[PATCH 2/3] linux-user: Add strace support for printing arguments of syscalls used to lock and unlock memory

[Filip Bozuta]

This patch implements strace argument printing functionality for following 
syscalls:

    * mlock, munlock, mlockall, munlockall - lock and unlock memory

       int mlock(const void *addr, size_t len)
       int munlock(const void *addr, size_t len)
       int mlockall(int flags)
       int munlockall(void)
       man page: https://man7.org/linux/man-pages/man2/mlock.2.html

Implementation notes:

    Syscall mlockall() takes an argument that is composed of predefined values
    which represent flags that determine the type of locking operation that is
    to be performed. For that reason, a printing function "print_mlockall" was
    stated in file "strace.list". This printing function uses an already 
existing
    function "print_flags()" to print the "flags" argument.  These flags are 
stated
    inside an array "mlockall_flags" that contains values of type "struct 
flags".
    These values are instantiated using an existing macro "FLAG_GENERIC()".
    The other syscalls have only primitive argument types, so the
    rest of the implementation was handled by stating an appropriate
    printing format in file "strace.list". Syscall mlock2() is not implemented 
in
    "syscall.c" and thus it's argument printing is not implemented in this 
patch.

Signed-off-by: Filip Bozuta <filip.boz...@syrmia.com>
---
 linux-user/strace.c    | 21 +++++++++++++++++++++
 linux-user/strace.list |  8 ++++----
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index dccfbc46e9..1fc4404310 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -1161,6 +1161,15 @@ UNUSED static struct flags falloc_flags[] = {
 #endif
 };
 
+UNUSED static struct flags mlockall_flags[] = {
+    FLAG_GENERIC(MCL_CURRENT),
+    FLAG_GENERIC(MCL_FUTURE),
+#ifdef MCL_ONFAULT
+    FLAG_GENERIC(MCL_ONFAULT),
+#endif
+    FLAG_END,
+};
+
 /*
  * print_xxx utility functions.  These are used to print syscall
  * parameters in certain format.  All of these have parameter
@@ -1939,6 +1948,18 @@ print_truncate(const struct syscallname *name,
 #define print_truncate64     print_truncate
 #endif
 
+#ifdef TARGET_NR_mlockall
+static void
+print_mlockall(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_flags(mlockall_flags, arg0, 1);
+    print_syscall_epilogue(name);
+}
+#endif
+
 #if defined(TARGET_NR_socket)
 static void
 print_socket(const struct syscallname *name,
diff --git a/linux-user/strace.list b/linux-user/strace.list
index 3b77b22daf..822b6be49c 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -567,13 +567,13 @@
 { TARGET_NR_mknodat, "mknodat" , NULL, print_mknodat, NULL },
 #endif
 #ifdef TARGET_NR_mlock
-{ TARGET_NR_mlock, "mlock" , NULL, NULL, NULL },
+{ TARGET_NR_mlock, "mlock" , "%s(%p," TARGET_FMT_lu ")", NULL, NULL },
 #endif
 #ifdef TARGET_NR_mlock2
 { TARGET_NR_mlock2, "mlock2" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_mlockall
-{ TARGET_NR_mlockall, "mlockall" , NULL, NULL, NULL },
+{ TARGET_NR_mlockall, "mlockall" , NULL, print_mlockall, NULL },
 #endif
 #ifdef TARGET_NR_mmap
 { TARGET_NR_mmap, "mmap" , NULL, print_mmap, print_syscall_ret_addr },
@@ -636,10 +636,10 @@
 { TARGET_NR_multiplexer, "multiplexer" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_munlock
-{ TARGET_NR_munlock, "munlock" , NULL, NULL, NULL },
+{ TARGET_NR_munlock, "munlock" , "%s(%p," TARGET_FMT_lu ")", NULL, NULL },
 #endif
 #ifdef TARGET_NR_munlockall
-{ TARGET_NR_munlockall, "munlockall" , NULL, NULL, NULL },
+{ TARGET_NR_munlockall, "munlockall" , "%s()", NULL, NULL },
 #endif
 #ifdef TARGET_NR_munmap
 { TARGET_NR_munmap, "munmap" , NULL, print_munmap, NULL },
-- 
2.17.1