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abcdc1c694
cmdline_find_option_bool() keeps track of position in two strings:
1. the command-line
2. the option we are searchign for in the command-line
We plow through each character in the command-line one at a time, always
moving forward. We move forward in the option ('opptr') when we match
characters in 'cmdline'. We reset the 'opptr' only when we go in to the
'st_wordstart' state.
But, if we fail to match an option because we see a space
(state=st_wordcmp, *opptr='\0',c=' '), we set state='st_wordskip' and
'break', moving to the next character. But, that move to the next
character is the one *after* the ' '. This means that we will miss a
'st_wordstart' state.
For instance, if we have
cmdline = "foo fool";
and are searching for "fool", we have:
"fool"
opptr = ----^
"foo fool"
c = --------^
We see that 'l' != ' ', set state=st_wordskip, break, and then move 'c', so:
"foo fool"
c = ---------^
and are still in state=st_wordskip. We will stay in wordskip until we
have skipped "fool", thus missing the option we were looking for. This
*only* happens when you have a partially- matching word followed by a
matching one.
To fix this, we always fall *into* the 'st_wordskip' state when we set
it.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151222225239.8E1DCA58@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
107 lines
2.3 KiB
C
107 lines
2.3 KiB
C
/*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* Misc librarized functions for cmdline poking.
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*/
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/ctype.h>
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#include <asm/setup.h>
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static inline int myisspace(u8 c)
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{
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return c <= ' '; /* Close enough approximation */
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}
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/**
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* Find a boolean option (like quiet,noapic,nosmp....)
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*
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* @cmdline: the cmdline string
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* @option: option string to look for
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*
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* Returns the position of that @option (starts counting with 1)
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* or 0 on not found. @option will only be found if it is found
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* as an entire word in @cmdline. For instance, if @option="car"
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* then a cmdline which contains "cart" will not match.
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*/
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int cmdline_find_option_bool(const char *cmdline, const char *option)
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{
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char c;
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int pos = 0, wstart = 0;
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const char *opptr = NULL;
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enum {
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st_wordstart = 0, /* Start of word/after whitespace */
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st_wordcmp, /* Comparing this word */
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st_wordskip, /* Miscompare, skip */
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} state = st_wordstart;
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if (!cmdline)
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return -1; /* No command line */
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if (!strlen(cmdline))
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return 0;
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/*
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* This 'pos' check ensures we do not overrun
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* a non-NULL-terminated 'cmdline'
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*/
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while (pos < COMMAND_LINE_SIZE) {
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c = *(char *)cmdline++;
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pos++;
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switch (state) {
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case st_wordstart:
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if (!c)
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return 0;
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else if (myisspace(c))
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break;
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state = st_wordcmp;
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opptr = option;
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wstart = pos;
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/* fall through */
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case st_wordcmp:
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if (!*opptr) {
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/*
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* We matched all the way to the end of the
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* option we were looking for. If the
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* command-line has a space _or_ ends, then
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* we matched!
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*/
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if (!c || myisspace(c))
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return wstart;
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/*
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* We hit the end of the option, but _not_
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* the end of a word on the cmdline. Not
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* a match.
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*/
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} else if (!c) {
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/*
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* Hit the NULL terminator on the end of
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* cmdline.
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*/
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return 0;
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} else if (c == *opptr++) {
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/*
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* We are currently matching, so continue
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* to the next character on the cmdline.
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*/
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break;
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}
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state = st_wordskip;
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/* fall through */
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case st_wordskip:
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if (!c)
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return 0;
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else if (myisspace(c))
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state = st_wordstart;
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break;
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}
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}
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return 0; /* Buffer overrun */
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}
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