linux-user: Extend strace support to enable argument printing after syscall execution
Structure "struct syscallname" in file "strace.c" is used for "-strace"
to print arguments and return values of syscalls. The last field of
this structure "result" represents the calling function that prints the
return values. This field was extended in this patch so that this function
takes all syscalls arguments beside the return value. In this way, it enables
"-strace" to print arguments of syscalls that have changed after the syscall
execution. This extension will be useful as there are many syscalls that
return values inside their arguments (i.e. listxattr() that returns the list
of extended attributes inside the "list" argument).
Implementation notes:
Since there are already three existing "print_syscall_ret*" functions inside
"strace.c" ("print_syscall_ret_addr()", "print_syscall_ret_adjtimex()",
"print_syscall_ret_newselect()"), they were changed to have all syscall arguments
beside the return value. This was done so that these functions don't cause build
errors (even though syscall arguments are not used in these functions).
There is code repetition in these functions for checking the return value
and printing the approppriate error message (this code is also located in
print_syscall_ret() at the end of "strace.c"). That is the reason why a
function "syscall_print_err()" was added for this code and put inside these
functions. Functions "print_newselect()" and "print_syscall_ret_newselect()"
were changed to use this new implemented functionality and not store the syscall
argument values in separate static variables.
Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200619123331.17387-2-filip.bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 17ed7f8..1b971c0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -12565,7 +12565,7 @@
arg5, arg6, arg7, arg8);
if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
- print_syscall_ret(num, ret);
+ print_syscall_ret(num, ret, arg1, arg2, arg3, arg4, arg5, arg6);
}
record_syscall_return(cpu, num, ret);
