1597
# RUN: ld.lld --script %t/lds %t.o %t/mismatch.o -o %t/out 2>&1 |& FileCheck %s --check-prefix=WARN
# RUN: llvm-readelf -S -l %t/out | FileCheck %s --check-prefix=CHECK2
# ERR: error: section type mismatch for .data_noload_a
# WARN: warning: section type mismatch for .data_noload_a
# CHECK2: Name Type Address Off Size
# CHECK2: .data_noload_a PROGBITS 0000000000000000 [[OFF:[0-9a-f]+]] 001001
#--- asm
.section .text,"ax",@progbits