[RFC v3] linux-user/riscv: Add syscall riscv_hwprobe

[Robbin Ehn <rehn@rivosinc.com>]

This patch adds the new syscall for the
"RISC-V Hardware Probing Interface"
(https://docs.kernel.org/riscv/hwprobe.html).

Signed-off-by: Robbin Ehn <rehn@rivosinc.com>
---
v1->v2: Moved to syscall.c
v2->v3: Separate function, get/put user
---
 linux-user/riscv/syscall32_nr.h |   1 +
 linux-user/riscv/syscall64_nr.h |   1 +
 linux-user/syscall.c            | 146 ++++++++++++++++++++++++++++++++
 3 files changed, 148 insertions(+)

diff --git a/linux-user/riscv/syscall32_nr.h b/linux-user/riscv/syscall32_nr.h
index 1327d7dffa..412e58e5b2 100644
--- a/linux-user/riscv/syscall32_nr.h
+++ b/linux-user/riscv/syscall32_nr.h
@@ -228,6 +228,7 @@
 #define TARGET_NR_accept4 242
 #define TARGET_NR_arch_specific_syscall 244
 #define TARGET_NR_riscv_flush_icache (TARGET_NR_arch_specific_syscall + 15)
+#define TARGET_NR_riscv_hwprobe (TARGET_NR_arch_specific_syscall + 14)
 #define TARGET_NR_prlimit64 261
 #define TARGET_NR_fanotify_init 262
 #define TARGET_NR_fanotify_mark 263
diff --git a/linux-user/riscv/syscall64_nr.h b/linux-user/riscv/syscall64_nr.h
index 6659751933..29e1eb2075 100644
--- a/linux-user/riscv/syscall64_nr.h
+++ b/linux-user/riscv/syscall64_nr.h
@@ -251,6 +251,7 @@
 #define TARGET_NR_recvmmsg 243
 #define TARGET_NR_arch_specific_syscall 244
 #define TARGET_NR_riscv_flush_icache (TARGET_NR_arch_specific_syscall + 15)
+#define TARGET_NR_riscv_hwprobe (TARGET_NR_arch_specific_syscall + 14)
 #define TARGET_NR_wait4 260
 #define TARGET_NR_prlimit64 261
 #define TARGET_NR_fanotify_init 262
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 83685f0aa5..e8859cd3be 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8874,6 +8874,147 @@ static int do_getdents64(abi_long dirfd, abi_long arg2, abi_long count)
 }
 #endif /* TARGET_NR_getdents64 */
 
+#if defined(TARGET_NR_riscv_hwprobe)
+
+#define RISCV_HWPROBE_KEY_MVENDORID     0
+#define RISCV_HWPROBE_KEY_MARCHID       1
+#define RISCV_HWPROBE_KEY_MIMPID        2
+
+#define RISCV_HWPROBE_KEY_BASE_BEHAVIOR 3
+#define     RISCV_HWPROBE_BASE_BEHAVIOR_IMA (1 << 0)
+
+#define RISCV_HWPROBE_KEY_IMA_EXT_0     4
+#define     RISCV_HWPROBE_IMA_FD       (1 << 0)
+#define     RISCV_HWPROBE_IMA_C        (1 << 1)
+
+#define RISCV_HWPROBE_KEY_CPUPERF_0     5
+#define     RISCV_HWPROBE_MISALIGNED_UNKNOWN     (0 << 0)
+#define     RISCV_HWPROBE_MISALIGNED_EMULATED    (1 << 0)
+#define     RISCV_HWPROBE_MISALIGNED_SLOW        (2 << 0)
+#define     RISCV_HWPROBE_MISALIGNED_FAST        (3 << 0)
+#define     RISCV_HWPROBE_MISALIGNED_UNSUPPORTED (4 << 0)
+#define     RISCV_HWPROBE_MISALIGNED_MASK        (7 << 0)
+
+struct riscv_hwprobe {
+    abi_llong  key;
+    abi_ullong value;
+};
+
+static void risc_hwprobe_fill_pairs(CPURISCVState *env,
+                                    struct riscv_hwprobe *pair,
+                                    size_t pair_count)
+{
+    const RISCVCPUConfig *cfg = riscv_cpu_cfg(env);
+
+    for (; pair_count > 0; pair_count--, pair++) {
+        abi_llong key;
+        abi_ullong value;
+        __put_user(0, &pair->value);
+        __get_user(key, &pair->key);
+        switch (key) {
+        case RISCV_HWPROBE_KEY_MVENDORID:
+            __put_user(cfg->mvendorid, &pair->value);
+            break;
+        case RISCV_HWPROBE_KEY_MARCHID:
+            __put_user(cfg->marchid, &pair->value);
+            break;
+        case RISCV_HWPROBE_KEY_MIMPID:
+            __put_user(cfg->mimpid, &pair->value);
+            break;
+        case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
+            value = riscv_has_ext(env, RVI) &&
+                    riscv_has_ext(env, RVM) &&
+                    riscv_has_ext(env, RVA) ?
+                    RISCV_HWPROBE_BASE_BEHAVIOR_IMA : 0;
+            __put_user(value, &pair->value);
+            break;
+        case RISCV_HWPROBE_KEY_IMA_EXT_0:
+            value = riscv_has_ext(env, RVF) &&
+                    riscv_has_ext(env, RVD) ?
+                    RISCV_HWPROBE_IMA_FD : 0;
+            value |= riscv_has_ext(env, RVC) ?
+                     RISCV_HWPROBE_IMA_C : pair->value;
+            __put_user(value, &pair->value);
+            break;
+        case RISCV_HWPROBE_KEY_CPUPERF_0:
+            __put_user(RISCV_HWPROBE_MISALIGNED_FAST, &pair->value);
+            break;
+        default:
+            __put_user(-1, &pair->key);
+            break;
+        }
+    }
+}
+
+static int cpu_set_valid(abi_long arg3, abi_long arg4)
+{
+    int ret, i, tmp;
+    size_t host_mask_size, target_mask_size;
+    unsigned long *host_mask;
+
+    /*
+     * cpu_set_t represent CPU masks as bit masks of type unsigned long *.
+     * arg3 contains the cpu count.
+     */
+    tmp = (8 * sizeof(abi_ulong));
+    target_mask_size = ((arg3 + tmp - 1) / tmp) * sizeof(abi_ulong);
+    host_mask_size = (target_mask_size + (sizeof(*host_mask) - 1)) &
+                     ~(sizeof(*host_mask) - 1);
+
+    host_mask = alloca(host_mask_size);
+
+    ret = target_to_host_cpu_mask(host_mask, host_mask_size,
+                                  arg4, target_mask_size);
+    if (ret != 0) {
+        return ret;
+    }
+
+    for (i = 0 ; i < host_mask_size / sizeof(*host_mask); i++) {
+        if (host_mask[i] != 0) {
+            return 0;
+        }
+    }
+    return -TARGET_EINVAL;
+}
+
+static abi_long do_riscv_hwprobe(CPUArchState *cpu_env, abi_long arg1,
+                                 abi_long arg2, abi_long arg3,
+                                 abi_long arg4, abi_long arg5)
+{
+    int ret;
+    struct riscv_hwprobe *host_pairs;
+
+    /* flags must be 0 */
+    if (arg5 != 0) {
+        return -TARGET_EINVAL;
+    }
+
+    /* check cpu_set */
+    if (arg3 != 0) {
+        ret = cpu_set_valid(arg3, arg4);
+        if (ret != 0) {
+            return ret;
+        }
+    } else if (arg4 != 0) {
+        return -TARGET_EINVAL;
+    }
+
+    /* no pairs */
+    if (arg2 == 0) {
+        return 0;
+    }
+
+    host_pairs = lock_user(VERIFY_WRITE, arg1,
+                           sizeof(*host_pairs) * (size_t)arg2, 0);
+    if (host_pairs == NULL) {
+        return -TARGET_EFAULT;
+    }
+    risc_hwprobe_fill_pairs(cpu_env, host_pairs, arg2);
+    unlock_user(host_pairs, arg1, sizeof(*host_pairs) * (size_t)arg2);
+    return 0;
+}
+#endif /* TARGET_NR_riscv_hwprobe */
+
 #if defined(TARGET_NR_pivot_root) && defined(__NR_pivot_root)
 _syscall2(int, pivot_root, const char *, new_root, const char *, put_old)
 #endif
@@ -13571,6 +13712,11 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
         return ret;
 #endif
 
+#if defined(TARGET_NR_riscv_hwprobe)
+    case TARGET_NR_riscv_hwprobe:
+        return do_riscv_hwprobe(cpu_env, arg1, arg2, arg3, arg4, arg5);
+#endif
+
     default:
         qemu_log_mask(LOG_UNIMP, "Unsupported syscall: %d\n", num);
         return -TARGET_ENOSYS;
-- 
2.39.2