[PATCH] S390: Sync ptrace.h with kernel. [BZ #21539]

[Stefan Liebler]

On 06/30/2017 12:09 PM, Florian Weimer wrote:
> On 06/19/2017 03:10 PM, Stefan Liebler wrote:
>>      	* sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c:
>>      	New file.
> 
> The test fails for me like this on s390x:
> 
> [root@ibm-z-25 build]# bash testrun.sh misc/tst-ptrace-singleblock
> cat /proc/23548/maps
> 80000000-80004000 r-xp 00000000 fd:00 1883202
> /root/build/misc/tst-ptrace-singleblock
> 80004000-80005000 r--p 00003000 fd:00 1883202
> /root/build/misc/tst-ptrace-singleblock
> 80005000-80006000 rw-p 00004000 fd:00 1883202
> /root/build/misc/tst-ptrace-singleblock
> 2aa00794000-2aa007ba000 r-xp 00000000 fd:00 34794498
> /root/build/elf/ld.so
> 2aa007ba000-2aa007bb000 r--p 00025000 fd:00 34794498
> /root/build/elf/ld.so
> 2aa007bb000-2aa007bd000 rw-p 00026000 fd:00 34794498
> /root/build/elf/ld.so
> 3fffd1e9000-3fffd1ea000 rw-s 00000000 00:04 146001
> /dev/zero (deleted)
> 3fffd1ea000-3fffd1ec000 rw-p 00000000 00:00 0
> 3fffd1ec000-3fffd38d000 r-xp 00000000 fd:00 34794501
> /root/build/libc.so
> 3fffd38d000-3fffd391000 r--p 001a0000 fd:00 34794501
> /root/build/libc.so
> 3fffd391000-3fffd393000 rw-p 001a4000 fd:00 34794501
> /root/build/libc.so
> 3fffd393000-3fffd39a000 rw-p 00000000 00:00 0
> 3ffffe62000-3fffff83000 rw-p 00000000 00:00 0
> [stack]
> child IA: 0x3fffd22ac62 last_break: 0x2aa0079e218
> error: ../sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c:111: not
> true: ptrace (req_singleblock, pid, NULL, NULL) == 0
> The PTRACE_SINGLEBLOCK of the tracer will stop after: brasl %r14,<puts@plt>!
> error: 1 test failures
> [root@ibm-z-25 build]#
> 
> Relevant package versions:
> 
> kernel-3.10.0-689.el7.s390x
> kernel-headers-3.10.0-689.el7.s390x
> devtoolset-6-gcc-6.3.1-3.1.el7.s390x
> 
> Please let me know if you need additional information to debug this.
> 
> Thanks,
> Florian
> 

Uuups. I also see this behaviour on a RHEL 7.3 machine.
We've checked that request 12 wasn't used in s390 kernel for other 
meanings as PTRACE_SINGLEBLOCK. But we've missed the fact, that it has 
been introduced with kernel 3.15. On older kernels -1 is returned with 
errno EIO.

Please have a look at the attached patch. I've adjusted the test:

Now ptrace request 12 is first done with data argument pointing to
a buffer:
-If request 12 is interpreted as PTRACE_GETREGS, it will store the regs
to buffer without an error. Here the test expects that the buffer is
untouched and an error is returned.

-If request 12 is interpreted as PTRACE_SINGLEBLOCK, it will fail
as data argument is no valid signal.

-If request 12 is not implemented, it will also fail.


Afterwards the request 12 is done with zero data argument:
-If the kernel has support for PTRACE_SINGLEBLOCK (then the kernel
header asm/ptrace.h defines this macro), the ptrace call is not allowed
to fail and has to continue the tracee until next taken branch.

-If the kernel has no support for PTRACE_SINGLEBLOCK, the ptrace call
has to fail with EIO. Then I continue the tracee with PTRACE_CONT.

-If the request 12 is interpreted as PTRACE_GETREGS, it will fail too.
It fails with EFAULT on intel / power as data argument is NULL.
According to the man-page: "Unfortunately, under Linux, different
variations of this fault will return EIO or EFAULT more or less
arbitrarily".
But if request 12 is interpreted as PTRACE_GETREGS, the first ptrace
call will touch the buffer which is detected by this test.

Any thoughts?
If this change is okay, I'll commit it.

Thanks.
Stefan


ChangeLog:

	* sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c:
	Support running on kernels without PTRACE_SINGLEBLOCK.
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