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We never had an implementation for linkat() because no one used it;
now someone uses it. link() is now implemented on top of linkat().
Note the abnormal AT_SYMLINK_FOLLOW (as opposed to _NOFOLLOW) flag.
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The PSEUDO_STATBUF change (allowing operations on files over
2GB even on 32-bit systems) introduced a subtle bug; by calling
stat64() rather than real_stat(), pseudo stopped handling
chrooted paths well. In most cases, this was fine, but in the
specific case of a rename, where the stat buffers for the various
parts were actually used, it wasn't. Of particular note, pseudo
could end up creating links which had stack garbage for their
stat buffs, because it assumed that if the rename operation
succeeded, the stat operations must have succeeded.
Of course, there is no real_stat64 in the Linux port, because
there's no need for it; most code is calling __xstat64 or some
relative thereof, and even if you did really call stat64, it'd
end up routed there anyway. So we add that so that it can be
used for calls and we don't have to encode Linux-specific
magic about __xstat into the generic header.
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The _plain thing was added because of clashes between Linux
("struct stat64 for 64-bit file sizes") and Darwin ("struct stat
is already 64 bits"). But it turns out not to be enough,
because stat will *fail* if it cannot represent a file size,
so when something like unlinkat() calls a non-64-bit stat in
order to determine whether a file exists, it gets the wrong
answer if the file is over 2GB in size.
Solution: Continue using PSEUDO_STATBUF, and also provide
defines for base_stat() which can be either real_stat() or
real_stat64(), etcetera.
This eliminates any reason to need the _plain functions. It
also suggests that the other real___fxstatat() calls should
someday go away because that is an ugly, ugly, implementation
detail.
As part of testing this, fix up some bitrot which affected
Darwin (such as the continue outside of a loop, but inside
an #ifdef; that was left over from the conversion of
init_one_wrapper to a separate function).
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Spotted a couple of things during the last batch of fixes; fixing these
up so things are more consistent or clearer.
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We weren't trapping popen(), so if environment variables were in an
inconsistent state when popen() was called, Bad Things Happened. Add
a popen() wrapper. Like a couple of other special cases, is applied
even when pseudo is theoretically disabled, and that includes the antimagic
case. (But we never use popen() so that's fine.)
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ignored) rather than flags (where it was needed), meaning that the
open64 type functions didn't work as intended on 32-bit hosts.
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1. Fix *at() where dirfd is obtained through dirfd(DIR *).
The dirfd(DIR *) interface allows you to get the fd for a DIR *,
meaning you can use it with openat(), meaning you can need its
path. This causes a segfault. Also fixed the base_path
code not to segfault in that case, but first fix the
underlying problem.
2. Implement renameat()
After three long years, someone tried to use this. This was impossibly
hard back when pseudo was written, because there was only one dirfd
provided for. Thing is, now, the canonicalization happens in wrapfuncs,
so a small tweak to makewrappers to recognize that oldpath should use
olddirfd if it exists is enough to get us fully canonicalized paths
when needed.
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Previously the clone(2) wrapper unconditionallity restored the system
environment. It also invokes the checks to see if the user has requested
pseudo to be disabled or unloaded. Due to the semantics of clone, this caused
both the parent and child processes to be disabled or unloaded.
The new code adds an intermediate function, wrap_clone_child, that only
runs within the child context. This way we can be sure to only disable/unload
pseudo from within the child process. In addition, we avoid mucking with
the environment if CLONE_VM is set, since this will affect both parent and
child.
Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
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Change from internal PSEUDO_RELOADED to external PSEUDO_UNLOAD environment
variable. Enable external programs to have a safe and reliable way to unload
pseudo on the next exec*. PSEUDO_UNLOAD also will disable pseudo if we're in a
fork/clone situation in the same way PSEUDO_DISABLED=1 would.
Rename the PSEUDO_DISABLED tests, and create a similar set for the new
PSEUDO_UNLOAD.
Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
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On some Linux systems, dlsym("realpath", RTLD_NEXT) prefers
for reasons of its own to give a symbol that is also known
as old_realpath, which fails and yields EINVAL when called
with a null pointer as the second argument. This can be
avoided, on some systems, by using dlvsym() to request
the GLIBC_2.3 version of the symbol.
The wrapper logic is enhanced to allow for specifying
versions, although this currently only works for Linux
(Darwin has no dlvsym, apparently?). The test case is
a trivial program which calls realpath(name, NULL) run
with PSEUDO_DISABLED=1.
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that we add an extra fork() so we can do the setup in a child process,
but still just pass the command string to the standard system()
call.
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the 0100 bit for directories. The reason is that otherwise we create
plain files which are 0700 on disk, which means they're non-zero &0111,
which breaks euidaccess(X_OK).
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This is a spiffied-up rebase of a bunch of intermediate changes, presented
as a whole because it is, surprisingly, less confusing that way. The basic
idea is to separate the guts code into categories ranging from generic
stuff that can be the same everywhere and specific variants. The big scary
one is the Darwin support, which actually seems to run okay on 64-bit OS X
10.6. (No other variants were tested.) The other example given is support
for the old clone() syscall on RHEL 4, which affects some wrlinux use cases.
There's a few minor cleanup bits here, such as a function with inconsistent
calling conventions, but nothing really exciting.
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Peter Seebach
Mark Hatle
Seebs