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

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.

(cherry picked from commit a008c76b56e4f958cf5a0d6f67d29fade89421b7)

ChangeLog

@@ -1,3 +1,14 @@
+2019-07-15  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.
+
 2019-07-12  Szabolcs Nagy  <szabolcs.nagy@arm.com>
 
 	* sysdeps/aarch64/dl-machine.h (elf_machine_lazy_rel): Check

posix/tst-mmap-offset.c

@@ -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;
 }

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;
+}

sysdeps/unix/sysv/linux/mips/mmap_info.h

@@ -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
+}

sysdeps/unix/sysv/linux/mmap64.c

@@ -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)