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kobject_uevent: Allocate environment buffer on the stack

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The environment buffer isn't very big; when it's allocated on the stack,
kobject_uevent_env's stack frame size increases to just over 2 KiB,
which is safe considering that we have a 16 KiB stack.

Allocate the environment buffer on the stack instead of using the slab
allocator in order to improve performance.

Change-Id: I175eda1be09007436f77dd6f185931e6a1d9facb
Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Yaroslav Furman <yaro330@gmail.com>
Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>
This commit is contained in:
Sultan Alsawaf 2019-07-12 17:26:31 -07:00 committed by Richard Raya
parent bcaa3ffd5d
commit 15c8a438c6
2 changed files with 22 additions and 27 deletions
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1
lib/Makefile
View File

@ -46,6 +46,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
earlycpio.o seq_buf.o siphash.o \
nodemask.o win_minmax.o
CFLAGS_kobject_uevent.o += -Wframe-larger-than=3072
lib-$(!CONFIG_ARM64) += nmi_backtrace.o
lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o

48
lib/kobject_uevent.c
View File

@ -328,7 +328,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env)
int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
char *envp_ext[])
{
struct kobj_uevent_env *env;
struct kobj_uevent_env env;
const char *action_string = kobject_actions[action];
const char *devpath = NULL;
const char *subsystem;
@ -394,11 +394,6 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
return 0;
}
/* environment buffer */
env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
if (!env)
return -ENOMEM;
/* complete object path */
devpath = kobject_get_path(kobj, GFP_KERNEL);
if (!devpath) {
@ -406,21 +401,23 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
goto exit;
}
memset(&env, 0, sizeof(env));
/* default keys */
retval = add_uevent_var(env, "ACTION=%s", action_string);
retval = add_uevent_var(&env, "ACTION=%s", action_string);
if (retval)
goto exit;
retval = add_uevent_var(env, "DEVPATH=%s", devpath);
retval = add_uevent_var(&env, "DEVPATH=%s", devpath);
if (retval)
goto exit;
retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
retval = add_uevent_var(&env, "SUBSYSTEM=%s", subsystem);
if (retval)
goto exit;
/* keys passed in from the caller */
if (envp_ext) {
for (i = 0; envp_ext[i]; i++) {
retval = add_uevent_var(env, "%s", envp_ext[i]);
retval = add_uevent_var(&env, "%s", envp_ext[i]);
if (retval)
goto exit;
}
@ -428,7 +425,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
/* let the kset specific function add its stuff */
if (uevent_ops && uevent_ops->uevent) {
retval = uevent_ops->uevent(kset, kobj, env);
retval = uevent_ops->uevent(kset, kobj, &env);
if (retval) {
pr_debug("kobject: '%s' (%p): %s: uevent() returned "
"%d\n", kobject_name(kobj), kobj,
@ -450,7 +447,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
break;
case KOBJ_UNBIND:
zap_modalias_env(env);
zap_modalias_env(&env);
break;
default:
@ -459,7 +456,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
mutex_lock(&uevent_sock_mutex);
/* we will send an event, so request a new sequence number */
retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
retval = add_uevent_var(&env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
if (retval) {
mutex_unlock(&uevent_sock_mutex);
goto exit;
@ -477,7 +474,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
/* allocate message with the maximum possible size */
len = strlen(action_string) + strlen(devpath) + 2;
skb = alloc_skb(len + env->buflen, GFP_KERNEL);
skb = alloc_skb(len + env.buflen, GFP_KERNEL);
if (skb) {
char *scratch;
@ -486,10 +483,10 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
sprintf(scratch, "%s@%s", action_string, devpath);
/* copy keys to our continuous event payload buffer */
for (i = 0; i < env->envp_idx; i++) {
len = strlen(env->envp[i]) + 1;
for (i = 0; i < env.envp_idx; i++) {
len = strlen(env.envp[i]) + 1;
scratch = skb_put(skb, len);
strcpy(scratch, env->envp[i]);
strcpy(scratch, env.envp[i]);
}
NETLINK_CB(skb).dst_group = 1;
@ -511,31 +508,28 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
struct subprocess_info *info;
retval = add_uevent_var(env, "HOME=/");
retval = add_uevent_var(&env, "HOME=/");
if (retval)
goto exit;
retval = add_uevent_var(env,
retval = add_uevent_var(&env,
"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
if (retval)
goto exit;
retval = init_uevent_argv(env, subsystem);
retval = init_uevent_argv(&env, subsystem);
if (retval)
goto exit;
retval = -ENOMEM;
info = call_usermodehelper_setup(env->argv[0], env->argv,
env->envp, GFP_KERNEL,
NULL, cleanup_uevent_env, env);
if (info) {
info = call_usermodehelper_setup(env.argv[0], env.argv,
env.envp, GFP_KERNEL,
NULL, cleanup_uevent_env, &env);
if (info)
retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
env = NULL; /* freed by cleanup_uevent_env */
}
}
#endif
exit:
kfree(devpath);
kfree(env);
return retval;
}
EXPORT_SYMBOL_GPL(kobject_uevent_env);