proc: fix PAGE_SIZE limit of /proc/$PID/cmdline
/proc/$PID/cmdline truncates output at PAGE_SIZE. It is easy to see with $ cat /proc/self/cmdline $(seq 1037) 2>/dev/null However, command line size was never limited to PAGE_SIZE but to 128 KB and relatively recently limitation was removed altogether. People noticed and ask questions: http://stackoverflow.com/questions/199130/how-do-i-increase-the-proc-pid-cmdline-4096-byte-limit seq file interface is not OK, because it kmalloc's for whole output and open + read(, 1) + sleep will pin arbitrary amounts of kernel memory. To not do that, limit must be imposed which is incompatible with arbitrary sized command lines. I apologize for hairy code, but this it direct consequence of command line layout in memory and hacks to support things like "init [3]". The loops are "unrolled" otherwise it is either macros which hide control flow or functions with 7-8 arguments with equal line count. There should be real setproctitle(2) or something. [akpm@linux-foundation.org: fix a billion min() warnings] Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Tested-by: Jarod Wilson <jarod@redhat.com> Acked-by: Jarod Wilson <jarod@redhat.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jan Stancek <jstancek@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>steinar/wifi_calib_4_9_kernel
Alexey Dobriyan
Linus Torvalds
parent
4a00e9df29
commit
c2c0bb4462
205
fs/proc/base.c
205
fs/proc/base.c
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@ -196,18 +196,205 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
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return result;
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}
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static int proc_pid_cmdline(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *task)
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static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
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size_t _count, loff_t *pos)
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{
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struct task_struct *tsk;
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struct mm_struct *mm;
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char *page;
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unsigned long count = _count;
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unsigned long arg_start, arg_end, env_start, env_end;
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unsigned long len1, len2, len;
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unsigned long p;
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char c;
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ssize_t rv;
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BUG_ON(*pos < 0);
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tsk = get_proc_task(file_inode(file));
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if (!tsk)
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return -ESRCH;
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mm = get_task_mm(tsk);
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put_task_struct(tsk);
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if (!mm)
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return 0;
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/* Check if process spawned far enough to have cmdline. */
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if (!mm->env_end) {
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rv = 0;
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goto out_mmput;
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}
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page = (char *)__get_free_page(GFP_TEMPORARY);
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if (!page) {
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rv = -ENOMEM;
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goto out_mmput;
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}
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down_read(&mm->mmap_sem);
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arg_start = mm->arg_start;
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arg_end = mm->arg_end;
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env_start = mm->env_start;
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env_end = mm->env_end;
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up_read(&mm->mmap_sem);
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BUG_ON(arg_start > arg_end);
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BUG_ON(env_start > env_end);
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len1 = arg_end - arg_start;
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len2 = env_end - env_start;
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/*
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* Rely on struct seq_operations::show() being called once
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* per internal buffer allocation. See single_open(), traverse().
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* Inherently racy -- command line shares address space
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* with code and data.
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*/
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BUG_ON(m->size < PAGE_SIZE);
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m->count += get_cmdline(task, m->buf, PAGE_SIZE);
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return 0;
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rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
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if (rv <= 0)
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goto out_free_page;
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rv = 0;
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if (c == '\0') {
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/* Command line (set of strings) occupies whole ARGV. */
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if (len1 <= *pos)
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goto out_free_page;
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p = arg_start + *pos;
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len = len1 - *pos;
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while (count > 0 && len > 0) {
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unsigned int _count;
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int nr_read;
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_count = min3(count, len, PAGE_SIZE);
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nr_read = access_remote_vm(mm, p, page, _count, 0);
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if (nr_read < 0)
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rv = nr_read;
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if (nr_read <= 0)
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goto out_free_page;
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if (copy_to_user(buf, page, nr_read)) {
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rv = -EFAULT;
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goto out_free_page;
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}
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p += nr_read;
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len -= nr_read;
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buf += nr_read;
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count -= nr_read;
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rv += nr_read;
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}
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} else {
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/*
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* Command line (1 string) occupies ARGV and maybe
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* extends into ENVP.
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*/
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if (len1 + len2 <= *pos)
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goto skip_argv_envp;
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if (len1 <= *pos)
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goto skip_argv;
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p = arg_start + *pos;
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len = len1 - *pos;
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while (count > 0 && len > 0) {
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unsigned int _count, l;
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int nr_read;
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bool final;
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_count = min3(count, len, PAGE_SIZE);
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nr_read = access_remote_vm(mm, p, page, _count, 0);
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if (nr_read < 0)
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rv = nr_read;
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if (nr_read <= 0)
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goto out_free_page;
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/*
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* Command line can be shorter than whole ARGV
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* even if last "marker" byte says it is not.
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*/
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final = false;
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l = strnlen(page, nr_read);
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if (l < nr_read) {
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nr_read = l;
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final = true;
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}
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if (copy_to_user(buf, page, nr_read)) {
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rv = -EFAULT;
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goto out_free_page;
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}
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p += nr_read;
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len -= nr_read;
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buf += nr_read;
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count -= nr_read;
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rv += nr_read;
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if (final)
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goto out_free_page;
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}
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skip_argv:
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/*
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* Command line (1 string) occupies ARGV and
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* extends into ENVP.
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*/
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if (len1 <= *pos) {
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p = env_start + *pos - len1;
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len = len1 + len2 - *pos;
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} else {
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p = env_start;
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len = len2;
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}
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while (count > 0 && len > 0) {
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unsigned int _count, l;
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int nr_read;
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bool final;
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_count = min3(count, len, PAGE_SIZE);
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nr_read = access_remote_vm(mm, p, page, _count, 0);
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if (nr_read < 0)
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rv = nr_read;
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if (nr_read <= 0)
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goto out_free_page;
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/* Find EOS. */
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final = false;
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l = strnlen(page, nr_read);
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if (l < nr_read) {
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nr_read = l;
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final = true;
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}
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if (copy_to_user(buf, page, nr_read)) {
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rv = -EFAULT;
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goto out_free_page;
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}
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p += nr_read;
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len -= nr_read;
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buf += nr_read;
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count -= nr_read;
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rv += nr_read;
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if (final)
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goto out_free_page;
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}
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skip_argv_envp:
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;
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}
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out_free_page:
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free_page((unsigned long)page);
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out_mmput:
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mmput(mm);
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if (rv > 0)
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*pos += rv;
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return rv;
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}
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static const struct file_operations proc_pid_cmdline_ops = {
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.read = proc_pid_cmdline_read,
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.llseek = generic_file_llseek,
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};
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static int proc_pid_auxv(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *task)
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{
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@ -2572,7 +2759,7 @@ static const struct pid_entry tgid_base_stuff[] = {
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#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
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ONE("syscall", S_IRUSR, proc_pid_syscall),
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#endif
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ONE("cmdline", S_IRUGO, proc_pid_cmdline),
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REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
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ONE("stat", S_IRUGO, proc_tgid_stat),
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ONE("statm", S_IRUGO, proc_pid_statm),
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REG("maps", S_IRUGO, proc_pid_maps_operations),
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@ -2918,7 +3105,7 @@ static const struct pid_entry tid_base_stuff[] = {
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#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
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ONE("syscall", S_IRUSR, proc_pid_syscall),
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#endif
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ONE("cmdline", S_IRUGO, proc_pid_cmdline),
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REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
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ONE("stat", S_IRUGO, proc_tid_stat),
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ONE("statm", S_IRUGO, proc_pid_statm),
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REG("maps", S_IRUGO, proc_tid_maps_operations),
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