[v3] linux-user: Trace sendto/recvfrom

[PATCH v3 5/5] linux-user: Add strace for recvfrom()

Posted by Philippe Mathieu-Daudé 3 months, 2 weeks ago

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 linux-user/strace.c    | 19 +++++++++++++++++++
 linux-user/strace.list |  2 +-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index 98ef26b917..d76907fdc9 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -3127,6 +3127,25 @@ print_bind(CPUArchState *cpu_env, const struct syscallname *name,
 }
 #endif
 
+#ifdef TARGET_NR_recvfrom
+static void
+print_recvfrom(CPUArchState *cpu_env, const struct syscallname *name,
+               abi_long arg0, abi_long arg1, abi_long arg2,
+               abi_long arg3, abi_long arg4, abi_long arg5)
+{
+    abi_ulong addrlen;
+
+    get_user_ualx(addrlen, arg5, 0);
+
+    print_syscall_prologue(name);
+    print_sockfd(arg0, 0);
+    print_buf_len(arg1, arg2, 0);
+    print_flags(msg_flags, arg3, 0);
+    print_sockaddr(arg4, addrlen, 1);
+    print_syscall_epilogue(name);
+}
+#endif
+
 #ifdef TARGET_NR_sendto
 static void
 print_sendto(CPUArchState *cpu_env, const struct syscallname *name,
diff --git a/linux-user/strace.list b/linux-user/strace.list
index 5a86419e7d..77ca824f9c 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -1135,7 +1135,7 @@
 { TARGET_NR_recv, "recv" , "%s(%d,%p,%u,%d)", NULL, NULL },
 #endif
 #ifdef TARGET_NR_recvfrom
-{ TARGET_NR_recvfrom, "recvfrom" , NULL, NULL, NULL },
+{ TARGET_NR_recvfrom, "recvfrom" , NULL, print_recvfrom, NULL },
 #endif
 #ifdef TARGET_NR_recvmmsg
 { TARGET_NR_recvmmsg, "recvmmsg" , NULL, NULL, NULL },
-- 
2.45.2

Re: [PATCH v3 5/5] linux-user: Add strace for recvfrom()

Posted by Ilya Leoshkevich 1 month, 3 weeks ago

On Wed, 2024-08-07 at 14:43 +0200, Philippe Mathieu-Daudé wrote:
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  linux-user/strace.c    | 19 +++++++++++++++++++
>  linux-user/strace.list |  2 +-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-user/strace.c b/linux-user/strace.c
> index 98ef26b917..d76907fdc9 100644
> --- a/linux-user/strace.c
> +++ b/linux-user/strace.c
> @@ -3127,6 +3127,25 @@ print_bind(CPUArchState *cpu_env, const struct
> syscallname *name,
>  }
>  #endif
>  
> +#ifdef TARGET_NR_recvfrom
> +static void
> +print_recvfrom(CPUArchState *cpu_env, const struct syscallname
> *name,
> +               abi_long arg0, abi_long arg1, abi_long arg2,
> +               abi_long arg3, abi_long arg4, abi_long arg5)
> +{
> +    abi_ulong addrlen;
> +
> +    get_user_ualx(addrlen, arg5, 0);
> +
> +    print_syscall_prologue(name);
> +    print_sockfd(arg0, 0);
> +    print_buf_len(arg1, arg2, 0);
> +    print_flags(msg_flags, arg3, 0);
> +    print_sockaddr(arg4, addrlen, 1);
> +    print_syscall_epilogue(name);
> +}
> +#endif
> +
>  #ifdef TARGET_NR_sendto
>  static void
>  print_sendto(CPUArchState *cpu_env, const struct syscallname *name,
> diff --git a/linux-user/strace.list b/linux-user/strace.list
> index 5a86419e7d..77ca824f9c 100644
> --- a/linux-user/strace.list
> +++ b/linux-user/strace.list
> @@ -1135,7 +1135,7 @@
>  { TARGET_NR_recv, "recv" , "%s(%d,%p,%u,%d)", NULL, NULL },
>  #endif
>  #ifdef TARGET_NR_recvfrom
> -{ TARGET_NR_recvfrom, "recvfrom" , NULL, NULL, NULL },
> +{ TARGET_NR_recvfrom, "recvfrom" , NULL, print_recvfrom, NULL },
>  #endif
>  #ifdef TARGET_NR_recvmmsg
>  { TARGET_NR_recvmmsg, "recvmmsg" , NULL, NULL, NULL },

I needed to implement read()/write() tracing and stumbled upon this
series, which overall looks like a good thing to have. I spotted a few
issues though.


I get the following build error:

qemu/linux-user/strace.c:3138:5: error: implicit declaration of
function ‘get_user_ualx’; did you mean ‘get_user_ual’? [-Wimplicit-
function-declaration]
 3138 |     get_user_ualx(addrlen, arg5, 0);
      |     ^~~~~~~~~~~~~
      |     get_user_ual


The following helps:

--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -2666,11 +2666,15 @@ static void print_sockfd(abi_long sockfd, int
last)
 
 #endif
 
-#if defined(TARGET_NR_socketcall)
+#if defined(TARGET_NR_socketcall) || defined(TARGET_NR_recvfrom)
 
 #define get_user_ualx(x, gaddr, idx) \
         get_user_ual(x, (gaddr) + (idx) * sizeof(abi_long))
 
+#endif
+
+#if defined(TARGET_NR_socketcall)
+
 static void do_print_socket(const char *name, abi_long arg1)
 {
     abi_ulong domain, type, protocol;


With this I get the following output, which w.r.t. its shape looks
good:

598730 recvfrom(3,"HTTP/1.1 400 Bad request\15\12Connection:
Cl"...,8192,0,{sa_family=0, sa_data={00, 00, 00, 00, 00, 00, 00, 00,
00, 00, 00, 00, 00, 00}},128) = 0

However: aren't we printing the contents of the buffer before the
syscall returns? Same with sockaddr. This would make the output not
very useful.

Re: [PATCH v3 5/5] linux-user: Add strace for recvfrom()

Posted by Richard Henderson 1 month, 2 weeks ago

On 10/1/24 23:55, Ilya Leoshkevich wrote:
> On Wed, 2024-08-07 at 14:43 +0200, Philippe Mathieu-Daudé wrote:
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   linux-user/strace.c    | 19 +++++++++++++++++++
>>   linux-user/strace.list |  2 +-
>>   2 files changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/linux-user/strace.c b/linux-user/strace.c
>> index 98ef26b917..d76907fdc9 100644
>> --- a/linux-user/strace.c
>> +++ b/linux-user/strace.c
>> @@ -3127,6 +3127,25 @@ print_bind(CPUArchState *cpu_env, const struct
>> syscallname *name,
>>   }
>>   #endif
>>   
>> +#ifdef TARGET_NR_recvfrom
>> +static void
>> +print_recvfrom(CPUArchState *cpu_env, const struct syscallname
>> *name,
>> +               abi_long arg0, abi_long arg1, abi_long arg2,
>> +               abi_long arg3, abi_long arg4, abi_long arg5)
>> +{
>> +    abi_ulong addrlen;
>> +
>> +    get_user_ualx(addrlen, arg5, 0);
>> +
>> +    print_syscall_prologue(name);
>> +    print_sockfd(arg0, 0);
>> +    print_buf_len(arg1, arg2, 0);
>> +    print_flags(msg_flags, arg3, 0);
>> +    print_sockaddr(arg4, addrlen, 1);
>> +    print_syscall_epilogue(name);
>> +}
>> +#endif
>> +
>>   #ifdef TARGET_NR_sendto
>>   static void
>>   print_sendto(CPUArchState *cpu_env, const struct syscallname *name,
>> diff --git a/linux-user/strace.list b/linux-user/strace.list
>> index 5a86419e7d..77ca824f9c 100644
>> --- a/linux-user/strace.list
>> +++ b/linux-user/strace.list
>> @@ -1135,7 +1135,7 @@
>>   { TARGET_NR_recv, "recv" , "%s(%d,%p,%u,%d)", NULL, NULL },
>>   #endif
>>   #ifdef TARGET_NR_recvfrom
>> -{ TARGET_NR_recvfrom, "recvfrom" , NULL, NULL, NULL },
>> +{ TARGET_NR_recvfrom, "recvfrom" , NULL, print_recvfrom, NULL },
>>   #endif
>>   #ifdef TARGET_NR_recvmmsg
>>   { TARGET_NR_recvmmsg, "recvmmsg" , NULL, NULL, NULL },
> 
> I needed to implement read()/write() tracing and stumbled upon this
> series, which overall looks like a good thing to have. I spotted a few
> issues though.
> 
> 
> I get the following build error:
> 
> qemu/linux-user/strace.c:3138:5: error: implicit declaration of
> function ‘get_user_ualx’; did you mean ‘get_user_ual’? [-Wimplicit-
> function-declaration]
>   3138 |     get_user_ualx(addrlen, arg5, 0);
>        |     ^~~~~~~~~~~~~
>        |     get_user_ual
> 
> 
> The following helps:
> 
> --- a/linux-user/strace.c
> +++ b/linux-user/strace.c
> @@ -2666,11 +2666,15 @@ static void print_sockfd(abi_long sockfd, int
> last)
>   
>   #endif
>   
> -#if defined(TARGET_NR_socketcall)
> +#if defined(TARGET_NR_socketcall) || defined(TARGET_NR_recvfrom)
>   
>   #define get_user_ualx(x, gaddr, idx) \
>           get_user_ual(x, (gaddr) + (idx) * sizeof(abi_long))
>   
> +#endif
> +
> +#if defined(TARGET_NR_socketcall)

Or just not use get_user_ualx.

> However: aren't we printing the contents of the buffer before the
> syscall returns? Same with sockaddr. This would make the output not
> very useful.

Yes indeed.  Two of the three pointers are output buffers; the last is in/out.


r~

[PATCH v3 1/5] linux-user: Correct print_sockaddr() format
[PATCH v3 2/5] linux-user: Display sockaddr buffer as pointer
[PATCH v3 3/5] linux-user: Factor print_buf_len() out
[PATCH v3 4/5] linux-user: Add strace for sendto()
[PATCH v3 5/5] linux-user: Add strace for recvfrom()