From d5a572a4cb1e484d8d8c79bdfd16aaa18fa1470b Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Mon, 11 Mar 2019 23:28:51 -0700 Subject: [PATCH] proc: calculate end pointer for /proc/*/* lookup at compile time Compilers like to transform loops like for (i = 0; i < n; i++) { [use p[i]] } into for (p = p0; p < end; p++) { ... } Do it by hand, so that it results in overall simpler loop and smaller code. Space savings: $ ./scripts/bloat-o-meter ../vmlinux-001 ../obj/vmlinux add/remove: 0/0 grow/shrink: 2/1 up/down: 4/-9 (-5) Function old new delta proc_tid_base_lookup 17 19 +2 proc_tgid_base_lookup 17 19 +2 proc_pident_lookup 179 170 -9 The same could be done to proc_pident_readdir(), but the code becomes bigger for some reason. [sfr@canb.auug.org.au: merge fix for proc_pident_lookup() API change] Link: http://lkml.kernel.org/r/20190131160135.4a8ae70b@canb.auug.org.au Link: http://lkml.kernel.org/r/20190114200422.GB9680@avx2 Signed-off-by: Alexey Dobriyan Signed-off-by: Stephen Rothwell Cc: James Morris Cc: Alexey Dobriyan Cc: Casey Schaufler Cc: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 5ab1849971b4..1b548d060d28 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2459,11 +2459,10 @@ static struct dentry *proc_pident_instantiate(struct dentry *dentry, static struct dentry *proc_pident_lookup(struct inode *dir, struct dentry *dentry, - const struct pid_entry *ents, - unsigned int nents) + const struct pid_entry *p, + const struct pid_entry *end) { struct task_struct *task = get_proc_task(dir); - const struct pid_entry *p, *last; struct dentry *res = ERR_PTR(-ENOENT); if (!task) @@ -2473,8 +2472,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir, * Yes, it does not scale. And it should not. Don't add * new entries into /proc// without very good reasons. */ - last = &ents[nents]; - for (p = ents; p < last; p++) { + for (; p < end; p++) { if (p->len != dentry->d_name.len) continue; if (!memcmp(dentry->d_name.name, p->name, p->len)) { @@ -2610,7 +2608,7 @@ static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \ { \ return proc_pident_lookup(dir, dentry, \ LSM##_attr_dir_stuff, \ - ARRAY_SIZE(LSM##_attr_dir_stuff)); \ + LSM##_attr_dir_stuff + ARRAY_SIZE(LSM##_attr_dir_stuff)); \ } \ \ static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \ @@ -2655,7 +2653,8 @@ static struct dentry *proc_attr_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { return proc_pident_lookup(dir, dentry, - attr_dir_stuff, ARRAY_SIZE(attr_dir_stuff)); + attr_dir_stuff, + attr_dir_stuff + ARRAY_SIZE(attr_dir_stuff)); } static const struct inode_operations proc_attr_dir_inode_operations = { @@ -3091,7 +3090,8 @@ static const struct file_operations proc_tgid_base_operations = { static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { return proc_pident_lookup(dir, dentry, - tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff)); + tgid_base_stuff, + tgid_base_stuff + ARRAY_SIZE(tgid_base_stuff)); } static const struct inode_operations proc_tgid_base_inode_operations = { @@ -3463,7 +3463,8 @@ static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx) static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { return proc_pident_lookup(dir, dentry, - tid_base_stuff, ARRAY_SIZE(tid_base_stuff)); + tid_base_stuff, + tid_base_stuff + ARRAY_SIZE(tid_base_stuff)); } static const struct file_operations proc_tid_base_operations = { -- 2.30.2