On Fri, Dec 07, 2018 at 10:12:49PM +1100, Michael Ellerman wrote:

"Dmitry V. Levin" [off-list ref] writes:

quoted

On Mon, Dec 03, 2018 at 06:18:23AM +0300, Dmitry V. Levin wrote:

quoted

From: Elvira Khabirova <redacted>

Arch code should use tracehook_*() helpers, as documented
in include/linux/tracehook.h,
ptrace_report_syscall() is not expected to be used outside that file.

Co-authored-by: Dmitry V. Levin [off-list ref]
Fixes: 5521eb4bca2d ("powerpc/ptrace: Add support for PTRACE_SYSEMU")
Signed-off-by: Elvira Khabirova <redacted>
Signed-off-by: Dmitry V. Levin <redacted>
---
v4: rewritten to call tracehook_report_syscall_entry() once, compile-tested
v3: add a descriptive comment
v2: explicitly ignore tracehook_report_syscall_entry() return code

 arch/powerpc/kernel/ptrace.c | 54 +++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 19 deletions(-)

Sorry, this patch does not work, please ignore it.

Hmm OK. Why exactly?

Unfortunately, I have no idea why it doesn't work.
All I can say is it breaks strace because the kernel no longer sends
syscall entry stops.

I wrote more or less the same patch, although I used a temporary bool.

quoted

However, the bug blocks PTRACE_GET_SYSCALL_INFO, so please fix it.

Sorry, didn't realise it was blocking you.

We are changing ptrace_report_syscall signature to implement
PTRACE_GET_SYSCALL_INFO, and this is the only place in the kernel besides
tracehook_report_syscall_*() that invokes ptrace_report_syscall() directly.

quoted

I'm going to use
	if (tracehook_report_syscall_entry(regs))
		return -1;
	return -1;
in the series until you have a better fix.

Yeah that's fine by me. I could send that to Linus for 4.20 if you want
me to, otherwise I'm fine for you to carry it in your series.

Yes, please.  I'll send a v5 shortly.


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