Remove realpath/getcwd from loaders #1024
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Noticed a bug in the process, pathlen is out of step with n
(Do not merge without GetProgramExecutableName change)
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TryPath with com==1 tries both non-com and com, so the checks were redundant. With com==0, there is no reason to copy to the buffer if the initial access fails.
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Merges branches 'm1-realpath', 'loader-realpath' and 'getprogramexecutablename-realpath' into no-realpath
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The loader implementing it was never minted, so it seems reasonable not to keep support for it indefinitely. But it seems impolite to break the prerelease loaders people may have been using between releases.
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If we got __program_executable_name, it means the /proc-esque methods are going to return the path of the loader rather than the path of the binary, so do not use them in this case. If the passed path is absolute, use it as-is. Otherwise, copy it into the buffer with getcwd prepended. The sys_faccessat call should be redundant; if TryPath fails, it probably failed because getcwd() was too long, so just use the relative path and accept that chdir will break things. On that note, TryPath now fails prior to the sys_faccessat if getcwd() is too long, and otherwise behaves the way the code used to. The version I wrote before this change would have always succeeded on a truncated path assuming the relative path could have been accessed. The original version would have succeeded on a truncated path if there happened to be a file at that path that could be accessed. This change also backs out the setugid loader check for /dev/fd path. For now, we fail open; if for some reason we are invoked set-id by the loader, we just assume that the user knows what they are doing and do not attempt to second-guess them, beyond politely declining to trust argv[0] or the environment.
jart
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Returns to passing os as `%rcx`, stack pointer as `%rdx` as it was before jart#1024. exe is now passed as `%r8`, and is moved to `%rdx`. os is passed on aarch64, from both loader.c and ape-m1.c. It is currently unused.
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This implements proposals 1 and 2a from this gist:
https://gist.github.com/mrdomino/2222cab61715fd527e82e036ba4156b1
The only reason to use realpath from the loader was to try to prevent a
TOCTOU between the loader and the binary. But this is only a real issue
in set-id contexts, and in those cases there is already a canonical way
to do it:
/dev/fd, passed by the kernel to the loader, so all we haveto do is pass that along to the binary.
Aside from realpath, there is no reason to absolutize the path we supply
to the binary, since it can call
getcwdas well as we can, and on non-M1 the binary is in a much better position to make that call.
Since we no longer absolutize the path, the binary does need to do this,
so we make its argv-parsing code generic and apply that to the different
possible places the path could come from. This means that
_is finallyusable as a relative path, as a nice side benefit.
The M1 realpath code had a significant bug - it uses the wrong offset to
truncate the
.apein the$prog.apecase.This PR also fixes a regression in
ape $prognameout of$PATHon thetwo BSDs (Free and Net) that did not implement
RealPath.