uapi/auxvec: Define AT_HWCAP3 and AT_HWCAP4 aux vector, entries

The powerpc toolchain keeps a copy of the HWCAP bit masks in the TCB
for fast access by the __builtin_cpu_supports() built-in function. The
TCB space for the HWCAP entries - which are created in pairs - is an ABI
extension, so waiting to create the space for HWCAP3 and HWCAP4 until
they are needed is problematic. Define AT_HWCAP3 and AT_HWCAP4 in the
generic uapi header so they can be used in glibc to reserve space in the
powerpc TCB for their future use.

I scanned through the Linux and GLIBC source codes looking for unused
AT_* values and 29 and 30 did not seem to be used, so they are what I
went with.

Signed-off-by: Peter Bergner <bergner@linux.ibm.com>
Acked-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/a406b535-dc55-4856-8ae9-5a063644a1af@linux.ibm.com

diff --git a/include/uapi/linux/auxvec.h b/include/uapi/linux/auxvec.h
index 6991c4b8ab189d25f2cda92661f7da4a8a558a94..cc61cb9b3e9af86a41b50d5221a1b94f4d6591bb 100644 (file)
--- a/include/uapi/linux/auxvec.h
+++ b/include/uapi/linux/auxvec.h
@@ -32,6 +32,8 @@
 #define AT_HWCAP2 26   /* extension of AT_HWCAP */
 #define AT_RSEQ_FEATURE_SIZE   27      /* rseq supported feature size */
 #define AT_RSEQ_ALIGN          28      /* rseq allocation alignment */
+#define AT_HWCAP3 29   /* extension of AT_HWCAP */
+#define AT_HWCAP4 30   /* extension of AT_HWCAP */
 
 #define AT_EXECFN  31  /* filename of program */