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Subject[RFC 1/8] param: allow parse_args to work non-destructively.

There are currently several places where we make a temporary command line
to mangle: it's fairly simple for parse_args() to demangle in place.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
include/linux/moduleparam.h | 3 +-
init/main.c | 6 ++---
kernel/module.c | 2 -
kernel/params.c | 46 +++++++++++++++++++++++++++++++++++++-------
4 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -136,7 +136,8 @@ extern int parse_args(const char *name,
char *args,
struct kernel_param *params,
unsigned num,
- int (*unknown)(char *param, char *val));
+ int (*unknown)(char *param, char *val),
+ bool restore_args);

/* All the helper functions */
/* The macros to do compile-time type checking stolen from Jakub
diff --git a/init/main.c b/init/main.c
--- a/init/main.c
+++ b/init/main.c
@@ -509,7 +509,7 @@ void __init parse_early_param(void)

/* All fall through to do_early_param. */
strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
- parse_args("early options", tmp_cmdline, NULL, 0, do_early_param);
+ parse_args("early options", tmp_cmdline, NULL, 0, do_early_param, true);
done = 1;
}

@@ -589,7 +589,7 @@ asmlinkage void __init start_kernel(void
parse_early_param();
parse_args("Booting kernel", static_command_line, __start___param,
__stop___param - __start___param,
- &unknown_bootoption);
+ &unknown_bootoption, false);
if (!irqs_disabled()) {
printk(KERN_WARNING "start_kernel(): bug: interrupts were "
"enabled *very* early, fixing it\n");
diff --git a/kernel/module.c b/kernel/module.c
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2239,7 +2239,7 @@ static noinline struct module *load_modu
*/
list_add_rcu(&mod->list, &modules);

- err = parse_args(mod->name, mod->args, kp, num_kp, NULL);
+ err = parse_args(mod->name, mod->args, kp, num_kp, NULL, false);
if (err < 0)
goto unlink;

diff --git a/kernel/params.c b/kernel/params.c
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -72,9 +72,36 @@ static int parse_one(char *param,
return -ENOENT;
}

+struct replacements {
+ unsigned int num;
+ struct {
+ char *pos;
+ char oldc;
+ } replace[3];
+};
+
+static void replace(char *place, char newc, struct replacements *replacements)
+{
+ BUG_ON(replacements->num == ARRAY_SIZE(replacements->replace));
+ replacements->replace[replacements->num].pos = place;
+ replacements->replace[replacements->num].oldc = *place;
+ *place = newc;
+ replacements->num++;
+
+}
+
+static void unreplace_all(struct replacements *replaced)
+{
+ unsigned int i;
+
+ for (i = 0; i < replaced->num; i++)
+ *replaced->replace[i].pos = replaced->replace[i].oldc;
+}
+
/* You can use " around spaces, but can't escape ". */
/* Hyphens and underscores equivalent in parameter names. */
-static char *next_arg(char *args, char **param, char **val)
+static char *next_arg(char *args, char **param, char **val,
+ struct replacements *replacements)
{
unsigned int i, equals = 0;
int in_quote = 0, quoted = 0;
@@ -101,21 +128,21 @@ static char *next_arg(char *args, char *
if (!equals)
*val = NULL;
else {
- args[equals] = '\0';
+ replace(&args[equals], '\0', replacements);
*val = args + equals + 1;

/* Don't include quotes in value. */
if (**val == '"') {
(*val)++;
if (args[i-1] == '"')
- args[i-1] = '\0';
+ replace(&args[i-1], '\0', replacements);
}
if (quoted && args[i-1] == '"')
- args[i-1] = '\0';
+ replace(&args[i-1], '\0', replacements);
}

if (args[i]) {
- args[i] = '\0';
+ replace(&args[i], '\0', replacements);
next = args + i + 1;
} else
next = args + i;
@@ -131,7 +158,8 @@ int parse_args(const char *name,
char *args,
struct kernel_param *params,
unsigned num,
- int (*unknown)(char *param, char *val))
+ int (*unknown)(char *param, char *val),
+ bool restore_args)
{
char *param, *val;

@@ -144,14 +172,18 @@ int parse_args(const char *name,
while (*args) {
int ret;
int irq_was_disabled;
+ struct replacements replaced = { .num = 0 };

- args = next_arg(args, &param, &val);
+ args = next_arg(args, &param, &val, &replaced);
irq_was_disabled = irqs_disabled();
ret = parse_one(param, val, params, num, unknown);
if (irq_was_disabled && !irqs_disabled()) {
printk(KERN_WARNING "parse_args(): option '%s' enabled "
"irq's!\n", param);
}
+ if (restore_args)
+ unreplace_all(&replaced);
+
switch (ret) {
case -ENOENT:
printk(KERN_ERR "%s: Unknown parameter `%s'\n",



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