linux: add definitions for hugetlb page size encodings

A desired hugetlb page size can be encoded in the flags parameter of
system calls such as mmap() and shmget(). The Linux UAPI headers have
included explicit definitions for these encodings since v4.14.

This patch adds these definitions that are used along with MAP_HUGETLB
and SHM_HUGETLB flags as specified in the corresponding man pages. This
relieves programs from having to duplicate and/or compute the encodings
manually.

Additionally, the filter on these definitions in tst-mman-consts.py is
removed, as suggested by Florian. I then ran this tests successfully,
confirming the alignment with the kernel headers.

  PASS: misc/tst-mman-consts
  original exit status 0

Signed-off-by: Carlos Llamas <cmllamas@google.com>
Tested-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/bits/shm.h b/sysdeps/unix/sysv/linux/bits/shm.h
index 95f7863913..76144f5ad4 100644
--- a/sysdeps/unix/sysv/linux/bits/shm.h
+++ b/sysdeps/unix/sysv/linux/bits/shm.h
@@ -58,6 +58,28 @@ typedef __syscall_ulong_t shmatt_t;
 # define SHM_HUGETLB	04000	/* segment is mapped via hugetlb */
 # define SHM_NORESERVE	010000	/* don't check for reservations */
 
+/* When SHM_HUGETLB is set, bits [26:31] encode the log2 of the huge page size.
+   The following definitions are associated with this huge page size encoding.
+   It is responsibility of the application to know which sizes are supported on
+   the running system.  See shmget(2) man page for details.  */
+
+#define SHM_HUGE_SHIFT	26
+#define SHM_HUGE_MASK	0x3f
+
+#define SHM_HUGE_16KB	(14 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_64KB	(16 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_512KB	(19 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_1MB	(20 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_2MB	(21 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_8MB	(23 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_16MB	(24 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_32MB	(25 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_256MB	(28 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_512MB	(29 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_1GB	(30 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_2GB	(31 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_16GB	(34U << SHM_HUGE_SHIFT)
+
 struct	shminfo
   {
     __syscall_ulong_t shmmax;