[PATCH 1/2] fs/proc/kcore.c: Make bounce buffer global for read

From: Jiri Olsa
Date: Thu Sep 08 2016 - 03:57:16 EST


Next patch adds bounce buffer for ktext area, so it's
convenient to have single bounce buffer for both
vmalloc/module and ktext cases.

Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
fs/proc/kcore.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index a939f5ed7f89..bd3ac9dca252 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -430,6 +430,7 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
static ssize_t
read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
{
+ char *buf = file->private_data;
ssize_t acc = 0;
size_t size, tsz;
size_t elf_buflen;
@@ -500,18 +501,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
if (clear_user(buffer, tsz))
return -EFAULT;
} else if (is_vmalloc_or_module_addr((void *)start)) {
- char * elf_buf;
-
- elf_buf = kzalloc(tsz, GFP_KERNEL);
- if (!elf_buf)
- return -ENOMEM;
- vread(elf_buf, (char *)start, tsz);
+ vread(buf, (char *)start, tsz);
/* we have to zero-fill user buffer even if no read */
- if (copy_to_user(buffer, elf_buf, tsz)) {
- kfree(elf_buf);
+ if (copy_to_user(buffer, buf, tsz))
return -EFAULT;
- }
- kfree(elf_buf);
} else {
if (kern_addr_valid(start)) {
unsigned long n;
@@ -549,6 +542,11 @@ static int open_kcore(struct inode *inode, struct file *filp)
{
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
+
+ filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!filp->private_data)
+ return -ENOMEM;
+
if (kcore_need_update)
kcore_update_ram();
if (i_size_read(inode) != proc_root_kcore->size) {
@@ -559,10 +557,16 @@ static int open_kcore(struct inode *inode, struct file *filp)
return 0;
}

+static int release_kcore(struct inode *inode, struct file *file)
+{
+ kfree(file->private_data);
+ return 0;
+}

static const struct file_operations proc_kcore_operations = {
.read = read_kcore,
.open = open_kcore,
+ .release = release_kcore,
.llseek = default_llseek,
};

--
2.7.4