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posix: Fix large mmap64 offset for mips64n32 (BZ#24699)

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The fix for BZ#21270 (commit 158d5fa0e1) added a mask to avoid offset larger
than 1^44 to be used along __NR_mmap2.  However mips64n32 users __NR_mmap,
as mips64n64, but still defines off_t as old non-LFS type (other ILP32, such
x32, defines off_t being equal to off64_t).  This leads to use the same
mask meant only for __NR_mmap2 call for __NR_mmap, thus limiting the maximum
offset it can use with mmap64.

This patch fixes by setting the high mask only for __NR_mmap2 usage. The
posix/tst-mmap-offset.c already tests it and also fails for mips64n32. The
patch also change the test to check for an arch-specific header that defines
the maximum supported offset.

Checked on x86_64-linux-gnu, i686-linux-gnu, and I also tests tst-mmap-offset
on qemu simulated mips64 with kernel 3.2.0 kernel for both mips-linux-gnu and
mips64-n32-linux-gnu.

	[BZ #24699]
	* posix/tst-mmap-offset.c: Mention BZ #24699.
	(do_test_bz21270): Rename to do_test_large_offset and use
	mmap64_maximum_offset to check for maximum expected offset value.
	* sysdeps/generic/mmap_info.h: New file.
	* sysdeps/unix/sysv/linux/mips/mmap_info.h: Likewise.
	* sysdeps/unix/sysv/linux/mmap64.c (MMAP_OFF_HIGH_MASK): Define iff
	__NR_mmap2 is used.
This commit is contained in:
Adhemerval Zanella 2019-06-18 14:09:09 -03:00
parent 99135114ba
commit a008c76b56
5 changed files with 53 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
ChangeLog
View File

@ -1,3 +1,14 @@
2019-07-10 Adhemerval Zanella <adhemerval.zanella@linaro.org>
[BZ #24699]
* posix/tst-mmap-offset.c: Mention BZ #24699.
(do_test_bz21270): Rename to do_test_large_offset and use
mmap64_maximum_offset to check for maximum expected offset value.
* sysdeps/generic/mmap_info.h: New file.
* sysdeps/unix/sysv/linux/mips/mmap_info.h: Likewise.
* sysdeps/unix/sysv/linux/mmap64.c (MMAP_OFF_HIGH_MASK): Define iff
__NR_mmap2 is used.
2019-07-10 DJ Delorie <dj@redhat.com>
Sergei Trofimovich <slyfox@inbox.ru>

9
posix/tst-mmap-offset.c
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@ -1,4 +1,4 @@
/* BZ #18877 and #21270 mmap offset test.
/* BZ #18877, BZ #21270, and BZ #24699 mmap offset test.
Copyright (C) 2015-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@ -24,6 +24,7 @@
#include <unistd.h>
#include <errno.h>
#include <sys/mman.h>
#include <mmap_info.h>
#include <support/check.h>
@ -76,7 +77,7 @@ do_test_bz18877 (void)
/* Check if invalid offset are handled correctly by mmap. */
static int
do_test_bz21270 (void)
do_test_large_offset (void)
{
/* For architectures with sizeof (off_t) < sizeof (off64_t) mmap is
implemented with __SYS_mmap2 syscall and the offset is represented in
@ -90,7 +91,7 @@ do_test_bz21270 (void)
const size_t length = 4096;
void *addr = mmap64 (NULL, length, prot, flags, fd, offset);
if (sizeof (off_t) < sizeof (off64_t))
if (mmap64_maximum_offset (page_shift) < UINT64_MAX)
{
if ((addr != MAP_FAILED) && (errno != EINVAL))
FAIL_RET ("mmap succeed");
@ -110,7 +111,7 @@ do_test (void)
int ret = 0;
ret += do_test_bz18877 ();
ret += do_test_bz21270 ();
ret += do_test_large_offset ();
return ret;
}

16
sysdeps/generic/mmap_info.h Normal file
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@ -0,0 +1,16 @@
/* As default architectures with sizeof (off_t) < sizeof (off64_t) the mmap is
implemented with __SYS_mmap2 syscall and the offset is represented in
multiples of page size. For offset larger than
'1 << (page_shift + 8 * sizeof (off_t))' (that is, 1<<44 on system with
page size of 4096 bytes) the system call silently truncates the offset.
For this case, glibc mmap implementation returns EINVAL. */
/* Return the maximum value expected as offset argument in mmap64 call. */
static inline uint64_t
mmap64_maximum_offset (long int page_shift)
{
if (sizeof (off_t) < sizeof (off64_t))
return (UINT64_C(1) << (page_shift + (8 * sizeof (off_t)))) - 1;
else
return UINT64_MAX;
}

13
sysdeps/unix/sysv/linux/mips/mmap_info.h Normal file
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@ -0,0 +1,13 @@
/* mips64n32 uses __NR_mmap for mmap64 while still having sizeof (off_t)
smaller than sizeof (off64_t). So it allows mapping large offsets
using mmap64 than 32-bit archs which uses __NR_mmap2. */
static inline uint64_t
mmap64_maximum_offset (long int page_shift)
{
#if _MIPS_SIM == _ABIN32 || _MIPS_SIM == _ABI64
return UINT64_MAX;
#else
return (UINT64_C(1) << (page_shift + (8 * sizeof (off_t)))) - 1;
#endif
}

9
sysdeps/unix/sysv/linux/mmap64.c
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@ -23,11 +23,18 @@
#include <sysdep.h>
#include <mmap_internal.h>
#ifdef __NR_mmap2
/* To avoid silent truncation of offset when using mmap2, do not accept
offset larger than 1 << (page_shift + off_t bits). For archictures with
32 bits off_t and page size of 4096 it would be 1^44. */
#define MMAP_OFF_HIGH_MASK \
# define MMAP_OFF_HIGH_MASK \
((-(MMAP2_PAGE_UNIT << 1) << (8 * sizeof (off_t) - 1)))
#else
/* Some ABIs might use __NR_mmap while having sizeof (off_t) smaller than
sizeof (off64_t) (currently only MIPS64n32). For this case just set
zero the higher bits so mmap with large offset does not fail. */
# define MMAP_OFF_HIGH_MASK 0x0
#endif
#define MMAP_OFF_MASK (MMAP_OFF_HIGH_MASK | MMAP_OFF_LOW_MASK)