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fix the detail for PC-relative relocations and add explanation #58
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In the BFD code (under review now), we have:
#define RELOCATE_CALC_PC32_HI20(relocation, pc) \
({ \
bfd_vma lo = (relocation) & ((bfd_vma)0xfff); \
pc = pc & (~(bfd_vma)0xfff); \
if (lo > 0x7ff) \
{ \
relocation += 0x1000; \
} \
relocation &= ~(bfd_vma)0xfff; \
relocation -= pc; \
})
#define RELOCATE_CALC_PC64_HI32(relocation, pc) \
({ \
bfd_vma lo = (relocation) & ((bfd_vma)0xfff); \
if (lo > 0x7ff) \
{ \
relocation -= 0x100000000; \
} \
relocation -= (pc & ~(bfd_vma)0xffffffff); \
})
Pay attention at `relocation += 0x1000` and `relocation -= 0x100000000`.
Currently our detailed description does not strictly match it.
This will puzzle the engineer implementing or reviewing the relocs for
other linkers (gold/lld/mold) and cause we criticized by the upstream
reviewers. Fix the pseudo-code in the "detail" column and add two
footnotes as explanation about why the additional operation is needed.
xen0n
approved these changes
Dec 4, 2022
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xen0n
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认同。我自己实现 LLD 时候很是烧了一些脑细胞。。
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In the BFD code (under review now), we have:
Pay attention at
relocation += 0x1000andrelocation -= 0x100000000.Currently our detailed description does not strictly match it.
This will puzzle the engineer implementing or reviewing the relocs for
other linkers (gold/lld/mold) and cause we criticized by the upstream
reviewers. Fix the pseudo-code in the "detail" column and add two
footnotes as explanation about why the additional operation is needed.