Bug #1528

ktrace does not show proper return values for pipe(2)

Added by corecode about 5 years ago. Updated 9 months ago.

Status:In ProgressStart date:
Priority:NormalDue date:
Assignee:tuxillo% Done:

0%

Category:Kernel
Target version:3.8.0

Description

When ktracing a pipe syscall, the output is:

57705 a.out CALL pipe
57705 a.out RET pipe 3

However, the return value of pipe is 0, and the returned value for the
file descs is {3, 4}.

History

#1 Updated by Anonymous about 5 years ago

I've added a kprintf in ktrsysret() and here is what printed:

1126 a.out CALL pipe
1126 a.out RET ret=3 error=0 code=42 pipe 3

Question is why `ret' contains the first file descriptor of the pair at all.
(and not zero as ought to)

Stathis

#2 Updated by corecode about 5 years ago

Stathis Kamperis (via DragonFly issue tracker) wrote:
> Stathis Kamperis <> added the comment:
>
> I've added a kprintf in ktrsysret() and here is what printed:
>
> 1126 a.out CALL pipe
> 1126 a.out RET ret=3 error=0 code=42 pipe 3
>
> Question is why `ret' contains the first file descriptor of the pair at all.
> (and not zero as ought to)

This is because sys_pipe returns both fds as return value, namely
sysmsg_fds[0] and sysmsg_fds[1]. However ktrsysret is only called with
sysmsg_result, which covers only the first fd.

I guess the pipe libc glue code copies this result into the array.

cheers
simon

#3 Updated by tuxillo 9 months ago

  • Description updated (diff)
  • Category set to Kernel
  • Status changed from New to In Progress
  • Assignee changed from 0 to tuxillo
  • Target version set to 3.8.0

Grab.

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