[PATCH 0/3] usb: early: xhci-dbc: Some fixes and speed-up

[PATCH 0/3] usb: early: xhci-dbc: Some fixes and speed-up

[Christophe JAILLET]

While looking at places were using memcpy_and_pad() could be useful, I spotted
1 issue (patch 1) and 1 potential optimization (patch 2).
The use of memcpy_and_pad() is in patch 3.

Christophe JAILLET (3):
  usb: early: xhci-dbc: Fix a potential access to
  usb: early: xhci-dbc: Optimize early_xdbc_write()
  usb: early: xhci-dbc: Use memcpy_and_pad()

 drivers/usb/early/xhci-dbc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

-- 
2.34.1

[PATCH 1/3] usb: early: xhci-dbc: Fix a potential out-of-bound memory access

[Christophe JAILLET]

If xdbc_bulk_write() fails, the values in 'buf' can be anything. So the
string is not guaranteed to be NULL terminated when xdbc_trace() is called.

Reserve an extra byte, which will be zeroed automatically because 'buf' is
a static variable, in order to avoid troubles, should it happen.

Fixes: aeb9dd1de98c ("usb/early: Add driver for xhci debug capability")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/usb/early/xhci-dbc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 797047154820..f3e23be227d4 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -874,7 +874,8 @@ static int xdbc_bulk_write(const char *bytes, int size)
 
 static void early_xdbc_write(struct console *con, const char *str, u32 n)
 {
-	static char buf[XDBC_MAX_PACKET];
+	/* static variables are zeroed, so buf is always NULL terminated */
+	static char buf[XDBC_MAX_PACKET + 1];
 	int chunk, ret;
 	int use_cr = 0;
 
-- 
2.34.1

[PATCH 2/3] usb: early: xhci-dbc: Optimize early_xdbc_write()

[Christophe JAILLET]

There is no point in zeroing 'buf'.
It would be cleared only once, and if the 'while' loop is executed several
times, all but the first run would have a 'dirty' buffer.
Moreover, the size of the chunk is computed in the loop and this size is
passed to xdbc_bulk_write().

So remove this useless memset().

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Untested.
---
 drivers/usb/early/xhci-dbc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index f3e23be227d4..965a24e47c0f 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -881,7 +881,7 @@ static void early_xdbc_write(struct console *con, const char *str, u32 n)
 
 	if (!xdbc.xdbc_reg)
 		return;
-	memset(buf, 0, XDBC_MAX_PACKET);
+
 	while (n > 0) {
 		for (chunk = 0; chunk < XDBC_MAX_PACKET && n > 0; str++, chunk++, n--) {
 
-- 
2.34.1

[PATCH 3/3] usb: early: xhci-dbc: Use memcpy_and_pad()

[Christophe JAILLET]

Instead of zeroing some memory and then copying data in part or all of it,
use memcpy_and_pad().
This avoids writing some memory twice and should save a few cycles.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/usb/early/xhci-dbc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 965a24e47c0f..341408410ed9 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -499,8 +499,7 @@ static int xdbc_bulk_transfer(void *data, int size, bool read)
 		addr = xdbc.in_dma;
 		xdbc.flags |= XDBC_FLAGS_IN_PROCESS;
 	} else {
-		memset(xdbc.out_buf, 0, XDBC_MAX_PACKET);
-		memcpy(xdbc.out_buf, data, size);
+		memcpy_and_pad(xdbc.out_buf, XDBC_MAX_PACKET, data, size, 0);
 		addr = xdbc.out_dma;
 		xdbc.flags |= XDBC_FLAGS_OUT_PROCESS;
 	}
-- 
2.34.1