Blame src/internal/tpax_tmpfile_impl.c

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/******************************************************/
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/*  tpax: a topological pax implementation            */
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/*  Copyright (C) 2020  Z. Gilboa                     */
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/*  Released under GPLv2 and GPLv3; see COPYING.TPAX. */
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/******************************************************/
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#define _GNU_SOURCE
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#include <fcntl.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <stdio.h>
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/* mkostemp might be guarded by non-standard macros */
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/* unless HAVE_NO_MKOSTEMP, assume it is available */
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extern int mkstemp(char *);
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extern int mkostemp(char *, int);
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/* __fs_tmpfile() atomically provides a private tmpfile */
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static int tpax_tmpfile_by_framework(void)
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{
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#ifdef _MIDIPIX_ABI
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	extern int __fs_tmpfile(int);
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	return __fs_tmpfile(O_CLOEXEC);
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#else
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	return (-1);
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#endif
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}
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/* O_TMPFILE atomically provides a private tmpfile */
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static int tpax_tmpfile_by_kernel(void)
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{
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#ifdef O_TMPFILE
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	return openat(AT_FDCWD,"/tmp",O_RDWR|O_TMPFILE|O_CLOEXEC,0);
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#else
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	return (-1);
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#endif
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}
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/* mk{o}stemp() provides a non-private tmpfile */
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static int tpax_mkostemp(char * tmplate)
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{
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	int fd;
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#ifdef HAVE_NO_MKOSTEMP
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	if ((fd = mkstemp(tmplate)) >= 0)
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		fcntl(fd,F_SETFD,FD_CLOEXEC);
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#else
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	fd = mkostemp(tmplate,O_CLOEXEC);
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#endif
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	return fd;
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}
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int tpax_tmpfile(void)
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{
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	int             fd;
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	unsigned        seed;
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	char            tmplate[64];
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	/* try with __fs_tmpfile() */
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	if ((fd = tpax_tmpfile_by_framework()) >= 0)
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		return fd;
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	/* try with O_TMPFILE */
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	if ((fd = tpax_tmpfile_by_kernel()) >= 0)
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		return fd;
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	/* fallback to mk{o}stemp */
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	seed = getpid();
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	memset(tmplate,0,sizeof(tmplate));
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	snprintf(tmplate,sizeof(tmplate),"/tmp/tpax_%d_%d_%d_XXXXXXXXXXXX",
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		getppid(),getpid(),rand_r(&seed));
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	return tpax_mkostemp(tmplate);
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}