[JITLink][MachO] Fix handling of non-extern UNSIGNED pair of SUBTRACT… #1513
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…OR relocs. When processing a MachO SUBTRACTOR/UNSIGNED pair, if the UNSIGNED target is non-extern then check the r_symbolnum field of the relocation to find the targeted section and use the section's address to find 'ToSymbol'. Previously 'ToSymbol' was found by loading the initial value stored at the fixup location and treating this as an address to search for. This is incorrect, however: the initial value includes the addend and will point to the wrong block if the addend is less than zero or greater than the block size. rdar://65756694
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@swift-ci please test |
lgerbarg
approved these changes
Jul 20, 2020
| # | ||
| # jitlink-check: *{8}anon_minuend_quad1 = section_addr(macho_reloc.o, __data) - anon_minuend_quad1 + 2 | ||
| # jitlink-check: *{8}anon_minuend_quad1 = section_addr(macho_reloc.o, __data) - anon_minuend_quad1 - 2 | ||
| # Only the form "B: .quad LA - B + C" is tested. The form "B: .quad B - LA + C" is |
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Should this comment be "B: .quad B - LA - C" (or do you want to keep the addition as the canonical form of the relocation with the understanding C C is negative?"
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Yep -- that expression is referencing the canonical form, though that's less clear now that the example has a negative addend. I'll fix that comment on the mainline to clarify.
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…OR relocs.
When processing a MachO SUBTRACTOR/UNSIGNED pair, if the UNSIGNED target
is non-extern then check the r_symbolnum field of the relocation to find
the targeted section and use the section's address to find 'ToSymbol'.
Previously 'ToSymbol' was found by loading the initial value stored at
the fixup location and treating this as an address to search for. This
is incorrect, however: the initial value includes the addend and will
point to the wrong block if the addend is less than zero or greater than
the block size.
rdar://problem/65756694