std.os.linux.start_pie: Add mips and powerpc support
#20823
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alexrp
commented
Jul 27, 2024
| .mips64, .mips64el => asm volatile ( | ||
| \\ .weak _DYNAMIC | ||
| \\ .hidden _DYNAMIC | ||
| \\ .balign 8 |
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On MIPS, this call will require a relocation, which we can't do until after PIE relocations have been applied.
…ibcalls.
The code would cause LLVM to emit a jump table for the switch in the loop over
the dynamic tags. That jump table was far enough away that the compiler decided
to go through the GOT, which would of course break at this early stage as we
haven't applied MIPS's local GOT relocations yet, nor can we until we've walked
through the _DYNAMIC array.
The first attempt at rewriting this used code like this:
var sorted_dynv = [_]elf.Addr{0} ** elf.DT_NUM;
But this is also problematic as it results in a memcpy() call. Instead, we
explicitly initialize it to undefined and use a loop of volatile stores to
clear it.
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cc @kubkon you might want to check the relocation stuff? |
kubkon
requested changes
Jul 30, 2024
Not likely to be necessary ever, but might as well be 100% correct.
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kubkon
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Jul 30, 2024
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Nice! |
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Requires #20822 to actually work.