Re: [PATCH v3 6/6] linux-user: Add strace support for printing arguments of fallocate()

[Filip Bozuta]

On 15.6.20. 13:58, Laurent Vivier wrote:
> Le 11/06/2020 à 17:51, Filip Bozuta a écrit :
>> From: Filip Bozuta <Filip.Bozuta@syrmia.com>
>>
>> This patch implements strace argument printing functionality for following 
>> syscall:
>>
>>      *fallocate - manipulate file space
>>
>>          int fallocate(int fd, int mode, off_t offset, off_t len)
>>          man page: https://www.man7.org/linux/man-pages/man2/fallocate.2.html
>>
>> Implementation notes:
>>
>>      This syscall's second argument "mode" is composed of predefined values
>>      which represent flags that determine the type of operation that is
>>      to be performed on the file space. For that reason, a printing
>>      function "print_fallocate" was stated in file "strace.list". This 
>> printing
>>      function uses an already existing function "print_flags()" to print 
>> flags of
>>      the "mode" argument. These flags are stated inside an array 
>> "falloc_flags"
>>      that contains values of type "struct flags". These values are 
>> instantiated
>>      using an existing macro "FLAG_GENERIC()". Most of these flags are 
>> defined
>>      after kernel version 3.0 which is why they are enwrapped in an #ifdef
>>      directive.
>>      The syscall's third ant fourth argument are of type "off_t" which can
>>      cause variations between 32/64-bit architectures. To handle this 
>> variation,
>>      function "target_offset64()" was copied from file "strace.c" and used in
>>      "print_fallocate" to print "off_t" arguments for 32-bit architectures.
>>
>> Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
>> Reviewed-by: Laurent Vivier <laurent@vivier.eu>
>> ---
>>   linux-user/qemu.h      | 16 ++++++++++++++++
>>   linux-user/strace.c    | 40 ++++++++++++++++++++++++++++++++++++++++
>>   linux-user/strace.list |  2 +-
>>   linux-user/syscall.c   | 16 ----------------
>>   4 files changed, 57 insertions(+), 17 deletions(-)
>>
>> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
>> index 8f938b8105..be67391ba4 100644
>> --- a/linux-user/qemu.h
>> +++ b/linux-user/qemu.h
>> @@ -670,6 +670,22 @@ static inline int is_error(abi_long ret)
>>       return (abi_ulong)ret >= (abi_ulong)(-4096);
>>   }
>>   
>> +#if TARGET_ABI_BITS == 32
>> +static inline uint64_t target_offset64(uint32_t word0, uint32_t word1)
>> +{
>> +#ifdef TARGET_WORDS_BIGENDIAN
>> +    return ((uint64_t)word0 << 32) | word1;
>> +#else
>> +    return ((uint64_t)word1 << 32) | word0;
>> +#endif
>> +}
>> +#else /* TARGET_ABI_BITS == 32 */
>> +static inline uint64_t target_offset64(uint64_t word0, uint64_t word1)
>> +{
>> +    return word0;
>> +}
>> +#endif /* TARGET_ABI_BITS != 32 */
>> +
>>   /**
>>    * preexit_cleanup: housekeeping before the guest exits
>>    *
>> diff --git a/linux-user/strace.c b/linux-user/strace.c
>> index 40c17f7abe..5f370256e3 100644
>> --- a/linux-user/strace.c
>> +++ b/linux-user/strace.c
>> @@ -1144,6 +1144,26 @@ UNUSED static struct flags statx_mask[] = {
>>       FLAG_END,
>>   };
>>   
>> +UNUSED static struct flags falloc_flags[] = {
>> +    FLAG_GENERIC(FALLOC_FL_KEEP_SIZE),
>> +    FLAG_GENERIC(FALLOC_FL_PUNCH_HOLE),
>> +#ifdef FALLOC_FL_NO_HIDE_STALE
>> +    FLAG_GENERIC(FALLOC_FL_NO_HIDE_STALE),
>> +#endif
>> +#ifdef FALLOC_FL_COLLAPSE_RANGE
>> +    FLAG_GENERIC(FALLOC_FL_COLLAPSE_RANGE),
>> +#endif
>> +#ifdef FALLOC_FL_ZERO_RANGE
>> +    FLAG_GENERIC(FALLOC_FL_ZERO_RANGE),
>> +#endif
>> +#ifdef FALLOC_FL_INSERT_RANGE
>> +    FLAG_GENERIC(FALLOC_FL_INSERT_RANGE),
>> +#endif
>> +#ifdef FALLOC_FL_UNSHARE_RANGE
>> +    FLAG_GENERIC(FALLOC_FL_UNSHARE_RANGE),
>> +#endif
>> +};
>> +
>>   /*
>>    * print_xxx utility functions.  These are used to print syscall
>>    * parameters in certain format.  All of these have parameter
>> @@ -1561,6 +1581,26 @@ print_faccessat(const struct syscallname *name,
>>   }
>>   #endif
>>   
>> +#ifdef TARGET_NR_fallocate
>> +static void
>> +print_fallocate(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_flags(falloc_flags, arg1, 0);
>> +#if TARGET_ABI_BITS == 32
>> +    print_raw_param("%ld", target_offset64(arg2, arg3), 0);
>> +    print_raw_param("%ld", target_offset64(arg4, arg5), 1);
>> +#else
>> +    print_raw_param("%ld", arg2, 0);
>> +    print_raw_param("%ld", arg3, 1);
>> +#endif
>>
> You have removed the PRIu64 and TARGET_ABI_FMT_ld from the v2. So my
> Reviewed-by is not relevant for the v3.

I am sorry. Something wen't wrong (not sure what...) when I used git 
rebase and it removed some changes from v2

(including the ones with removexattr, lremovexattr, fremovexattr)

This was an irresponsible mistake by my part and I will of course 
correct this in v4 and make sure to thoroughly check my

patches before sending them so that this doesn't happen again.

Just wanted to let you know that I didn't do this on purpose.

>
> Thanks,
> Laurent