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Work around Rosetta clobbering startup registers on M1 Macs (issue #429) (#453)

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Rosetta doesn't correctly respect the startup registers as defined in LC_UNIXTHREAD
which makes platform detection go awry. But at least Rosetta appears to consistently
set rbx to 0x00000000ffffffff and rdx to 0x0000000000000001 at startup for every
x64 executable I could get my hands on. So we use that to detect Rosetta's presence
and set up the correct registers for XNU.
This commit is contained in:
Daniil Kulchenko 2022-06-27 16:28:59 -07:00 • committed by GitHub
parent 5297897ba1
commit 9f8e6c10dd
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4 changed files with 38 additions and 4 deletions
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13
ape/loader-macho.S
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@ -113,7 +113,18 @@ macho: .long 0xFEEDFACE+1
.endobj macho,globl
.align 64
_start: mov %rsp,%rsi
_start:
// Hack for detecting M1 Rosetta environment.
// https://github.com/jart/cosmopolitan/issues/429#issuecomment-1166704377
cmp $-1,%ebx
jne 0f
cmp $+1,%edx
jne 0f
mov $XNU,%dl
xor %ecx,%ecx
0: mov %rsp,%rsi
jmp ApeLoader
.endfn _start,globl