riscv: use hwprobe syscall for capability detection

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24172)

1 files changed, 43 insertions, 0 deletions

diff --git a/crypto/riscvcap.c b/crypto/riscvcap.c
index db75c21b28..7683bf0fb8 100644
--- a/crypto/riscvcap.c
+++ b/crypto/riscvcap.c
@@ -17,6 +17,12 @@
 #define OPENSSL_RISCVCAP_IMPL
 #include "crypto/riscv_arch.h"
 
+#ifdef OSSL_RISCV_HWPROBE
+# include <unistd.h>
+# include <sys/syscall.h>
+# include <asm/hwprobe.h>
+#endif
+
 extern size_t riscv_vlen_asm(void);
 
 static void parse_env(const char *envstr);
@@ -71,6 +77,38 @@ static void parse_env(const char *envstr)
     }
 }
 
+#ifdef OSSL_RISCV_HWPROBE
+static long riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
+                          size_t cpu_count, unsigned long *cpus,
+                          unsigned int flags)
+{
+    return syscall(__NR_riscv_hwprobe, pairs, pair_count, cpu_count, cpus, flags);
+}
+
+static void hwprobe_to_cap()
+{
+    long ret;
+    struct riscv_hwprobe pairs[OSSL_RISCV_HWPROBE_PAIR_COUNT] = {
+        OSSL_RISCV_HWPROBE_PAIR_CONTENT
+    };
+
+    ret = riscv_hwprobe(pairs, OSSL_RISCV_HWPROBE_PAIR_COUNT, 0, NULL, 0);
+    /* if hwprobe syscall does not exist, ret would be -ENOSYS */
+    if (ret == 0) {
+        for (size_t i = 0; i < kRISCVNumCaps; ++i) {
+            for (size_t j = 0; j != OSSL_RISCV_HWPROBE_PAIR_COUNT; ++j) {
+                if (pairs[j].key == RISCV_capabilities[i].hwprobe_key
+                        && (pairs[j].value & RISCV_capabilities[i].hwprobe_value)
+                           != 0)
+                    /* Match, set relevant bit in OPENSSL_riscvcap_P[] */
+                    OPENSSL_riscvcap_P[RISCV_capabilities[i].index] |=
+                        (1 << RISCV_capabilities[i].bit_offset);
+            }
+        }
+    }
+}
+#endif /* OSSL_RISCV_HWPROBE */
+
 size_t riscv_vlen(void)
 {
     return vlen;
@@ -91,6 +129,11 @@ void OPENSSL_cpuid_setup(void)
     if ((e = getenv("OPENSSL_riscvcap"))) {
         parse_env(e);
     }
+#ifdef OSSL_RISCV_HWPROBE
+    else {
+        hwprobe_to_cap();
+    }
+#endif
 
     if (RISCV_HAS_V()) {
         vlen = riscv_vlen_asm();