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Subject[PATCH 1/4] pagemap: Require reads of /proc/pid/pagemap to be multiples of 8 (v2 of series)
This matches the behavior of /proc/kpage{count,flags}, and simplifies
the logic a bit.

I also changed out and end in struct pagemapread to be u64* instead of
char*, which makes put_user work the way it was intended. (Before, it
was only copying the bottom byte of a pagemap entry, because the target
of the copy was a char*.)

Signed-off-by: Thomas Tuttle
---
fs/proc/task_mmu.c | 28 +++++++++-------------------
1 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 88717c0..01f9bff 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -496,7 +496,7 @@ const struct file_operations proc_clear_refs_operations = {
};

struct pagemapread {
- char __user *out, *end;
+ u64 __user *out, *end;
};

#define PM_ENTRY_BYTES sizeof(u64)
@@ -519,21 +519,11 @@ struct pagemapread {
static int add_to_pagemap(unsigned long addr, u64 pfn,
struct pagemapread *pm)
{
- /*
- * Make sure there's room in the buffer for an
- * entire entry. Otherwise, only copy part of
- * the pfn.
- */
- if (pm->out + PM_ENTRY_BYTES >= pm->end) {
- if (copy_to_user(pm->out, &pfn, pm->end - pm->out))
- return -EFAULT;
- pm->out = pm->end;
- return PM_END_OF_BUFFER;
- }
-
if (put_user(pfn, pm->out))
return -EFAULT;
- pm->out += PM_ENTRY_BYTES;
+ pm->out++;
+ if (pm->out >= pm->end)
+ return PM_END_OF_BUFFER;
return 0;
}

@@ -634,7 +624,7 @@ static ssize_t pagemap_read(struct file *file,
char __user * buf,

ret = -EINVAL;
/* file position must be aligned */
- if (*ppos % PM_ENTRY_BYTES)
+ if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
goto out_task;

ret = 0;
@@ -664,8 +654,8 @@ static ssize_t pagemap_read(struct file *file,
char __user * buf,
goto out_pages;
}

- pm.out = buf;
- pm.end = buf + count;
+ pm.out = (u64*)buf;
+ pm.end = (u64*)(buf + count);

if (!ptrace_may_attach(task)) {
ret = -EIO;
@@ -690,9 +680,9 @@ static ssize_t pagemap_read(struct file *file,
char __user * buf,
if (ret == PM_END_OF_BUFFER)
ret = 0;
/* don't need mmap_sem for these, but this looks cleaner */
- *ppos += pm.out - buf;
+ *ppos += (char*)pm.out - buf;
if (!ret)
- ret = pm.out - buf;
+ ret = (char*)pm.out - buf;
}

out_pages:
--
1.5.3.6

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