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https://github.com/jart/cosmopolitan.git
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f94c11d978
The ape loader now passes the program executable name directly as a register. `x2` is used on aarch64, `%rdx` on x86_64. This is passed as the third argument to `cosmo()` (M1) or `Launch` (non-M1) and is assigned to the global `__program_executable_name`. `GetProgramExecutableName` now returns this global's value, setting it if it is initially null. `InitProgramExecutableName` first tries exotic, secure methods: `KERN_PROC_PATHNAME` on FreeBSD/NetBSD, and `/proc` on Linux. If those produce a reasonable response (i.e., not `"/usr/bin/ape"`, which happens with the loader before this change), that is used. Otherwise, if `issetugid()`, the empty string is used. Otherwise, the old argv/envp parsing code is run. The value returned from the loader is always the full absolute path of the binary to be executed, having passed through `realpath`. For the non-M1 loader, this necessitated writing `RealPath`, which uses `readlinkat` of `"/proc/self/fd/[progfd]"` on Linux, `F_GETPATH` on Xnu, and the `__realpath` syscall on OpenBSD. On FreeBSD/NetBSD, it punts to `GetProgramExecutableName`, which is secure on those OSes. With the loader, all platforms now have a secure program executable name. With no loader or an old loader, everything still works as it did, but setuid/setgid is not supported if the insecure pathfinding code would have been needed. Fixes #991.
92 lines
3.1 KiB
ArmAsm
92 lines
3.1 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│ vi: set noet ft=asm ts=8 sw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2023 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.internal.h"
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// Calls _start() function of loaded program.
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//
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// When the program entrypoint is called, all registers shall be
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// cleared, with the exception of (1) %rdi will be equal to %rsp
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// on FreeBSD and (2) %cl will contain the detected host OS code
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//
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// We clear all the general registers we can to have some wiggle
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// room, to extend the behavior of this loader in the future. We
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// don't need to clear the XMM registers because your APE loader
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// should be compiled using gcc/clang's -mgeneral-regs-only flag
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//
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// @param rdi is passed through as-is
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// @param rsi is address of entrypoint (becomes zero)
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// @param rdx is passed through as-is
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// @param rcx is stack pointer (becomes r8)
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// @noreturn
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Launch:
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#ifdef __aarch64__
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mov x16,x1
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mov sp,x3
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mov x1,0
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mov x3,x4
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mov x4,0
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mov x5,0
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mov x6,0
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mov x7,0
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mov x8,0
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mov x9,0
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mov x10,0
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mov x11,0
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mov x12,0
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mov x13,0
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mov x14,0
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mov x15,0
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mov x17,0
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mov x19,0
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mov x20,0
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mov x21,0
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mov x22,0
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mov x23,0
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mov x24,0
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mov x25,0
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mov x26,0
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mov x27,0
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mov x28,0
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mov x29,0
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mov x30,0
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br x16
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#else
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mov %rcx,%rsp
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mov %r8,%rcx
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xor %r8d,%r8d
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xor %r9d,%r9d
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xor %r10d,%r10d
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xor %r11d,%r11d
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xor %r12d,%r12d
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xor %r13d,%r13d
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xor %r14d,%r14d
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xor %r15d,%r15d
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push %rsi
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xor %esi,%esi
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xor %ebp,%ebp
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xor %ebx,%ebx
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xor %eax,%eax
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ret
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#endif
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.endfn Launch,globl
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