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![Neel Natu](/assets/img/avatar_default.png)
An argument list like "arg=val arg2 \"" can trigger a page fault if the page pointed by 'args[0xffffffff]' is not mapped and potential memory corruption otherwise (unlikely but possible if the bogus address is mapped and contents happen to match the ascii value of the quote character). The fix is to ensure that we load 'args[i-1]' only when (i > 0). Prior to this commit the following command would trigger an unhandled page fault in the kernel: root@(none):/linus/fs/fat# insmod ./fat.ko "foo=bar \"" [ 33.870507] BUG: unable to handle page fault for address: ffff888204252608 [ 33.872180] #PF: supervisor read access in kernel mode [ 33.873414] #PF: error_code(0x0000) - not-present page [ 33.874650] PGD 4401067 P4D 4401067 PUD 0 [ 33.875321] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC PTI [ 33.876113] CPU: 16 PID: 399 Comm: insmod Not tainted 5.19.0-dbg-DEV #4 [ 33.877193] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014 [ 33.878739] RIP: 0010:next_arg+0xd1/0x110 [ 33.879399] Code: 22 75 1d 41 c6 04 01 00 41 80 f8 22 74 18 eb 35 4c 89 0e 45 31 d2 4c 89 cf 48 c7 02 00 00 00 00 41 80 f8 22 75 1f 41 8d 42 ff <41> 80 3c 01 22 75 14 41 c6 04 01 00 eb 0d 48 c7 02 00 00 00 00 41 [ 33.882338] RSP: 0018:ffffc90001253d08 EFLAGS: 00010246 [ 33.883174] RAX: 00000000ffffffff RBX: ffff888104252608 RCX: 0fc317bba1c1dd00 [ 33.884311] RDX: ffffc90001253d40 RSI: ffffc90001253d48 RDI: ffff888104252609 [ 33.885450] RBP: ffffc90001253d10 R08: 0000000000000022 R09: ffff888104252609 [ 33.886595] R10: 0000000000000000 R11: ffffffff82c7ff20 R12: 0000000000000282 [ 33.887748] R13: 00000000ffff8000 R14: 0000000000000000 R15: 0000000000007fff [ 33.888887] FS: 00007f04ec7432c0(0000) GS:ffff88813d300000(0000) knlGS:0000000000000000 [ 33.890183] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 33.891111] CR2: ffff888204252608 CR3: 0000000100f36005 CR4: 0000000000170ee0 [ 33.892241] Call Trace: [ 33.892641] <TASK> [ 33.892989] parse_args+0x8f/0x220 [ 33.893538] load_module+0x138b/0x15a0 [ 33.894149] ? prepare_coming_module+0x50/0x50 [ 33.894879] ? kernel_read_file_from_fd+0x5f/0x90 [ 33.895639] __se_sys_finit_module+0xce/0x130 [ 33.896342] __x64_sys_finit_module+0x1d/0x20 [ 33.897042] do_syscall_64+0x44/0xa0 [ 33.897622] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 33.898434] RIP: 0033:0x7f04ec85ef79 [ 33.899009] Code: 48 8d 3d da db 0d 00 0f 05 eb a5 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c7 9e 0d 00 f7 d8 64 89 01 48 [ 33.901912] RSP: 002b:00007fffae81bfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 [ 33.903081] RAX: ffffffffffffffda RBX: 0000559c5f1d2640 RCX: 00007f04ec85ef79 [ 33.904191] RDX: 0000000000000000 RSI: 0000559c5f1d12a0 RDI: 0000000000000003 [ 33.905304] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 33.906421] R10: 0000000000000003 R11: 0000000000000246 R12: 0000559c5f1d12a0 [ 33.907526] R13: 0000000000000000 R14: 0000559c5f1d25f0 R15: 0000559c5f1d12a0 [ 33.908631] </TASK> [ 33.908986] Modules linked in: fat(+) [last unloaded: fat] [ 33.909843] CR2: ffff888204252608 [ 33.910375] ---[ end trace 0000000000000000 ]--- [ 33.911172] RIP: 0010:next_arg+0xd1/0x110 [ 33.911796] Code: 22 75 1d 41 c6 04 01 00 41 80 f8 22 74 18 eb 35 4c 89 0e 45 31 d2 4c 89 cf 48 c7 02 00 00 00 00 41 80 f8 22 75 1f 41 8d 42 ff <41> 80 3c 01 22 75 14 41 c6 04 01 00 eb 0d 48 c7 02 00 00 00 00 41 [ 33.914643] RSP: 0018:ffffc90001253d08 EFLAGS: 00010246 [ 33.915446] RAX: 00000000ffffffff RBX: ffff888104252608 RCX: 0fc317bba1c1dd00 [ 33.916544] RDX: ffffc90001253d40 RSI: ffffc90001253d48 RDI: ffff888104252609 [ 33.917636] RBP: ffffc90001253d10 R08: 0000000000000022 R09: ffff888104252609 [ 33.918727] R10: 0000000000000000 R11: ffffffff82c7ff20 R12: 0000000000000282 [ 33.919821] R13: 00000000ffff8000 R14: 0000000000000000 R15: 0000000000007fff [ 33.920908] FS: 00007f04ec7432c0(0000) GS:ffff88813d300000(0000) knlGS:0000000000000000 [ 33.922125] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 33.923017] CR2: ffff888204252608 CR3: 0000000100f36005 CR4: 0000000000170ee0 [ 33.924098] Kernel panic - not syncing: Fatal exception [ 33.925776] Kernel Offset: disabled [ 33.926347] Rebooting in 10 seconds.. Link: https://lkml.kernel.org/r/20220728232434.1666488-1-neelnatu@google.com Signed-off-by: Neel Natu <neelnatu@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
275 lines
5.8 KiB
C
275 lines
5.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* linux/lib/cmdline.c
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* Helper functions generally used for parsing kernel command line
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* and module options.
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*
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* Code and copyrights come from init/main.c and arch/i386/kernel/setup.c.
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*
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* GNU Indent formatting options for this file: -kr -i8 -npsl -pcs
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*/
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#include <linux/export.h>
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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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/*
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* If a hyphen was found in get_option, this will handle the
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* range of numbers, M-N. This will expand the range and insert
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* the values[M, M+1, ..., N] into the ints array in get_options.
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*/
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static int get_range(char **str, int *pint, int n)
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{
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int x, inc_counter, upper_range;
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(*str)++;
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upper_range = simple_strtol((*str), NULL, 0);
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inc_counter = upper_range - *pint;
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for (x = *pint; n && x < upper_range; x++, n--)
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*pint++ = x;
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return inc_counter;
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}
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/**
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* get_option - Parse integer from an option string
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* @str: option string
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* @pint: (optional output) integer value parsed from @str
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*
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* Read an int from an option string; if available accept a subsequent
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* comma as well.
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*
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* When @pint is NULL the function can be used as a validator of
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* the current option in the string.
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*
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* Return values:
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* 0 - no int in string
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* 1 - int found, no subsequent comma
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* 2 - int found including a subsequent comma
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* 3 - hyphen found to denote a range
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*
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* Leading hyphen without integer is no integer case, but we consume it
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* for the sake of simplification.
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*/
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int get_option(char **str, int *pint)
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{
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char *cur = *str;
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int value;
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if (!cur || !(*cur))
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return 0;
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if (*cur == '-')
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value = -simple_strtoull(++cur, str, 0);
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else
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value = simple_strtoull(cur, str, 0);
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if (pint)
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*pint = value;
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if (cur == *str)
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return 0;
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if (**str == ',') {
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(*str)++;
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return 2;
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}
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if (**str == '-')
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return 3;
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return 1;
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}
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EXPORT_SYMBOL(get_option);
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/**
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* get_options - Parse a string into a list of integers
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* @str: String to be parsed
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* @nints: size of integer array
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* @ints: integer array (must have room for at least one element)
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*
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* This function parses a string containing a comma-separated
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* list of integers, a hyphen-separated range of _positive_ integers,
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* or a combination of both. The parse halts when the array is
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* full, or when no more numbers can be retrieved from the
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* string.
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*
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* When @nints is 0, the function just validates the given @str and
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* returns the amount of parseable integers as described below.
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*
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* Returns:
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*
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* The first element is filled by the number of collected integers
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* in the range. The rest is what was parsed from the @str.
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*
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* Return value is the character in the string which caused
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* the parse to end (typically a null terminator, if @str is
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* completely parseable).
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*/
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char *get_options(const char *str, int nints, int *ints)
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{
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bool validate = (nints == 0);
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int res, i = 1;
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while (i < nints || validate) {
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int *pint = validate ? ints : ints + i;
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res = get_option((char **)&str, pint);
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if (res == 0)
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break;
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if (res == 3) {
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int n = validate ? 0 : nints - i;
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int range_nums;
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range_nums = get_range((char **)&str, pint, n);
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if (range_nums < 0)
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break;
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/*
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* Decrement the result by one to leave out the
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* last number in the range. The next iteration
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* will handle the upper number in the range
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*/
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i += (range_nums - 1);
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}
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i++;
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if (res == 1)
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break;
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}
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ints[0] = i - 1;
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return (char *)str;
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}
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EXPORT_SYMBOL(get_options);
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/**
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* memparse - parse a string with mem suffixes into a number
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* @ptr: Where parse begins
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* @retptr: (output) Optional pointer to next char after parse completes
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*
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* Parses a string into a number. The number stored at @ptr is
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* potentially suffixed with K, M, G, T, P, E.
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*/
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unsigned long long memparse(const char *ptr, char **retptr)
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{
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char *endptr; /* local pointer to end of parsed string */
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unsigned long long ret = simple_strtoull(ptr, &endptr, 0);
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switch (*endptr) {
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case 'E':
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case 'e':
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ret <<= 10;
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fallthrough;
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case 'P':
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case 'p':
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ret <<= 10;
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fallthrough;
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case 'T':
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case 't':
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ret <<= 10;
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fallthrough;
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case 'G':
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case 'g':
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ret <<= 10;
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fallthrough;
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case 'M':
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case 'm':
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ret <<= 10;
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fallthrough;
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case 'K':
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case 'k':
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ret <<= 10;
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endptr++;
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fallthrough;
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default:
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break;
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}
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if (retptr)
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*retptr = endptr;
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return ret;
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}
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EXPORT_SYMBOL(memparse);
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/**
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* parse_option_str - Parse a string and check an option is set or not
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* @str: String to be parsed
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* @option: option name
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*
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* This function parses a string containing a comma-separated list of
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* strings like a=b,c.
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*
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* Return true if there's such option in the string, or return false.
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*/
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bool parse_option_str(const char *str, const char *option)
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{
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while (*str) {
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if (!strncmp(str, option, strlen(option))) {
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str += strlen(option);
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if (!*str || *str == ',')
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return true;
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}
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while (*str && *str != ',')
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str++;
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if (*str == ',')
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str++;
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}
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return false;
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}
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/*
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* Parse a string to get a param value pair.
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* You can use " around spaces, but can't escape ".
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* Hyphens and underscores equivalent in parameter names.
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*/
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char *next_arg(char *args, char **param, char **val)
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{
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unsigned int i, equals = 0;
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int in_quote = 0, quoted = 0;
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if (*args == '"') {
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args++;
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in_quote = 1;
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quoted = 1;
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}
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for (i = 0; args[i]; i++) {
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if (isspace(args[i]) && !in_quote)
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break;
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if (equals == 0) {
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if (args[i] == '=')
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equals = i;
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}
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if (args[i] == '"')
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in_quote = !in_quote;
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}
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*param = args;
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if (!equals)
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*val = NULL;
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else {
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args[equals] = '\0';
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*val = args + equals + 1;
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/* Don't include quotes in value. */
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if (**val == '"') {
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(*val)++;
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if (args[i-1] == '"')
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args[i-1] = '\0';
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}
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}
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if (quoted && i > 0 && args[i-1] == '"')
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args[i-1] = '\0';
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if (args[i]) {
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args[i] = '\0';
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args += i + 1;
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} else
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args += i;
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/* Chew up trailing spaces. */
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return skip_spaces(args);
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}
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EXPORT_SYMBOL(next_arg);
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