| Age | Commit message (Collapse) | Author | Lines |
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| 2020年11月30日 | implement realpath directly instead of using procfs readlink | Rich Felker | -23/+136 |
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inability to use realpath in chroot/container without procfs access
and at early boot prior to mount of /proc has been an ongoing issue,
and it turns out realpath was one of the last remaining interfaces
that needed procfs for its core functionality. during investigation
while reimplementing, it was determined that there were also serious
problems with the procfs-based implementation. most seriously it was
unsafe on pre-O_PATH kernels, and unlike other places where O_PATH was
used, the unsafety was hard or impossible to fix because O_NOFOLLOW
can't be used (since the whole purpose was to follow symlinks).
the new implementation is a direct one, performing readlink on each
path component to resolve it. an explicit stack, as opposed to
recursion, is used to represent the remaining components to be
processed. the stack starts out holding just the input string, and
reading a link pushes the link contents onto the stack.
unlike many other implementations, this one does not call getcwd
initially for relative pathnames. instead it accumulates initial ..
components to be applied to the working directory if the result is
still a relative path. this avoids calling getcwd (which may fail) at
all when symlink traversal will eventually yield an absolute path. it
also doesn't use any form of stat operation; instead it arranges for
readlink to tell it when a non-directory is used in a context where a
directory is needed. this minimizes the number of syscalls needed,
avoids accessing inodes when the directory table suffices, and reduces
the amount of code pulled in for static linking.
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| 2018年09月12日 | move and deduplicate declarations of __procfdname to make it checkable | Rich Felker | -2/+0 |
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syscall.h was chosen as the header to declare it, since its intended
usage is alongside syscalls as a fallback for operations the direct
syscall does not support.
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| 2014年05月24日 | support kernels with no SYS_open syscall, only SYS_openat | Rich Felker | -1/+1 |
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open is handled specially because it is used from so many places, in
so many variants (2 or 3 arguments, setting errno or not, and
cancellable or not). trying to do it as a function would not only
increase bloat, but would also risk subtle breakage.
this is the first step towards supporting "new" archs where linux
lacks "old" syscalls.
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| 2013年08月31日 | remove incorrect cancellation points from realpath | Rich Felker | -4/+4 |
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| 2013年08月31日 | debloat realpath's allocation strategy | Rich Felker | -12/+6 |
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rather than allocating a PATH_MAX-sized buffer when the caller does
not provide an output buffer, work first with a PATH_MAX-sized temp
buffer with automatic storage, and either copy it to the caller's
buffer or strdup it on success. this not only avoids massive memory
waste, but also avoids pulling in free (and thus the full malloc
implementation) unnecessarily in static programs.
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| 2013年08月31日 | make realpath use O_PATH when opening the file | Rich Felker | -1/+1 |
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this avoids failure if the file is not readable and avoids odd
behavior for device nodes, etc. on old kernels that lack O_PATH, the
old behavior (O_RDONLY) will naturally happen as the fallback.
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| 2013年08月02日 | debloat code that depends on /proc/self/fd/%d with shared function | Rich Felker | -1/+3 |
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I intend to add more Linux workarounds that depend on using these
pathnames, and some of them will be in "syscall" functions that, from
an anti-bloat standpoint, should not depend on the whole snprintf
framework.
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| 2012年09月29日 | fix some more O_CLOEXEC/SOCK_CLOEXEC issues | Rich Felker | -1/+1 |
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| 2012年09月06日 | use restrict everywhere it's required by c99 and/or posix 2008 | Rich Felker | -1/+1 |
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to deal with the fact that the public headers may be used with pre-c99
compilers, __restrict is used in place of restrict, and defined
appropriately for any supported compiler. we also avoid the form
[restrict] since older versions of gcc rejected it due to a bug in the
original c99 standard, and instead use the form *restrict.
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| 2011年06月18日 | fix memory leak on failure in realpath | Rich Felker | -4/+4 |
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| 2011年04月17日 | minimal realpath implementation using /proc | Rich Felker | -0/+43 |
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clean and simple, but fails when the caller does not have permissions
to open the file for reading or when /proc is not available. i may
replace this with a full implementation later, possibly leaving this
version as an optimization to use when it works.
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| 2011年02月12日 | initial check-in, version 0.5.0 v0.5.0 | Rich Felker | -0/+6 |
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