[Qemu-devel] [PATCH v4 03/11] linux-user: Add support for sysfs() syscall

[Aleksandar Markovic]

From: Aleksandar Markovic <address@hidden>

This patch implements Qemu user mode sysfs() syscall support.

Syscall sysfs() involves returning information about the filesystem types
currently present in the kernel, and can operate in three distinct flavors,
depending on its first argument.

The implementation is based on invocation of host's sysfs(), and
its key part is in the correspondent case segment of the main switch
statement of the function do_syscall(), in file linux-user/syscalls.c.
All necessary conversions of data structures from target to host and from
host to target are covered. Based on the value of the first argument, three
cases are distinguished, and such conversions are implemented separately
for each case. Relevant support for "-strace" option is included in files
linux-user/strace.c and linux-user/strace.list.

This patch also fixes failures of LTP tests sysfs01, sysfs02, sysfs03,
sysfs04, sysfs05, and sysfs06, if executed in Qemu user mode.

Signed-off-by: Aleksandar Markovic <address@hidden>
---
 linux-user/strace.c    | 25 +++++++++++++++++++++++++
 linux-user/strace.list |  2 +-
 linux-user/syscall.c   | 42 +++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index 4524c70..61911e7 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -2151,6 +2151,31 @@ print_kill(const struct syscallname *name,
 }
 #endif
 
+#if defined(TARGET_NR_sysfs)
+static void
+print_sysfs(const struct syscallname *name,
+    abi_long arg0, abi_long arg1, abi_long arg2,
+    abi_long arg3, abi_long arg4, abi_long arg5)
+{
+    print_syscall_prologue(name);
+    switch (arg0) {
+    case 1:
+        print_raw_param("%d", arg0, 1);
+        print_string(arg1, 1);
+        break;
+    case 2:
+        print_raw_param("%d", arg0, 0);
+        print_raw_param("%u", arg1, 0);
+        print_pointer(arg2, 1);
+        break;
+    default:
+        print_raw_param("%d", arg0, 1);
+        break;
+    }
+    print_syscall_epilogue(name);
+}
+#endif
+
 /*
  * An array of all of the syscalls we know about
  */
diff --git a/linux-user/strace.list b/linux-user/strace.list
index 00b2e9b..0bf1bea 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -1371,7 +1371,7 @@
 { TARGET_NR_sys_epoll_wait, "sys_epoll_wait" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_sysfs
-{ TARGET_NR_sysfs, "sysfs" , NULL, NULL, NULL },
+{ TARGET_NR_sysfs, "sysfs" , NULL, print_sysfs, NULL },
 #endif
 #ifdef TARGET_NR_sysinfo
 { TARGET_NR_sysinfo, "sysinfo" , NULL, NULL, NULL },
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index eab9207..3436ee6 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9549,7 +9549,47 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
 #endif
 #ifdef TARGET_NR_sysfs
     case TARGET_NR_sysfs:
-        goto unimplemented;
+        switch (arg1) {
+        case 1:
+            {
+                if (arg2 != 0) {
+                    p = lock_user_string(arg2);
+                    if (!p) {
+                        goto efault;
+                    }
+                    ret = get_errno(syscall(__NR_sysfs, arg1, p));
+                    unlock_user(p, arg2, 0);
+                } else {
+                    ret = get_errno(syscall(__NR_sysfs, arg1, NULL));
+                }
+            }
+            break;
+        case 2:
+            {
+                if (arg3 != 0) {
+                    char buf[PATH_MAX];
+                    int len;
+                    memset(buf, 0, PATH_MAX);
+                    ret = get_errno(syscall(__NR_sysfs, arg1, arg2, buf));
+                    len = PATH_MAX;
+                    if (len > strlen(buf)) {
+                        len = strlen(buf);
+                    }
+                    if (copy_to_user(arg3, buf, len) != 0) {
+                        goto efault;
+                    }
+                } else {
+                    ret = get_errno(syscall(__NR_sysfs, arg1, arg2, NULL));
+                }
+            }
+            break;
+        case 3:
+            ret = get_errno(syscall(__NR_sysfs, arg1));
+            break;
+        default:
+            ret = -EINVAL;
+        }
+        break;
 #endif
     case TARGET_NR_personality:
         ret = get_errno(personality(arg1));
-- 
2.9.3