Pull in r369828 from upstream lld trunk (by Fāng-ruì Sòng):
[ELF] Align the first section of a PT_LOAD even if its type is SHT_NOBITS Reported at https://reviews.llvm.org/D64930#1642223 If the only section of a PT_LOAD is a SHT_NOBITS section (e.g. .bss), we may not align its sh_offset. p_offset of the PT_LOAD will be set to sh_offset, and we will get p_offset!=p_vaddr (mod p_align). If such executable is mapped by the Linux kernel, it will segfault. After D64906, this may happen the non-linker script case. The linker script case has had this issue for a long time. This was fixed by rL321657 (but the test linkerscript/nobits-offset.s failed to test a SHT_NOBITS section), but broken by rL345154. Reviewed By: peter.smith Differential Revision: https://reviews.llvm.org/D66658 Pull in r371013 from upstream lld trunk (by Rui Ueyama): Align output segments correctly Previously, segments were aligned according to their first section's alignment requirements. That was not correct, but segments are also aligned to a page boundary, and a page boundary is usually much larger than a section alignment requirement, so no one noticed this bug before. Now, lld has --nmagic option which sets maxPageSize to 1 to effectively disable page alignment, which reveals the issue. Fixes https://bugs.llvm.org/show_bug.cgi?id=43212 Differential Revision: https://reviews.llvm.org/D67152 Together, these should ensure gpboot.out gets a correctly aligned offset for its .rodata section, and fix "layout constraint violation" errors from objcopy.
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2020-12-20 02:59:44 +00:00
svn path=/projects/clang900-import/; revision=351879
@ -2230,25 +2230,27 @@ template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
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// same with its virtual address modulo the page size, so that the loader can
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// load executables without any address adjustment.
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static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {
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// File offsets are not significant for .bss sections. By convention, we keep
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// section offsets monotonically increasing rather than setting to zero.
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if (os->type == SHT_NOBITS)
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return off;
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// The first section in a PT_LOAD has to have congruent offset and address
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// module the page size.
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if (os->ptLoad && os->ptLoad->firstSec == os) {
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uint64_t alignment =
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std::max<uint64_t>(os->ptLoad->p_align, config->maxPageSize);
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return alignTo(off, alignment, os->addr);
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}
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// File offsets are not significant for .bss sections other than the first one
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// in a PT_LOAD. By convention, we keep section offsets monotonically
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// increasing rather than setting to zero.
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if (os->type == SHT_NOBITS)
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return off;
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// If the section is not in a PT_LOAD, we just have to align it.
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if (!os->ptLoad)
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return alignTo(off, os->alignment);
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// The first section in a PT_LOAD has to have congruent offset and address
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// module the page size.
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OutputSection *first = os->ptLoad->firstSec;
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if (os == first) {
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uint64_t alignment = std::max<uint64_t>(os->alignment, config->maxPageSize);
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return alignTo(off, alignment, os->addr);
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}
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// If two sections share the same PT_LOAD the file offset is calculated
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// using this formula: Off2 = Off1 + (VA2 - VA1).
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OutputSection *first = os->ptLoad->firstSec;
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return first->offset + os->addr - first->addr;
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}
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