From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Andrew Morton <akpm@linux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Kees Cook <keescook@chromium.org>,
Martin Kletzander <mkletzan@redhat.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
Joe Perches <joe@perches.com>,
Maurizio Lombardi <mlombard@redhat.com>,
Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH v3 04/14] lib/vsprintf.c: expand field_width to 24 bits
Date: Thu, 3 Dec 2015 21:51:03 +0100 [thread overview]
Message-ID: <1449175873-1780-5-git-send-email-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <1449175873-1780-1-git-send-email-linux@rasmusvillemoes.dk>
Maurizio Lombardi reported a problem [1] with the %pb extension: It
doesn't work for sufficiently large bitmaps, since the size is stashed
in the field_width field of the struct printf_spec, which is currently
an s16. Concretely, this manifested itself in
/sys/bus/pseudo/drivers/scsi_debug/map being empty, since the bitmap
printer got a size of 0, which is the 16 bit truncation of the actual
bitmap size.
We do want to keep struct printf_spec at 8 bytes so that it can
cheaply be passed by value. The qualifier field is only used for
internal bookkeeping in format_decode, so we might as well use a local
variable for that. This gives us an additional 8 bits, which we can
then use for the field width.
To stay in 8 bytes, we need to do a little rearranging and make the
type member a bitfield as well. For consistency, change all the
members to bit fields. gcc doesn't generate much worse code with these
changes (in fact, bloat-o-meter says we save 300 bytes - which I think
is a little surprising).
I didn't find a BUILD_BUG/compiletime_assertion/... which would work
outside function context, so for now I just open-coded it.
[1] http://thread.gmane.org/gmane.linux.kernel/2034835
Reported-by: Maurizio Lombardi <mlombard@redhat.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Joe Perches <joe@perches.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
lib/vsprintf.c | 41 +++++++++++++++++++++--------------------
1 file changed, 21 insertions(+), 20 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 63ca52366049..01c3aa638582 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -380,13 +380,13 @@ enum format_type {
};
struct printf_spec {
- u8 type; /* format_type enum */
- u8 flags; /* flags to number() */
- u8 base; /* number base, 8, 10 or 16 only */
- u8 qualifier; /* number qualifier, one of 'hHlLtzZ' */
- s16 field_width; /* width of output field */
- s16 precision; /* # of digits/chars */
-};
+ unsigned int type:8; /* format_type enum */
+ signed int field_width:24; /* width of output field */
+ unsigned int flags:8; /* flags to number() */
+ unsigned int base:8; /* number base, 8, 10 or 16 only */
+ signed int precision:16; /* # of digits/chars */
+} __packed;
+extern char __check_printf_spec[1-2*(sizeof(struct printf_spec) != 8)];
static noinline_for_stack
char *number(char *buf, char *end, unsigned long long num,
@@ -1641,6 +1641,7 @@ static noinline_for_stack
int format_decode(const char *fmt, struct printf_spec *spec)
{
const char *start = fmt;
+ char qualifier;
/* we finished early by reading the field width */
if (spec->type == FORMAT_TYPE_WIDTH) {
@@ -1723,16 +1724,16 @@ precision:
qualifier:
/* get the conversion qualifier */
- spec->qualifier = -1;
+ qualifier = 0;
if (*fmt == 'h' || _tolower(*fmt) == 'l' ||
_tolower(*fmt) == 'z' || *fmt == 't') {
- spec->qualifier = *fmt++;
- if (unlikely(spec->qualifier == *fmt)) {
- if (spec->qualifier == 'l') {
- spec->qualifier = 'L';
+ qualifier = *fmt++;
+ if (unlikely(qualifier == *fmt)) {
+ if (qualifier == 'l') {
+ qualifier = 'L';
++fmt;
- } else if (spec->qualifier == 'h') {
- spec->qualifier = 'H';
+ } else if (qualifier == 'h') {
+ qualifier = 'H';
++fmt;
}
}
@@ -1789,19 +1790,19 @@ qualifier:
return fmt - start;
}
- if (spec->qualifier == 'L')
+ if (qualifier == 'L')
spec->type = FORMAT_TYPE_LONG_LONG;
- else if (spec->qualifier == 'l') {
+ else if (qualifier == 'l') {
BUILD_BUG_ON(FORMAT_TYPE_ULONG + SIGN != FORMAT_TYPE_LONG);
spec->type = FORMAT_TYPE_ULONG + (spec->flags & SIGN);
- } else if (_tolower(spec->qualifier) == 'z') {
+ } else if (_tolower(qualifier) == 'z') {
spec->type = FORMAT_TYPE_SIZE_T;
- } else if (spec->qualifier == 't') {
+ } else if (qualifier == 't') {
spec->type = FORMAT_TYPE_PTRDIFF;
- } else if (spec->qualifier == 'H') {
+ } else if (qualifier == 'H') {
BUILD_BUG_ON(FORMAT_TYPE_UBYTE + SIGN != FORMAT_TYPE_BYTE);
spec->type = FORMAT_TYPE_UBYTE + (spec->flags & SIGN);
- } else if (spec->qualifier == 'h') {
+ } else if (qualifier == 'h') {
BUILD_BUG_ON(FORMAT_TYPE_USHORT + SIGN != FORMAT_TYPE_SHORT);
spec->type = FORMAT_TYPE_USHORT + (spec->flags & SIGN);
} else {
--
2.6.1
next prev parent reply other threads:[~2015-12-03 20:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-03 20:50 [PATCH v3 00/14] printf stuff for 4.5 Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 01/14] lib/vsprintf.c: pull out padding code from dentry_name() Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 02/14] lib/vsprintf.c: move string() below widen_string() Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 03/14] lib/vsprintf.c: eliminate potential race in string() Rasmus Villemoes
2015-12-03 20:51 ` Rasmus Villemoes [this message]
2015-12-03 20:54 ` [PATCH v3 04/14] lib/vsprintf.c: expand field_width to 24 bits Joe Perches
2015-12-03 21:28 ` Andy Shevchenko
2015-12-03 23:34 ` Andrew Morton
2015-12-04 0:03 ` Joe Perches
2015-12-04 8:59 ` Rasmus Villemoes
2015-12-04 9:02 ` Rasmus Villemoes
2015-12-03 23:41 ` Joe Perches
2015-12-03 20:51 ` [PATCH v3 05/14] lib/vsprintf.c: help gcc make number() smaller Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 06/14] lib/vsprintf.c: warn about too large precisions and field widths Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 07/14] lib/kasprintf.c: add sanity check to kvasprintf Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 08/14] lib/test_printf.c: don't BUG Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 09/14] lib/test_printf.c: check for out-of-bound writes Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 10/14] lib/test_printf.c: test precision quirks Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 11/14] lib/test_printf.c: add a few number() tests Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 12/14] lib/test_printf.c: account for kvasprintf tests Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 13/14] lib/test_printf.c: add test for large bitmaps Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 14/14] lib/test_printf.c: test dentry printing Rasmus Villemoes
2015-12-04 0:19 ` Andrew Morton
2015-12-04 8:16 ` Rasmus Villemoes
2015-12-04 8:46 ` Andrew Morton
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1449175873-1780-5-git-send-email-linux@rasmusvillemoes.dk \
--to=linux@rasmusvillemoes.dk \
--cc=akpm@linux-foundation.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=andy.shevchenko@gmail.com \
--cc=joe@perches.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mkletzan@redhat.com \
--cc=mlombard@redhat.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.