linux-user: Add ELF_PLATFORM for arm

The 32-bit kernel has strings for v4, v5, v6, v7, v7m.
The 64-bit kernel, in compat mode, has strings for v8.

Fixes: https://bugs.launchpad.net/bugs/1813034
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20190212074840.13542-2-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/elfload.c

@@ -500,6 +500,37 @@ static uint32_t get_elf_hwcap2(void)
 #undef GET_FEATURE
 #undef GET_FEATURE_ID
 
+#define ELF_PLATFORM get_elf_platform()
+
+static const char *get_elf_platform(void)
+{
+    CPUARMState *env = thread_cpu->env_ptr;
+
+#ifdef TARGET_WORDS_BIGENDIAN
+# define END  "b"
+#else
+# define END  "l"
+#endif
+
+    if (arm_feature(env, ARM_FEATURE_V8)) {
+        return "v8" END;
+    } else if (arm_feature(env, ARM_FEATURE_V7)) {
+        if (arm_feature(env, ARM_FEATURE_M)) {
+            return "v7m" END;
+        } else {
+            return "v7" END;
+        }
+    } else if (arm_feature(env, ARM_FEATURE_V6)) {
+        return "v6" END;
+    } else if (arm_feature(env, ARM_FEATURE_V5)) {
+        return "v5" END;
+    } else {
+        return "v4" END;
+    }
+
+#undef END
+}
+
 #else
 /* 64 bit ARM definitions */
 #define ELF_START_MMAP 0x80000000