Re: ATF tests hanging

[Martin Husemann <martin%duskware.de@localhost>]

On Wed, Dec 27, 2017 at 02:51:38PM +0100, Martin Husemann wrote:
> On Wed, Dec 27, 2017 at 08:42:52AM -0500, Christos Zoulas wrote:
> > Well, it is not failing on sparc64, that's the issue.
> 
> It is not expected to fail, but it is failing. The tracer process waits
> for the child but the child does not exit - maybe the PT_CONTINUE did
> not work or whatever.

I am trying to understand what the test does. It still makes no sense to
me and I completely fail to see how it can work anywhere.

The test forks a child process and then:

	child:
	 - ptrace(PT_TRACE_ME...)
	 - blocks SIGTRAP
	 - raises SIGSTOP
	 - does a MD breakpoint instruction
	 - exits

apparently after assuming the tracing (parent) process has skipped the
breakpoint instruction.

	parent:
	 - waits for the child process to notify it of the SIGSTOP signal
	 - ptrace(PT_CONTINUE, ..., (void *)1, ..)

that is: continue where it left of, i.e. right on the breakpoint
instruction. A real debugger would have removed the breakpoint
instruction and replaced it by the original code (or suply a new value
for %pc as address argument), but in this test this does not happen, so
the child should hit a breakpoint right away again.

I must be missing something, or the test works on alpha and x86 due to a
bug, but correctly fails on other architectures.

Martin