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Message-ID: <46405469.6060708@moving-picture.com>
Date: Tue, 08 May 2007 11:43:53 +0100
From: James Pearson <james-p@...ing-picture.com>
To: linux-kernel@...r.kernel.org
CC: Eric Dumazet <dada1@...mosbay.com>
Subject: Re: [PATCH] Don't truncate /proc/PID/environ at 4096 characters
Eric Dumazet wrote:
> On Fri, 04 May 2007 15:30:57 +0100
> James Pearson <james-p@...ing-picture.com> wrote:
>
>
>>/proc/PID/environ currently truncates at 4096 characters, patch based on
>>the /proc/PID/mem code.
>>
>>Signed-off-by: James Pearson <james-p@...ing-picture.com>
>>
>
> What about latency when reading one *big* environ ?
>
> Dont we need some cond_resched() test in the loop ?
environ_read() only ever reads a maximum of PAGE_SIZE bytes in the loop,
so would this make any difference when reading a big environ?
>>+
>>+static struct file_operations proc_environ_operations = {
>>+ .read = environ_read,
>>+};
>>+
>
>
> Please use the const qualifier here :
>
> static const struct file_operations ...
Thanks - fixed:
Signed-off-by: James Pearson <james-p@...ing-picture.com>
--- ./fs/proc/base.c.dist 2007-04-26 04:08:32.000000000 +0100
+++ ./fs/proc/base.c 2007-04-27 16:32:44.277664457 +0100
@@ -196,22 +196,6 @@
(task->state == TASK_STOPPED || task->state == TASK_TRACED) && \
security_ptrace(current,task) == 0))
-static int proc_pid_environ(struct task_struct *task, char * buffer)
-{
- int res = 0;
- struct mm_struct *mm = get_task_mm(task);
- if (mm) {
- unsigned int len = mm->env_end - mm->env_start;
- if (len > PAGE_SIZE)
- len = PAGE_SIZE;
- res = access_process_vm(task, mm->env_start, buffer,
len, 0);
- if (!ptrace_may_attach(task))
- res = -ESRCH;
- mmput(mm);
- }
- return res;
-}
-
static int proc_pid_cmdline(struct task_struct *task, char * buffer)
{
int res = 0;
@@ -653,6 +637,84 @@
.open = mem_open,
};
+static ssize_t environ_read(struct file * file, char __user * buf,
+ size_t count, loff_t *ppos)
+{
+ struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
+ char *page;
+ unsigned long src = *ppos;
+ int ret = -ESRCH;
+ struct mm_struct *mm;
+ size_t max_len;
+
+ if (!task)
+ goto out_no_task;
+
+ if (!ptrace_may_attach(task))
+ goto out;
+
+ ret = -ENOMEM;
+ page = (char *)__get_free_page(GFP_USER);
+ if (!page)
+ goto out;
+
+ ret = 0;
+
+ mm = get_task_mm(task);
+ if (!mm)
+ goto out_free;
+
+ max_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
+
+ while (count > 0) {
+ int this_len, retval;
+
+ this_len = mm->env_end - (mm->env_start + src);
+
+ if (this_len <= 0) {
+ break;
+ }
+
+ if (this_len > max_len)
+ this_len = max_len;
+
+ retval = access_process_vm(task, (mm->env_start + src),
page, this_len, 0);
+
+ if (!ptrace_may_attach(task)) {
+ ret = -ESRCH;
+ break;
+ }
+
+ if (retval <= 0) {
+ ret = retval;
+ break;
+ }
+
+ if (copy_to_user(buf, page, retval)) {
+ ret = -EFAULT;
+ break;
+ }
+
+ ret += retval;
+ src += retval;
+ buf += retval;
+ count -= retval;
+ }
+ *ppos = src;
+
+ mmput(mm);
+out_free:
+ free_page((unsigned long) page);
+out:
+ put_task_struct(task);
+out_no_task:
+ return ret;
+}
+
+static const struct file_operations proc_environ_operations = {
+ .read = environ_read,
+};
+
static ssize_t oom_adjust_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
@@ -1831,7 +1893,7 @@
static struct pid_entry tgid_base_stuff[] = {
DIR("task", S_IRUGO|S_IXUGO, task),
DIR("fd", S_IRUSR|S_IXUSR, fd),
- INF("environ", S_IRUSR, pid_environ),
+ REG("environ", S_IRUSR, environ),
INF("auxv", S_IRUSR, pid_auxv),
INF("status", S_IRUGO, pid_status),
INF("cmdline", S_IRUGO, pid_cmdline),
@@ -2113,7 +2175,7 @@
*/
static struct pid_entry tid_base_stuff[] = {
DIR("fd", S_IRUSR|S_IXUSR, fd),
- INF("environ", S_IRUSR, pid_environ),
+ REG("environ", S_IRUSR, environ),
INF("auxv", S_IRUSR, pid_auxv),
INF("status", S_IRUGO, pid_status),
INF("cmdline", S_IRUGO, pid_cmdline),
-
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