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

The fix for BZ#21270 (commit 158d5fa0e19) 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.

1 files changed, 16 insertions, 0 deletions

diff --git a/sysdeps/generic/mmap_info.h b/sysdeps/generic/mmap_info.h
new file mode 100644
index 0000000000..b3087df2d3
--- /dev/null
+++ b/sysdeps/generic/mmap_info.h
@@ -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;
+}