Fix MIPS __start linker error with default relocation model#171
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walruscraft wants to merge 1 commit intosunfishcode:mainfrom
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Fix MIPS __start linker error with default relocation model#171walruscraft wants to merge 1 commit intosunfishcode:mainfrom
walruscraft wants to merge 1 commit intosunfishcode:mainfrom
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Turns out `la $t9, {entry}` generates a CALL16 relocation in PIC
mode, and CALL16 needs the target to be a global symbol. Since
`entry` is pub(super), the linker rightfully complains. Swapped
to lui/addiu which use HI16/LO16 and don't care about visibility.
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Embarrassing follow-up to #170 - I introduced a bug in the MIPS startup code.
The
la $t9, {entry}instruction in__startgenerates a CALL16 relocation when compiled with PIC (which is the default relocation model formipsel-unknown-linux-gnu). CALL16 requires the target to be a global symbol, butentryispub(super)so the linker rejects it:I missed this because my test setup happened to use
-C relocation-model=static, which avoids PIC entirely. So it linked fine on my end and I never saw the issue. Anyone using the default relocation model would hit this on their first MIPS build.The fix is to use
lui/addiuinstead ofla. These generate HI16/LO16 relocations which work with local symbols. Still loads the address into$t9for PIC convention, just without going through the GOT.Tested by building a real application (kv) for
mipsel-unknown-linux-gnuwithout the relocation-model workaround. Links and runs correctly under QEMU.Sorry about the mess.