[PATCH qemu v3] linux-user: Emulate /proc/cpuinfo output for riscv

[Afonso Bordado <afonsobordado@gmail.com>]

RISC-V does not expose all extensions via hwcaps, thus some userspace
applications may want to query these via /proc/cpuinfo.

Currently when querying this file the host's file is shown instead
which is slightly confusing. Emulate a basic /proc/cpuinfo file
with mmu info and an ISA string.

Signed-off-by: Afonso Bordado <afonsobordado@gmail.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
---

Thanks everyone for reviewing! Should I resend this once the 8.0
freeze is over? Or does someone queue it for inclusion in the next
version?


Changes from V2:
- Update ChangeLog Location

Changes from V1:
- Call `g_free` on ISA string.
- Use `riscv_cpu_cfg` API.
- Query `cpu_env->xl` to check for RV32.


  linux-user/syscall.c              | 34 +++++++++++++++++++++++++++++--
  tests/tcg/riscv64/Makefile.target |  1 +
  tests/tcg/riscv64/cpuinfo.c       | 30 +++++++++++++++++++++++++++
  3 files changed, 63 insertions(+), 2 deletions(-)
  create mode 100644 tests/tcg/riscv64/cpuinfo.c

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 24cea6fb6a..0388f8b0b0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8230,7 +8230,8 @@ void target_exception_dump(CPUArchState *env, const char *fmt, int code)
  }
  
  #if HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN || \
-    defined(TARGET_SPARC) || defined(TARGET_M68K) || defined(TARGET_HPPA)
+    defined(TARGET_SPARC) || defined(TARGET_M68K) || defined(TARGET_HPPA) || \
+    defined(TARGET_RISCV)
  static int is_proc(const char *filename, const char *entry)
  {
      return strcmp(filename, entry) == 0;
@@ -8308,6 +8309,35 @@ static int open_cpuinfo(CPUArchState *cpu_env, int fd)
  }
  #endif
  
+#if defined(TARGET_RISCV)
+static int open_cpuinfo(CPUArchState *cpu_env, int fd)
+{
+    int i;
+    int num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+    RISCVCPU *cpu = env_archcpu(cpu_env);
+    const RISCVCPUConfig *cfg = riscv_cpu_cfg((CPURISCVState *) cpu_env);
+    char *isa_string = riscv_isa_string(cpu);
+    const char *mmu;
+
+    if (cfg->mmu) {
+        mmu = (cpu_env->xl == MXL_RV32) ? "sv32"  : "sv48";
+    } else {
+        mmu = "none";
+    }
+
+    for (i = 0; i < num_cpus; i++) {
+        dprintf(fd, "processor\t: %d\n", i);
+        dprintf(fd, "hart\t\t: %d\n", i);
+        dprintf(fd, "isa\t\t: %s\n", isa_string);
+        dprintf(fd, "mmu\t\t: %s\n", mmu);
+        dprintf(fd, "uarch\t\t: qemu\n\n");
+    }
+
+    g_free(isa_string);
+    return 0;
+}
+#endif
+
  #if defined(TARGET_M68K)
  static int open_hardware(CPUArchState *cpu_env, int fd)
  {
@@ -8332,7 +8362,7 @@ static int do_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, int
  #if HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN
          { "/proc/net/route", open_net_route, is_proc },
  #endif
-#if defined(TARGET_SPARC) || defined(TARGET_HPPA)
+#if defined(TARGET_SPARC) || defined(TARGET_HPPA) || defined(TARGET_RISCV)
          { "/proc/cpuinfo", open_cpuinfo, is_proc },
  #endif
  #if defined(TARGET_M68K)
diff --git a/tests/tcg/riscv64/Makefile.target
b/tests/tcg/riscv64/Makefile.target
index cc3ed65ffd..df93a2ce1f 100644
--- a/tests/tcg/riscv64/Makefile.target
+++ b/tests/tcg/riscv64/Makefile.target
@@ -4,6 +4,7 @@
  VPATH += $(SRC_PATH)/tests/tcg/riscv64
  TESTS += test-div
  TESTS += noexec
+TESTS += cpuinfo
  
  # Disable compressed instructions for test-noc
  TESTS += test-noc
diff --git a/tests/tcg/riscv64/cpuinfo.c b/tests/tcg/riscv64/cpuinfo.c
new file mode 100644
index 0000000000..296abd0a8c
--- /dev/null
+++ b/tests/tcg/riscv64/cpuinfo.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#define BUFFER_SIZE 1024
+
+int main(void)
+{
+    char buffer[BUFFER_SIZE];
+    FILE *fp = fopen("/proc/cpuinfo", "r");
+    assert(fp != NULL);
+
+    while (fgets(buffer, BUFFER_SIZE, fp) != NULL) {
+        if (strstr(buffer, "processor") != NULL) {
+            assert(strstr(buffer, "processor\t: ") == buffer);
+        } else if (strstr(buffer, "hart") != NULL) {
+            assert(strstr(buffer, "hart\t\t: ") == buffer);
+        } else if (strstr(buffer, "isa") != NULL) {
+            assert(strcmp(buffer, "isa\t\t: rv64imafdc_zicsr_zifencei\n") == 0);
+        } else if (strstr(buffer, "mmu") != NULL) {
+            assert(strcmp(buffer, "mmu\t\t: sv48\n") == 0);
+        } else if (strstr(buffer, "uarch") != NULL) {
+            assert(strcmp(buffer, "uarch\t\t: qemu\n") == 0);
+        }
+    }
+
+    fclose(fp);
+    return 0;
+}
-- 
2.34.7