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From: Okash Khawaja <okash.khawaja@gmail.com>
To: kernelnewbies <kernelnewbies@kernelnewbies.org>
Subject: Purpose of PTRACE_SETSIGINFO for x86
Date: Fri, 14 Dec 2018 22:30:42 +0000	[thread overview]
Message-ID: <CAOtcWM0YxqvZecP1SOvBLRn3ZNaSg2idicDuG0Fg-4ekVe02OA@mail.gmail.com> (raw)

Hi,

What does the PTRACE_SETSIGINFO ptrace command do?

I can see in kernel/ptrace.c:ptrace_request() it calls
ptrace_setsiginfo(), passing it the child's (tracee's) task descriptor
and siginfo_t instance originally passed in from user space.

ptrace_setsiginfo() sets child's last_siginfo to the siginfo_t
instance passed in. Now there are only two places where a
child->last_siginfo's value is read are in kernel/ptrace.c:

1. by the ptrace command PTRACE_GETSIGINFO
2. by the ptrace command PTRACE_LISTEN

There doesn't seem to be a place where value of last_siginfo is read
by signal handling code. There is however this comment in
kernel/signal.c:ptrace_signal():

/*
 * Update the siginfo structure if the signal has
 * changed.  If the debugger wanted something
 * specific in the siginfo structure then it should
 * have updated *info via PTRACE_SETSIGINFO.
 */

Where does PTRACE_SETSIGINFO update *info?

Thanks,
Okash

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                 reply	other threads:[~2018-12-14 22:32 UTC|newest]

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