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ptrace.2: Add information on PTRACE_SEIZE versus PTRACE_ATTACH differences 

Extend description of PTRACE_SEIZE with the short summary of its
differences from PTRACE_ATTACH.

The following paragraph:

PTRACE_EVENT_STOP
       Stop induced by PTRACE_INTERRUPT command, or group-stop, or ini-
       tial  ptrace-stop when a new child is attached (only if attached
       using PTRACE_SEIZE), or PTRACE_EVENT_STOP if PTRACE_SEIZE was used.

has an editing error (the part after last comma makes no sense).
Removing it.

Mention that legacy post-execve SIGTRAP is disabled by PTRACE_SEIZE.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Denys Vlasenko 2015-02-11 14:20:35 +01:00 committed by Michael Kerrisk
parent 0e48cd5a7c
commit 28e2ca574f
1 changed files with 33 additions and 8 deletions
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41
man2/ptrace.2
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@ -781,6 +781,23 @@ Unlike
.BR PTRACE_ATTACH ,
.B PTRACE_SEIZE
does not stop the process.
Group-stops are reported as
.B PTRACE_EVENT_STOP
with
.I WSTOPSIG(status)
== stopping_signal.
Automatically attached children stop with
.B PTRACE_EVENT_STOP
with
.I WSTOPSIG(status)
==
.B SIGTRAP
instead of having
.B SIGSTOP
signal delivered to them.
.BR evecve (2)
does not deliver an extra
.BR SIGTRAP.
Only a
.BR PTRACE_SEIZE d
process can accept
@ -788,6 +805,12 @@ process can accept
and
.B PTRACE_LISTEN
commands.
The "seized" behavior just described is inherited by
children that are automatically attached using
.BR PTRACE_O_TRACEFORK ,
.BR PTRACE_O_TRACEVFORK ,
and
.BR PTRACE_O_TRACECLONE .
.I addr
must be zero.
.I data
@ -1337,12 +1360,7 @@ Stop induced by
.B PTRACE_INTERRUPT
command, or group-stop, or initial ptrace-stop when a new child is attached
(only if attached using
.BR PTRACE_SEIZE ),
or
.B PTRACE_EVENT_STOP
if
.B PTRACE_SEIZE
was used.
.BR PTRACE_SEIZE ).
.TP
.B PTRACE_EVENT_SECCOMP
Stop triggered by a
@ -1837,7 +1855,12 @@ If the
.B PTRACE_O_TRACEEXEC
option is
.I not
in effect for the execing tracee, the kernel delivers an extra
in effect for the execing tracee,
and if tracee was
.BR PTRACE_ATTACH ed
rather that
.BR PTRACE_SEIZE d,
the kernel delivers an extra
.B SIGTRAP
to the tracee after
.BR execve (2)
@ -1870,7 +1893,9 @@ However, determining
to suppress is not easy.
Setting the
.B PTRACE_O_TRACEEXEC
option and thus suppressing this extra
option or using
.B PTRACE_SEIZE
and thus suppressing this extra
.B SIGTRAP
is the recommended approach.
.SS Real parent