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authorRich Felker <dalias@aerifal.cx>2020-03-11 18:43:11 -0400
committerRich Felker <dalias@aerifal.cx>2020-03-14 21:21:45 -0400
commit5053fd2644c188ac6531e5fe6a52a1a6d0df2fc2 (patch)
tree16c93914d9254fc214e0df87f37684b26ca970d1 /arch/mips/syscall_arch.h
parent2f2348c9588d61680123bbe438db38acf5dfea4c (diff)
downloadmusl-5053fd2644c188ac6531e5fe6a52a1a6d0df2fc2.tar.gz
revert mips64/n32 syscall asm clean-up due to regressions
effectivly revert commit ddc7c4f936c7a90781072f10dbaa122007e939d0 which was wrong; it caused a major regression on Linux versions prior to 2.6.36. old kernels did not properly preserve r2 across syscall restart, and instead restarted with the instruction right before syscall, imposing a contract that the previous instruction must load r2 from an immediate or a register (or memory) not clobbered by the syscall. since other changes were made since, including removal of the struct stat conversion that was replaced by separate struct kstat, this is not a direct revert, only a functional one. the "0"(r2) input constraint added back seems useless/erroneous, but without it most gcc versions (seems to be all prior to 9.x) fail to honor the output register binding for r2. this seems to be a variant of gcc bug #87733. further changes should be made later if a better workaround is found, but this one has been working since 2012. it seems this issue was encountered but misidentified then, when it inspired commit 4221f154ff29ab0d6be1e7beaa5ea2d1731bc58e.
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