Re: [PATCH v5 1/6] linux-user: Extend strace support to enable argument printing after syscall execution

[Laurent Vivier]

Le 19/06/2020 à 14:33, Filip Bozuta a écrit :
> From: Filip Bozuta <Filip.Bozuta@syrmia.com>
> 
>     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>
> ---
>  linux-user/qemu.h    |   4 +-
>  linux-user/strace.c  | 110 ++++++++++++++++++++++---------------------
>  linux-user/syscall.c |   2 +-
>  3 files changed, 61 insertions(+), 55 deletions(-)
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>