handle xlat_styles when decoding sa_mask

[Dmitry V. Levin]

On Fri, Feb 08, 2019 at 10:32:52PM +0300, Dmitry V. Levin wrote:
> Hi,
> 
> On Sat, Jan 05, 2019 at 12:10:38PM -0800, shankarapailoor wrote:
> > Hi,
> > 
> > Strace doesn't handle xlat styles properly when decoding the sa_mask
> > field of the sigaction struct,  Attached is a patch which decodes the
> > field as an array of bytes. Let me know what you think!
> > 
> > Regards,
> > Shankara Pailoor
> 
> > From 41d7cac5cf000f4e8b6ee675d231038cb786d2e1 Mon Sep 17 00:00:00 2001
> > From: Shankara Pailoor <shankarapailoor at gmail.com>
> > Date: Sat, 5 Jan 2019 11:49:28 -0800
> > Subject: [PATCH v1] properly handle xlat_styles when decoding sigaction mask
> > 
> > * signal.c (sprintsigmask_n): Decode sigaction mask as array of bytes under XLAT_RAW, VERBOSE.
> > * tests/printsamask.c: New file.
> > * tests/printsamask-Xabbrev.c: Likewise.
> > * tests/printsamask-Xraw.c: Likewise.
> > * tests/printsamask-Xverbose.c: Likewise.
> > * tests/pure_executables.list: Add printsamask-Xabbrev, printsamask-Xraw, printsamask-Xverbose.
> > * tests/gen_tests.in: Likewise.
> > ---
> >  signal.c                     | 32 +++++++++++++-
> >  tests/.gitignore             |  3 ++
> >  tests/gen_tests.in           |  3 ++
> >  tests/printsamask-Xabbrev.c  |  1 +
> >  tests/printsamask-Xraw.c     |  2 +
> >  tests/printsamask-Xverbose.c |  2 +
> >  tests/printsamask.c          | 81 ++++++++++++++++++++++++++++++++++++
> >  tests/pure_executables.list  |  3 ++
> >  8 files changed, 126 insertions(+), 1 deletion(-)
> >  create mode 100644 tests/printsamask-Xabbrev.c
> >  create mode 100644 tests/printsamask-Xraw.c
> >  create mode 100644 tests/printsamask-Xverbose.c
> >  create mode 100644 tests/printsamask.c
> > 
> > diff --git a/signal.c b/signal.c
> > index 418905f0..e3c5d8c3 100644
> > --- a/signal.c
> > +++ b/signal.c
> > @@ -166,8 +166,11 @@ sprintsigmask_n(const char *prefix, const void *sig_mask, unsigned int bytes)
> >  	 * Most of signal names have length 7,
> >  	 * average length of signal names is less than 7.
> >  	 * The length of prefix string does not exceed 16.
> > +	 * Under xlat_verbose we may have at most NSIG_BYTES in
> > +	 * the raw sa_mask array. We can safely allocate 8 bytes per entry
> >  	 */
> > -	static char outstr[128 + 8 * (NSIG_BYTES * 8 * 2 / 3)];
> > +	static char outstr[128 + 8 * (NSIG_BYTES * 8 * 2 / 3)
> > +				+ 8 * NSIG_BYTES];
> >  
> >  	char *s;
> >  	const uint32_t *mask;
> > @@ -178,6 +181,29 @@ sprintsigmask_n(const char *prefix, const void *sig_mask, unsigned int bytes)
> >  
> >  	s = stpcpy(outstr, prefix);
> >  
> > +	if (xlat_verbose(xlat_verbosity) != XLAT_STYLE_ABBREV) {
> > +		const char *mask = (char *) sig_mask;
> > +		const char *sep = "[";
> > +		unsigned int i, size;
> > +
> > +		size = (bytes >= NSIG_BYTES) ? NSIG_BYTES : bytes;
> > +		for (i = 0; i < size; i++) {
> > +			s = xappendstr(outstr, s, "%s0x%02x", sep, mask[i]);
> > +			sep = ", ";
> > +		}
> 
> I hope you understand that the output produced by your parser
> is different between big-endian and little-endian architectures.
> 
> [...]
> > +int
> > +main(void)
> > +{
> > +	unsigned int set_size = NSIG / 8;
> > +	void *const k_set = tail_alloc(set_size);
> > +	void *const old_set = tail_alloc(set_size);
> > +	TAIL_ALLOC_OBJECT_CONST_PTR(sigset_t, libc_set);
> > +
> > +	memset(k_set, 0, set_size);
> > +	sigemptyset(libc_set);
> > +	sigaddset(libc_set, SIGHUP);
> > +	memcpy(k_set, libc_set, set_size);
> > +
> > +	int rc = k_sigprocmask(SIG_SETMASK, k_set, old_set, set_size);
> > +#if XLAT_RAW
> > +	tprintf("rt_sigprocmask(0x2"
> > +		", [0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]"
> > +		", [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]"
> > +		", %u) = %s\n", set_size, sprintrc(rc));
> > +#elif XLAT_VERBOSE
> > +	tprintf("rt_sigprocmask(0x2 /* SIG_SETMASK */"
> > +		", [0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00] /* [HUP] */"
> > +		", [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00] /* [] */, %u) = %s\n",
> > +			set_size, sprintrc(rc));
> > +#else /* XLAT_ABBREV */
> > +	tprintf("rt_sigprocmask(SIG_SETMASK, [HUP], [], %u) = %s\n",
> > +			set_size, sprintrc(rc));
> > +#endif
> 
> Your test assumes that the output is produced on a big-endian

s/big-endian/little-endian/

> architecture, so it fails on big-endian architectures.


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