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Loaders rewrite argv[0] for old binaries (#1170)

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For this to work, a loader has to be able to tell the difference between
an ‘old’ and a ‘new’ binary. This is achieved via a repurposing of ELF’s
e_flags field. We previously tried to use the padding in e_ident for it,
but binutils was resetting it to zero in e.g. strip.

This introduces one new ELF flag for cosmopolitan binaries. It is called
`EF_APE_MODERN`. We choose 0x101ca75, "lol cat 5".

It should now be safe to install the ape loader binfmt registration with
the `P` flag.
This commit is contained in:
Jōshin 2024-05-07 17:42:18 -07:00 • committed by GitHub
parent 57c0b065c8
commit 7d31fc311a
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5 changed files with 27 additions and 3 deletions
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ape/ape.S
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@ -196,7 +196,7 @@ ape_mz:
.quad ape_elf_entry // 18: e_entry
.quad ape_elf_phoff // 20: e_phoff
.quad ape_elf_shoff // 28: e_shoff
.long 0 // 30: e_flags
.long 0x101ca75 // 30: ape e_flags
.short 64 // 34: e_ehsize
.short 56 // 36: e_phentsize
.short ape_elf_phnum // 38: e_phnum
@ -669,7 +669,7 @@ apesh: .ascii "\n@\n#'\"\n" // sixth edition shebang
.shstub ape_elf_entry,8 // 18: e_entry
.shstub ape_elf_phoff,8 // 20: e_phoff
.shstub ape_elf_shoff,8 // 28: e_shoff
.ascii "\\0\\0\\0\\0" // 30: e_flags
.ascii "\\165\\312\\1\\1" // 30: ape e_flags
.ascii "\\100\\0" // 34: e_ehsize
.ascii "\\070\\0" // 36: e_phentsize
.shstub ape_elf_phnum,2 // 38: e_phnum