From: Filip Bozuta <Filip.Bozuta@syrmia.com>

This patch implements strace argument printing functionality for following syscalls:

    *getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value

        ssize_t getxattr(const char *path, const char *name, void *value, size_t size)
        ssize_t lgetxattr(const char *path, const char *name, void *value, size_t size)
        ssize_t fgetxattr(int fd, const char *name, void *value, size_t size)
        man page: https://www.man7.org/linux/man-pages/man2/getxattr.2.html

    *listxattr, llistxattr, flistxattr - list extended attribute names

        ssize_t listxattr(const char *path, char *list, size_t size)
        ssize_t llistxattr(const char *path, char *list, size_t size)
        ssize_t flistxattr(int fd, char *list, size_t size)
        man page: https://www.man7.org/linux/man-pages/man2/listxattr.2.html

    *removexattr, lremovexattr, fremovexattr - remove an extended attribute

         int removexattr(const char *path, const char *name)
         int lremovexattr(const char *path, const char *name)
         int fremovexattr(int fd, const char *name)
         man page: https://www.man7.org/linux/man-pages/man2/removexattr.2.html

Implementation notes:

    All of the syscalls have strings as argument types and thus a separate
    printing function was stated in file "strace.list" for every one of them.
    All of these printing functions were defined in "strace.c" using existing
    printing functions for appropriate argument types:
       "print_string()" - for (const char*) type
       "print_pointer()" - for (char*) and (void *) type
       "print_raw_param()" for (int) and (size_t) type
    Syscalls "getxattr()" and "lgetxattr()" have the same number and type of
    arguments and thus their print functions ("print_getxattr", "print_lgetxattr")
    share a same definition. The same statement applies to syscalls "listxattr()"
    and "llistxattr()".
    Function "print_syscall_ret_listxattr()" was added to print the returned list
    of extended attributes for syscalls "print_listxattr(), print_llistxattr() and
    print_flistxattr()".

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
---
 linux-user/strace.c    | 95 ++++++++++++++++++++++++++++++++++++++++++
 linux-user/strace.list | 15 ++++---
 2 files changed, 104 insertions(+), 6 deletions(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index 4f85606c19..a7c3ea8df3 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -834,6 +834,41 @@ print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret,
 }
 #endif
 
+#if defined(TARGET_NR_listxattr) || defined(TARGET_NR_llistxattr) \
+ || defined(TARGGET_NR_flistxattr)
+static void
+print_syscall_ret_listxattr(const struct syscallname *name, abi_long ret,
+                            abi_long arg0, abi_long arg1, abi_long arg2,
+                            abi_long arg3, abi_long arg4, abi_long arg5)
+{
+    const char *errstr = NULL;
+
+    SYSCALL_RET_ERR(ret, errstr);
+
+    if (ret >= 0) {
+        qemu_log(TARGET_ABI_FMT_ld, ret);
+        qemu_log(" (list = ");
+        if (arg1 != 0) {
+            abi_long attr = arg1;
+            while (target_strlen(attr) != 0) {
+                if (attr != arg1) {
+                    qemu_log(",");
+                }
+                print_string(attr, 1);
+                attr += target_strlen(attr) + 1;
+            }
+        } else {
+            qemu_log("NULL");
+        }
+        qemu_log(")");
+    }
+
+    qemu_log("\n");
+}
+#define print_syscall_ret_llistxattr     print_syscall_ret_listxattr
+#define print_syscall_ret_flistxattr     print_syscall_ret_listxattr
+#endif
+
 UNUSED static struct flags access_flags[] = {
     FLAG_GENERIC(F_OK),
     FLAG_GENERIC(R_OK),
@@ -1641,6 +1676,66 @@ print_fcntl(const struct syscallname *name,
 #define print_fcntl64   print_fcntl
 #endif
 
+#ifdef TARGET_NR_fgetxattr
+static void
+print_fgetxattr(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);
+    print_raw_param("%d", arg0, 0);
+    print_string(arg1, 0);
+    print_pointer(arg2, 0);
+    print_raw_param(TARGET_FMT_lu, arg3, 1);
+    print_syscall_epilogue(name);
+}
+#endif
+
+#ifdef TARGET_NR_flistxattr
+static void
+print_flistxattr(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);
+    print_raw_param("%d", arg0, 0);
+    print_pointer(arg1, 0);
+    print_raw_param(TARGET_FMT_lu, arg2, 1);
+    print_syscall_epilogue(name);
+}
+#endif
+
+#if defined(TARGET_NR_getxattr) || defined(TARGET_NR_lgetxattr)
+static void
+print_getxattr(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);
+    print_string(arg0, 0);
+    print_string(arg1, 0);
+    print_pointer(arg2, 0);
+    print_raw_param(TARGET_FMT_lu, arg3, 1);
+    print_syscall_epilogue(name);
+}
+#define print_lgetxattr     print_getxattr
+#endif
+
+#if defined(TARGET_NR_listxattr) || defined(TARGET_NR_llistxattr)
+static void
+print_listxattr(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);
+    print_string(arg0, 0);
+    print_pointer(arg1, 0);
+    print_raw_param(TARGET_FMT_lu, arg2, 1);
+    print_syscall_epilogue(name);
+}
+#define print_llistxattr     print_listxattr
+#endif
+
 #ifdef TARGET_NR_futimesat
 static void
 print_futimesat(const struct syscallname *name,
diff --git a/linux-user/strace.list b/linux-user/strace.list
index fb9799e7e6..35c66e9fc8 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -218,13 +218,14 @@
 { TARGET_NR_fdatasync, "fdatasync" , "%s(%d)", NULL, NULL },
 #endif
 #ifdef TARGET_NR_fgetxattr
-{ TARGET_NR_fgetxattr, "fgetxattr" , NULL, NULL, NULL },
+{ TARGET_NR_fgetxattr, "fgetxattr" , NULL, print_fgetxattr, NULL },
 #endif
 #ifdef TARGET_NR_finit_module
 { TARGET_NR_finit_module, "finit_module" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_flistxattr
-{ TARGET_NR_flistxattr, "flistxattr" , NULL, NULL, NULL },
+{ TARGET_NR_flistxattr, "flistxattr" , NULL, print_flistxattr,
+                        print_syscall_ret_flistxattr},
 #endif
 #ifdef TARGET_NR_flock
 { TARGET_NR_flock, "flock" , NULL, NULL, NULL },
@@ -396,7 +397,7 @@
 { TARGET_NR_getuid32, "getuid32" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_getxattr
-{ TARGET_NR_getxattr, "getxattr" , NULL, NULL, NULL },
+{ TARGET_NR_getxattr, "getxattr" , NULL, print_getxattr, NULL },
 #endif
 #ifdef TARGET_NR_getxgid
 { TARGET_NR_getxgid, "getxgid" , NULL, NULL, NULL },
@@ -480,7 +481,7 @@
 { TARGET_NR_lchown32, "lchown32" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_lgetxattr
-{ TARGET_NR_lgetxattr, "lgetxattr" , NULL, NULL, NULL },
+{ TARGET_NR_lgetxattr, "lgetxattr" , NULL, print_lgetxattr, NULL },
 #endif
 #ifdef TARGET_NR_link
 { TARGET_NR_link, "link" , NULL, print_link, NULL },
@@ -495,10 +496,12 @@
 { TARGET_NR_listen, "listen" , "%s(%d,%d)", NULL, NULL },
 #endif
 #ifdef TARGET_NR_listxattr
-{ TARGET_NR_listxattr, "listxattr" , NULL, NULL, NULL },
+{ TARGET_NR_listxattr, "listxattr" , NULL, print_listxattr,
+                       print_syscall_ret_listxattr},
 #endif
 #ifdef TARGET_NR_llistxattr
-{ TARGET_NR_llistxattr, "llistxattr" , NULL, NULL, NULL },
+{ TARGET_NR_llistxattr, "llistxattr" , NULL, print_llistxattr,
+                        print_syscall_ret_llistxattr},
 #endif
 #ifdef TARGET_NR__llseek
 { TARGET_NR__llseek, "_llseek" , NULL, print__llseek, NULL },
-- 
2.17.1

Le 11/06/2020 à 17:51, Filip Bozuta a écrit :
> From: Filip Bozuta <Filip.Bozuta@syrmia.com>
> 
> This patch implements strace argument printing functionality for following syscalls:
> 
>     *getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value
> 
>         ssize_t getxattr(const char *path, const char *name, void *value, size_t size)
>         ssize_t lgetxattr(const char *path, const char *name, void *value, size_t size)
>         ssize_t fgetxattr(int fd, const char *name, void *value, size_t size)
>         man page: https://www.man7.org/linux/man-pages/man2/getxattr.2.html
> 
>     *listxattr, llistxattr, flistxattr - list extended attribute names
> 
>         ssize_t listxattr(const char *path, char *list, size_t size)
>         ssize_t llistxattr(const char *path, char *list, size_t size)
>         ssize_t flistxattr(int fd, char *list, size_t size)
>         man page: https://www.man7.org/linux/man-pages/man2/listxattr.2.html
> 
>     *removexattr, lremovexattr, fremovexattr - remove an extended attribute
> 
>          int removexattr(const char *path, const char *name)
>          int lremovexattr(const char *path, const char *name)
>          int fremovexattr(int fd, const char *name)
>          man page: https://www.man7.org/linux/man-pages/man2/removexattr.2.html

Compared to v2, fremovexattr, removexattr and lremovexattr are missing.

> 
> Implementation notes:
> 
>     All of the syscalls have strings as argument types and thus a separate
>     printing function was stated in file "strace.list" for every one of them.
>     All of these printing functions were defined in "strace.c" using existing
>     printing functions for appropriate argument types:
>        "print_string()" - for (const char*) type
>        "print_pointer()" - for (char*) and (void *) type
>        "print_raw_param()" for (int) and (size_t) type
>     Syscalls "getxattr()" and "lgetxattr()" have the same number and type of
>     arguments and thus their print functions ("print_getxattr", "print_lgetxattr")
>     share a same definition. The same statement applies to syscalls "listxattr()"
>     and "llistxattr()".
>     Function "print_syscall_ret_listxattr()" was added to print the returned list
>     of extended attributes for syscalls "print_listxattr(), print_llistxattr() and
>     print_flistxattr()".
> 
> Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
> ---
>  linux-user/strace.c    | 95 ++++++++++++++++++++++++++++++++++++++++++
>  linux-user/strace.list | 15 ++++---
>  2 files changed, 104 insertions(+), 6 deletions(-)
> 
> diff --git a/linux-user/strace.c b/linux-user/strace.c
> index 4f85606c19..a7c3ea8df3 100644
> --- a/linux-user/strace.c
> +++ b/linux-user/strace.c
> @@ -834,6 +834,41 @@ print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret,
>  }
>  #endif
>  
> +#if defined(TARGET_NR_listxattr) || defined(TARGET_NR_llistxattr) \
> + || defined(TARGGET_NR_flistxattr)
> +static void
> +print_syscall_ret_listxattr(const struct syscallname *name, abi_long ret,
> +                            abi_long arg0, abi_long arg1, abi_long arg2,
> +                            abi_long arg3, abi_long arg4, abi_long arg5)
> +{
> +    const char *errstr = NULL;
> +
> +    SYSCALL_RET_ERR(ret, errstr);
> +
> +    if (ret >= 0) {
> +        qemu_log(TARGET_ABI_FMT_ld, ret);
> +        qemu_log(" (list = ");
> +        if (arg1 != 0) {
> +            abi_long attr = arg1;
> +            while (target_strlen(attr) != 0) {

You can't rely on target_strlen(), you should rely on the value returned
by the ioctl() (ret) that is defined as the length of the returned data.

Thanks,
Laurent