Re: [PATCH v2] linux-user: Fix strace output for s390x mmap()

[iii <iii@imap.linux.ibm.com>]

On 2024-11-21 11:07, Philippe Mathieu-Daudé wrote:
> On 21/11/24 10:26, iii wrote:
>> On 2024-11-21 10:00, Philippe Mathieu-Daudé wrote:
>>> On 20/11/24 22:26, Ilya Leoshkevich wrote:
>>>> print_mmap() assumes that mmap() receives arguments via memory if
>>>> mmap2() is present. s390x (as opposed to s390) does not fit this
>>>> pattern: it does not have mmap2(), but mmap() still receives 
>>>> arguments
>>>> via memory.
>>>> 
>>>> Fix by sharing the detection logic between syscall.c and strace.c.
>>>> 
>>>> Cc: qemu-stable@nongnu.org
>>>> Fixes: d971040c2d16 ("linux-user: Fix strace output for old_mmap")
>>>> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
>>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>>> ---
>>>> 
>>>> v1: 
>>>> https://lore.kernel.org/qemu-devel/20241119211138.148806-1-iii@linux.ibm.com/
>>>> v1 -> v2: Share the detection logic between syscall.c and strace.c
>>>>            (Richard).
>>>> 
>>>>   linux-user/strace.c       | 2 +-
>>>>   linux-user/syscall.c      | 5 +----
>>>>   linux-user/syscall_defs.h | 7 +++++++
>>>>   3 files changed, 9 insertions(+), 5 deletions(-)
>>>> 
>>>> diff --git a/linux-user/strace.c b/linux-user/strace.c
>>>> index b70eadc19ef..9c55f39b095 100644
>>>> --- a/linux-user/strace.c
>>>> +++ b/linux-user/strace.c
>>>> @@ -3971,7 +3971,7 @@ print_mmap(CPUArchState *cpu_env, const struct 
>>>> syscallname *name,
>>>>   {
>>>>       return print_mmap_both(cpu_env, name, arg0, arg1, arg2, arg3,
>>>>                              arg4, arg5,
>>>> -#if defined(TARGET_NR_mmap2)
>>>> +#ifdef TARGET_ARCH_WANT_SYS_OLD_MMAP
>>> 
>>> We still want to print for mmap2, so:
>>> 
>>>   #if defined(TARGET_NR_mmap2) || 
>>> defined(TARGET_ARCH_WANT_SYS_OLD_MMAP)
>>> 
>>>>                               true
>>>>   #else
>>>>                               false
>> 
>> mmap2() has its own flow from what I can see:
>> 
>> print_mmap2()
>>    print_mmap_both(..., is_old_mmap=false)
>> 
>> It should not call print_mmap(), which I'm changing here.
>> 
>> [...]
> 
> If so, better to clean that in a previous patch.

Sorry, I'm confused. What previous patch are you referring to?

> Cc'ing Helge since I'm a bit confused by commit d971040c2d intent
> ("linux-user: Fix strace output for old_mmap").

My understanding of the Helge's idea is that "defined(TARGET_NR_mmap2)" 
is
true if, and only if, mmap() takes arguments via memory.