[v3,4/6] linux-user: Add strace support for printing arguments of lseek()

Commit Message

Filip Bozuta June 11, 2020, 3:51 p.m. UTC

From: Filip Bozuta <[e-mail]>

This patch implements strace argument printing functionality for syscall:

    *lseek - reposition read/write file offset

         off_t lseek(int fd, off_t offset, int whence)
         man page: https://www.man7.org/linux/man-pages/man2/lseek.2.html

Implementation notes:

    The syscall's third argument "whence" has predefined values:
    "SEEK_SET","SEEK_CUR","SEEK_END","SEEK_DATA","SEEK_HOLE"
    and thus a separate printing function "print_lseek" was stated
    in file "strace.list". This function is defined in "strace.c"
    by using an existing function "print_raw_param()" to print
    the first and second argument and a switch(case) statement
    for the predefined values of the third argument.
    Values "SEEK_DATA" and "SEEK_HOLE" are defined in kernel version 3.1.
    That is the reason why case statements for these values are
    enwrapped in #ifdef directive.

Signed-off-by: Filip Bozuta <[e-mail]>
Reviewed-by: Laurent Vivier <[e-mail]>
---
 linux-user/strace.c    | 31 +++++++++++++++++++++++++++++++
 linux-user/strace.list |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)

Patch

diff --git a/linux-user/strace.c b/linux-user/strace.c
index a7c3ea8df3..ee73ff575c 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -1815,6 +1815,37 @@  print__llseek(const struct syscallname *name,
 }
 #endif
 
+#ifdef TARGET_NR_lseek
+static void
+print_lseek(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_raw_param(TARGET_ABI_FMT_ld, arg1, 0);
+    switch (arg2) {
+    case SEEK_SET:
+        qemu_log("SEEK_SET"); break;
+    case SEEK_CUR:
+        qemu_log("SEEK_CUR"); break;
+    case SEEK_END:
+        qemu_log("SEEK_END"); break;
+#ifdef SEEK_DATA
+    case SEEK_DATA:
+        qemu_log("SEEK_DATA"); break;
+#endif
+#ifdef SEEK_HOLE
+    case SEEK_HOLE:
+        qemu_log("SEEK_HOLE"); break;
+#endif
+    default:
+        print_raw_param("%#x", arg2, 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 35c66e9fc8..63e150736e 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -516,7 +516,7 @@ 
 { TARGET_NR_lremovexattr, "lremovexattr" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_lseek
-{ TARGET_NR_lseek, "lseek" , NULL, NULL, NULL },
+{ TARGET_NR_lseek, "lseek" , NULL, print_lseek, NULL },
 #endif
 #ifdef TARGET_NR_lsetxattr
 { TARGET_NR_lsetxattr, "lsetxattr" , NULL, NULL, NULL },