[PULL 2/4] linux-user: Implement /proc/cpuinfo for loongarch cpus

[Helge Deller <deller@kernel.org>]

From: Helge Deller <deller@gmx.de>

Mimic the entries for /proc/cpuinfo to what can be seen on the debian
porterbox loomis.debian.org.

Cc: Song Gao <gaosong@loongson.cn>
Cc: Bibo Mao <maobibo@loongson.cn>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Helge Deller <deller@gmx.de>
---
 linux-user/loongarch64/elfload.c     | 20 +++++++
 linux-user/loongarch64/target_proc.h | 79 +++++++++++++++++++++++++++-
 2 files changed, 98 insertions(+), 1 deletion(-)

diff --git a/linux-user/loongarch64/elfload.c b/linux-user/loongarch64/elfload.c
index e53957e36d..2242f20202 100644
--- a/linux-user/loongarch64/elfload.c
+++ b/linux-user/loongarch64/elfload.c
@@ -28,6 +28,26 @@ enum {
     HWCAP_LOONGARCH_LBT_MIPS = (1 << 12),
 };
 
+const char *elf_hwcap_str(uint32_t bit)
+{
+    static const char *hwcap_str[] = {
+    [__builtin_ctz(HWCAP_LOONGARCH_CPUCFG  )] = "cpucfg",
+    [__builtin_ctz(HWCAP_LOONGARCH_LAM     )] = "lam",
+    [__builtin_ctz(HWCAP_LOONGARCH_UAL     )] = "lam_bh",
+    [__builtin_ctz(HWCAP_LOONGARCH_FPU     )] = "fpu",
+    [__builtin_ctz(HWCAP_LOONGARCH_LSX     )] = "lsx",
+    [__builtin_ctz(HWCAP_LOONGARCH_LASX    )] = "lasx",
+    [__builtin_ctz(HWCAP_LOONGARCH_CRC32   )] = "crc32",
+    [__builtin_ctz(HWCAP_LOONGARCH_COMPLEX )] = "complex",
+    [__builtin_ctz(HWCAP_LOONGARCH_CRYPTO  )] = "crypto",
+    [__builtin_ctz(HWCAP_LOONGARCH_LVZ     )] = "lvz",
+    [__builtin_ctz(HWCAP_LOONGARCH_LBT_X86 )] = "lbt_x86",
+    [__builtin_ctz(HWCAP_LOONGARCH_LBT_ARM )] = "lbt_arm",
+    [__builtin_ctz(HWCAP_LOONGARCH_LBT_MIPS)] = "lbt_mips",
+    };
+
+    return bit < ARRAY_SIZE(hwcap_str) ? hwcap_str[bit] : NULL;
+}
 abi_ulong get_elf_hwcap(CPUState *cs)
 {
     LoongArchCPU *cpu = LOONGARCH_CPU(cs);
diff --git a/linux-user/loongarch64/target_proc.h b/linux-user/loongarch64/target_proc.h
index 43fe29ca72..f739520fab 100644
--- a/linux-user/loongarch64/target_proc.h
+++ b/linux-user/loongarch64/target_proc.h
@@ -1 +1,78 @@
-/* No target-specific /proc support */
+/*
+ * Loongson specific proc functions for linux-user
+ *
+ * Copyright (c) 2026 Helge Deller
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef LOONGARCH_TARGET_PROC_H
+#define LOONGARCH_TARGET_PROC_H
+
+static int open_cpuinfo(CPUArchState *cpu_env, int fd)
+{
+    uint32_t elf_hwcap = get_elf_hwcap(env_cpu(cpu_env));
+    uint32_t prid, ser_id, pabits, vabits, i, n, num_cpus;
+    bool is_64bit = is_la64(cpu_env);
+    const char *hwcap_str;
+    struct timespec res;
+    double freq_mhz;
+
+#if TARGET_LONG_BITS == 32
+    pabits = 31;
+    vabits = 31;
+#else
+    pabits = FIELD_EX32(cpu_env->cpucfg[1], CPUCFG1, PALEN);
+    vabits = FIELD_EX32(cpu_env->cpucfg[1], CPUCFG1, VALEN);
+#endif
+
+    if (clock_getres(CLOCK_REALTIME, &res) == -1) {
+        res.tv_nsec = 1;
+    }
+    freq_mhz = 1000.0 / res.tv_nsec;
+
+    ser_id = FIELD_EX32(cpu_env->cpucfg[0], CPUCFG0, SERID);
+    prid   = FIELD_EX32(cpu_env->cpucfg[0], CPUCFG0, PRID);
+
+    dprintf(fd, "system type\t\t: generic-loongson-machine\n");
+
+    num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+    for (n = 0; n < num_cpus; n++) {
+        dprintf(fd, "\nprocessor\t\t: %d\n", n);
+        dprintf(fd, "package\t\t\t: 0\n");
+        dprintf(fd, "core\t\t\t: %d\n", n);
+        dprintf(fd, "global_id\t\t: %d\n", n);
+        dprintf(fd, "CPU Family\t\t: Loongson-%dbit\n", is_64bit ? 64 : 32);
+        dprintf(fd, "Model Name\t\t: QEMU_user-v" QEMU_VERSION "\n");
+        dprintf(fd, "PRID\t\t\t: %s (%08x)\n",
+                    ser_id == PRID_SERIES_LA464 ? "LA464" :
+                    ser_id == PRID_SERIES_LA132 ? "LA132" : "Unknown",
+                    cpu_env->cpucfg[0]);
+        dprintf(fd, "CPU Revision\t\t: 0x%02x\n", prid);
+        dprintf(fd, "FPU Revision\t\t: 0x%02x\n",
+                    FIELD_EX32(cpu_env->cpucfg[2], CPUCFG2, FP_VER));
+        dprintf(fd, "CPU MHz\t\t\t: %.2f\n", freq_mhz);
+        dprintf(fd, "Address Sizes\t\t: %d bits physical, %d bits virtual\n",
+                    pabits + 1, vabits + 1);
+
+        dprintf(fd, "ISA\t\t\t:%s", " loongarch32r loongarch32s");
+        if (is_64bit) {
+            dprintf(fd, " loongarch64");
+        }
+
+        dprintf(fd, "\nFeatures\t\t:");
+        for (i = 0; i < sizeof(elf_hwcap) * 8; i++) {
+            if (!(elf_hwcap & (1 << i))) {
+                continue;
+            }
+            hwcap_str = elf_hwcap_str(i);
+            if (hwcap_str) {
+                dprintf(fd, " %s", hwcap_str);
+            }
+        }
+        dprintf(fd, "\nHardware Watchpoint\t: no\n");
+    }
+    return 0;
+}
+#define HAVE_ARCH_PROC_CPUINFO
+
+#endif /* LOONGARCH_TARGET_PROC_H */
-- 
2.54.0