selftests/powerpc/dexcr: Add hashst/hashchk test

Test the kernel DEXCR[NPHIE] interface and hashchk exception handling.

Introduces with it a DEXCR utils library for common DEXCR operations.

Volatile is used to prevent the compiler optimising away the signal
tests.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230616034846.311705-11-bgray@linux.ibm.com

tools/testing/selftests/powerpc/include/reg.h

@@ -19,6 +19,8 @@
 #define mb()		asm volatile("sync" : : : "memory");
 #define barrier()	asm volatile("" : : : "memory");
 
+#define SPRN_HDEXCR_RO 455	/* Userspace readonly view of SPRN_HDEXCR (471) */
+
 #define SPRN_MMCR2     769
 #define SPRN_MMCRA     770
 #define SPRN_MMCR0     779
@@ -47,6 +49,8 @@
 #define SPRN_SDAR      781
 #define SPRN_SIER      768
 
+#define SPRN_DEXCR_RO  812	/* Userspace readonly view of SPRN_DEXCR (828) */
+
 #define SPRN_TEXASR     0x82    /* Transaction Exception and Status Register */
 #define SPRN_TFIAR      0x81    /* Transaction Failure Inst Addr    */
 #define SPRN_TFHAR      0x80    /* Transaction Failure Handler Addr */

tools/testing/selftests/powerpc/include/utils.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdbool.h>
+#include <sys/signal.h>
 #include <linux/auxvec.h>
 #include <linux/perf_event.h>
 #include <asm/cputable.h>
@@ -111,6 +112,9 @@ static inline char *auxv_platform(void)
 bool is_ppc64le(void);
 int using_hash_mmu(bool *using_hash);
 
+struct sigaction push_signal_handler(int sig, void (*fn)(int, siginfo_t *, void *));
+struct sigaction pop_signal_handler(int sig, struct sigaction old_handler);
+
 /* Yes, this is evil */
 #define FAIL_IF(x)						\
 do {								\