在 2021/8/2 下午3:25, Jiri Slaby 写道:
Hi,
why is this 2/2? I seem (Lore neither) to find 1/2.
You didn't receive 1/2?
[PATCH 1/2] tty: hvc: pass DMA capable memory to put_chars()
https://lkml.org/lkml/2021/8/1/8 <https://lkml.org/lkml/2021/8/1/8>
On 01. 08. 21, 7:16, Xianting Tian wrote:
hvc framework will never pass stack memory to the put_chars() function,
Am I blind or missing something?
hvc_console_print(...)
{
char c[N_OUTBUF]
...
cons_ops[index]->put_chars(vtermnos[index], c, i);
The same here:
hvc_poll_put_char(..., char ch)
{
...
n = hp->ops->put_chars(hp->vtermno, &ch, 1);
AFAICS both of them *pass* a pointer to stack variable.
yes, I discussed the issue with Arnd before in below thread, you can
get the history, thanks
https://lkml.org/lkml/2021/7/27/494 <https://lkml.org/lkml/2021/7/27/494>
So the calling of kmemdup() is unnecessary, remove it.
Fixes: c4baad5029 ("virtio-console: avoid DMA from stack")
This patch doesn't "Fix" -- it reverts the commit. You should've CCed
the author too.
yes, we discussed ther issue in above thread, which we CCed the author.
Signed-off-by: Xianting Tian <xianting.t...@linux.alibaba.com>
---
drivers/char/virtio_console.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/drivers/char/virtio_console.c
b/drivers/char/virtio_console.c
index 7eaf303a7..4ed3ffb1d 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1117,8 +1117,6 @@ static int put_chars(u32 vtermno, const char
*buf, int count)
{
struct port *port;
struct scatterlist sg[1];
- void *data;
- int ret;
if (unlikely(early_put_chars))
return early_put_chars(vtermno, buf, count);
@@ -1127,14 +1125,8 @@ static int put_chars(u32 vtermno, const char
*buf, int count)
if (!port)
return -EPIPE;
- data = kmemdup(buf, count, GFP_ATOMIC);
- if (!data)
- return -ENOMEM;
-
- sg_init_one(sg, data, count);
- ret = __send_to_port(port, sg, 1, count, data, false);
- kfree(data);
- return ret;
+ sg_init_one(sg, buf, count);
+ return __send_to_port(port, sg, 1, count, (void *)buf, false);
}
/*
