Michael Kerrisk [Tue, 25 Jun 2019 04:40:21 +0000 (06:40 +0200)]
ipc.5: Remove old link to svipc.7/sysvipc.7 page
Long ago, the sysvipc.7 page was called ipc.5, which was both a
misnaming (too general a name) and an inconsistent section. The
page was renamed (to svipc.7) many years ago, and the link with
the old name has probably ceased to be needed. So, remove it.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
if (*xp != INIT_VALUE)
printf("It looks like the variable passed to the exit handler "
"has gone out of scope\n");
/* Produce a core dump, which we can examine with GDB to look at the
frames on the stack, if desired */
printf("===\n");
printf("About to abort\n");
abort();
}
static void
recur(int lev, int *xp)
{
int rloc;
int big[65536-12]; /* 12*4 == 48 other bytes allocated on
this stack frame */
tos = (char *) &rloc;
big[0] = lev;
big[0]++;
printf("&rloc = %p (%d) (%d)\n", (void *) &rloc, lev, *xp);
if (lev > 1)
recur(lev - 1, xp);
else {
printf("exit() from recur()\n");
exit(EXIT_SUCCESS);
}
}
int
main(int argc, char *argv[])
{
int lev;
int *xp;
int xx;
if (argc < 2) {
fprintf(stderr, "Usage: %s {s|h} [how]\n", argv[0]);
fprintf(stderr, "\ts => exitFunc() arg is in main() stack\n");
fprintf(stderr, "\th => exitFunc() arg is allocated on heapn");
fprintf(stderr, "\tIf 'how' is not present, then return from main()\n");
fprintf(stderr, "\tIf 'how' is 0, then exit() from main()\n");
fprintf(stderr, "\tIf 'how' is > 0, then make 'how' recursive "
"function calls, and then exit()\n");
exit(EXIT_FAILURE);
}
tos = (char *) &xp;
if (argv[1][0] == 'h') {
xp = malloc(sizeof(int));
if (xp == NULL) {
perror("malloc");
exit(EXIT_FAILURE);
}
printf("Argument for exitFunc() is allocated on heap\n");
} else {
xp = &xx;
printf("Argument for exitFunc() is allocated on stack in main()\n");
}
Mark Wielaard [Wed, 29 May 2019 23:08:39 +0000 (01:08 +0200)]
mprotect.2: pkey_mprotect() acts like mprotect() if pkey is set to -1, not 0
The mprotect.2 NOTES say:
On systems that do not support protection keys in
hardware, pkey_mprotect() may still be used, but pkey must
be set to 0. When called this way, the operation of
pkey_mprotect() is equivalent to mprotect().
But this is not what the glibc manual says:
It is also possible to call pkey_mprotect with a key value
of -1, in which case it will behave in the same way as
mprotect.
Which is correct. Both the glibc implementation and the
kernel check whether pkey is -1. 0 is not a valid pkey when
memory protection keys are not supported in hardware.
Signed-off-by: Mark Wielaard <mark@klomp.org> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
I've found the exec man page quite difficult to read when trying
to find the behavior for a specific function. Since the names of
the functions are inline and the order of the descriptions isn't
clear, it's hard to find which paragraphs apply to each function.
I thought it would be much easier to read if the grouping based on
letters is stated.
fanotify.7: Reword FAN_REPORT_FID data structure inclusion semantics
Improved the readability of a sentence that describes the use of
FAN_REPORT_FID and how this particular flag influences what data
structures a listening application could expect to receive when
describing an event.
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
fanotify.7, fanotify_init.2, fanotify_mark.2: Document FAN_REPORT_FID and directory modification events
Details relating to the new initialization flag FAN_REPORT_FID has been
added. As part of the FAN_REPORT_FID feature, a new set of event masks are
available and have been documented accordingly.
A simple example program has been added to also support the understanding
and use of FAN_REPORT_FID and directory modification events.
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Wed, 22 May 2019 19:38:36 +0000 (21:38 +0200)]
ld.so.8: Note some further details of secure-execution mode
Note some further details of the treatment of environment
variables in secure execution mode. In particular (as noted by
Matthias Hertel), note that ignored environment variables are also
stripped from the environment. Furthermore, there are some other
variables, not used by the dynamic linker itself, that are also
treated in this way (see the glibc source file
sysdeps/generic/unsecvars.h).
Reported-by: Matthias Hertel <Matthias.Hertel@rohde-schwarz.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The BUGS section already explains why you need to be cautious
about using mallinfo, but given the number of bug reports we see
on Android, it seems not many people are reading that far. Call it
out up front.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Sun, 14 Apr 2019 17:34:35 +0000 (19:34 +0200)]
clone.2: CLONE_CHILD_SETTID has effect before clone() returns *in the child*
CLONE_CHILD_SETTID may not have had effect by the time clone()
returns in the parent, which could bre relevant if the
CLONE_VM flag is employed. The relevant kernel code is in
schedule_tail(), which is called in ret_from_fork()
in the child.
See https://bugzilla.kernel.org/show_bug.cgi?id=203105
Demonstration using the program shown below (inspired by a simpler
example from Jakub):
Carlos O'Donell [Thu, 28 Mar 2019 18:01:28 +0000 (14:01 -0400)]
malloc_trim.3: Update trimming information
Since glibc 2.8, commit 68631c8eb92, the malloc_trim function has
iterated over all arenas and free'd back to the OS all page runs
that were free. This allows an application to call malloc_trim to
consolidate fragmented chunks and free back any pages it can to
potentially reduce RSS usage.
This correctness of the man page was recently brought to light by
an article [1] where Ruby developers discovered that malloc_trim
did not behave as the man page indicated.
This change makes it clear that the intent of malloc_trim is to
trim all space that is no longer needed, and any restrictions are
implementation details. In the notes we highlight the change in
behaviour for post glibc 2.8 and pre glibc 2.8.
Where is the initial read position for an "a+" stream?
POSIX leaves this unspecified. Most BSD man pages are silent, and MacOS
has the ambiguous "The stream is positioned at the end of the file", not
differentiating between reads and writes other than to say that fseek(3)
does not affect writes. glibc's documentation explicitly specifies that
the initial read position is the beginning of the file.
My new wording is based on the BSD implementations, so you may prefer
to replace the non-glibc section with "unspecified", or indeed remove
all claims about the initial read position.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Fri, 12 Apr 2019 09:11:03 +0000 (11:11 +0200)]
stdarg.3: Add a note that ... in function signature means a variadic function
Egmont suggested adding this, because the string "..." appears
at several other points in the page, but just to indicate that
some text is omitted from example code.
Reported-by: Egmont Koblinger <egmont@gmail.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
projects / thirdparty / man-pages.git / log
