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ptrace.2: Clarify the purpose of mentioning the kernel PTRACE_MODE_* constants 

The "ptrace access mode" text is about user-space-visible
behavior, but in order to explain that behavior at what I
believe is a sufficient level of detail (e.g., to differentiate
the various types of checks that are performed for various
system calls and pseudofile accesses), one needs (1) to discuss
the MODE flag details as implemented in the kernel, and (2) to
have a shorthand way to refer to the various cases from other
pages. It's not absolutely necessary to name the flags for (1),
but using the flag names is certainly a handy shorthand for (2).

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2016-06-22 20:41:15 +02:00
parent 6f92213776
commit e4e2367fe6
1 changed files with 11 additions and 0 deletions
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@ -2115,6 +2115,17 @@ or calling
.RB ( PTRACE_MODE_ATTACH
was effectively the default before Linux 2.6.27.)
.PP
Note that all of the
.BR PTRACE_MODE_*
constants described in this subsection are kernel-internal,
and not visible to user space.
The constant names are mentioned here in order to label the various kinds of
ptrace access mode checks that are performed for various system calls
and accesses to various pseudofiles (e.g., under
.IR /proc ).
These names are used in other man pages to provide a simple
shorthand for labeling the different kernel checks.
Since Linux 4.5,
.\" commit caaee6234d05a58c5b4d05e7bf766131b810a657
the above access mode checks may be combined (ORed) with