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[ELF] Allow sections after a non-SHF_ALLOC section to be covered by PT_LOAD

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GNU ld allows sections after a non-SHF_ALLOC section to be covered by PT_LOAD
(PR37607) and assigns addresses to non-SHF_ALLOC output sections (similar to
SHF_ALLOC NOBITS sections. The location counter is not advanced).

This patch tries to fix PR37607 (remove a special case in
`Writer<ELFT>::createPhdrs`). To make the created PT_LOAD meaningful, we cannot
reset dot to 0 for a middle non-SHF_ALLOC output section. This results in
removal of two special cases in LinkerScript::assignOffsets. Non-SHF_ALLOC
non-orphan sections can have non-zero addresses like in GNU ld.

The zero address rule for non-SHF_ALLOC sections is weakened to apply to orphan
only. This results in a special case in createSection and findOrphanPos, respectively.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D85100
This commit is contained in:
Fangrui Song
2020-08-05 09:30:23 -07:00
parent 21b4f8060a
commit 030ddc0a0b
5 changed files with 63 additions and 25 deletions
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7
lld/ELF/LinkerScript.cpp
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@@ -586,6 +586,8 @@ static OutputSection *findByName(ArrayRef<BaseCommand *> vec,
static OutputSection *createSection(InputSectionBase *isec,
StringRef outsecName) {
OutputSection *sec = script->createOutputSection(outsecName, "<internal>");
if (!(isec->flags & SHF_ALLOC))
sec->addrExpr = [] { return 0; };
sec->recordSection(isec);
return sec;
}
@@ -848,9 +850,6 @@ static OutputSection *findFirstSection(PhdrEntry *load) {
// This function assigns offsets to input sections and an output section
// for a single sections command (e.g. ".text { *(.text); }").
void LinkerScript::assignOffsets(OutputSection *sec) {
if (!(sec->flags & SHF_ALLOC))
dot = 0;
const bool sameMemRegion = ctx->memRegion == sec->memRegion;
const bool prevLMARegionIsDefault = ctx->lmaRegion == nullptr;
ctx->memRegion = sec->memRegion;
@@ -858,7 +857,7 @@ void LinkerScript::assignOffsets(OutputSection *sec) {
if (ctx->memRegion)
dot = ctx->memRegion->curPos;
if ((sec->flags & SHF_ALLOC) && sec->addrExpr)
if (sec->addrExpr)
setDot(sec->addrExpr, sec->location, false);
// If the address of the section has been moved forward by an explicit