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Blame src/helper/slbt_realpath.c

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/*******************************************************************/
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/*  slibtool: a skinny libtool implementation, written in C        */
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/*  Copyright (C) 2016--2020  Z. Gilboa                            */
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/*  Released under the Standard MIT License; see COPYING.SLIBTOOL. */
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/*******************************************************************/
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#include <fcntl.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <slibtool/slibtool.h>
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#include "slibtool_driver_impl.h"
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#include "slibtool_readlink_impl.h"
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#ifdef __unix__
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#include <sys/syscall.h>
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#endif
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#ifdef _MIDIPIX_ABI
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#include <sys/fs.h>
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#endif
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#ifndef ENOTSUP
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#define ENOTSUP EOPNOTSUPP
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#endif
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#ifdef SYS___realpathat
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extern long syscall(int, ...);
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#endif
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int slbt_realpath(
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	int             fdat,
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	const char *    path,
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	int             options,
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	char *          buf,
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	size_t          buflen)
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{
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	int             ret;
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	int             fd;
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	int             fdproc;
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	struct stat     st;
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	struct stat     stproc;
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	char    procfspath[36];
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	/* common validation */
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	if (!buf || (options & O_CREAT)) {
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		errno = EINVAL;
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		return -1;
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	}
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	/* framework-based wrapper */
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#ifdef _MIDIPIX_ABI
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	return __fs_rpath(fdat,path,options,buf,buflen);
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#endif
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#ifdef SYS___realpathat
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	return syscall(SYS___realpathat,fdat,path,buf,buflen,0);
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#endif
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	/* buflen */
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	if (buflen < PATH_MAX) {
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		errno = ENOBUFS;
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		return -1;
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	}
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	/* AT_FDCWD */
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	if (fdat == AT_FDCWD) {
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		return realpath(path,buf) ? 0 : -1;
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	}
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	/* /proc/self/fd */
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	if ((fd = openat(fdat,path,options,0)) < 0)
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		return -1;
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	sprintf(procfspath,"/proc/self/fd/%d",fd);
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	if (slbt_readlinkat(fdat,procfspath,buf,buflen)) {
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		close(fd);
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		return -1;
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	}
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	if ((fdproc = openat(AT_FDCWD,buf,options|O_NOFOLLOW,0)) < 0) {
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		close(fd);
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		errno = ELOOP;
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		return -1;
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	}
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	ret = fstat(fd,&st) || fstat(fdproc,&stproc);
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	close(fd);
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	close(fdproc);
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	if (ret || (st.st_dev != stproc.st_dev) || (st.st_ino != stproc.st_ino)) {
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		errno = ENOTSUP;
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		return -1;
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	}
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	return 0;
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}