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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2016-01-15 16:58:37 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 11:17:26 -0800
commitd048419311ff16ba420f4b1bdf93a3d74057b53a (patch)
treef7c7ca69b73f37b7227f1723ad48a1ae71068b01 /lib/vsprintf.c
parent34fc8b9076254513e00607134792a1b67483d2cf (diff)
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lib/vsprintf.c: expand field_width to 24 bits
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 [akpm@linux-foundation.org: avoid open-coded BUILD_BUG_ON] Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reported-by: Maurizio Lombardi <mlombard@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Joe Perches <joe@perches.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/vsprintf.c')
-rw-r--r--lib/vsprintf.c42
1 files changed, 22 insertions, 20 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c537a73a62e8..c09182e07b05 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -383,13 +383,12 @@ 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;
static noinline_for_stack
char *number(char *buf, char *end, unsigned long long num,
@@ -403,6 +402,8 @@ char *number(char *buf, char *end, unsigned long long num,
int i;
bool is_zero = num == 0LL;
+ BUILD_BUG_ON(sizeof(struct printf_spec) != 8);
+
/* locase = 0 or 0x20. ORing digits or letters with 'locase'
* produces same digits or (maybe lowercased) letters */
locase = (spec.flags & SMALL);
@@ -1670,6 +1671,7 @@ 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) {
@@ -1752,16 +1754,16 @@ 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;
}
}
@@ -1818,19 +1820,19 @@ 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 {