linux-kernel - [PATCH V4 2/3] drm/vkms: Compute CRC without change input data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200511115524.22602-3-Rodrigo.Siqueira@amd.com>
Date:   Mon, 11 May 2020 07:55:23 -0400
From:   Rodrigo Siqueira <Rodrigo.Siqueira@....com>
To:     Brian Starkey <brian.starkey@....com>,
        Liviu Dudau <liviu.dudau@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        Simon Ser <contact@...rsion.fr>,
        Leandro Ribeiro <leandro.ribeiro@...labora.com>,
        Helen Koike <helen.koike@...labora.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
Subject: [PATCH V4 2/3] drm/vkms: Compute CRC without change input data

From: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>

The compute_crc() function is responsible for calculating the
framebuffer CRC value; due to the XRGB format, this function has to
ignore the alpha channel during the CRC computation. Therefore,
compute_crc() set zero to the alpha channel directly in the input
framebuffer, which is not a problem since this function receives a copy
of the original buffer. However, if we want to use this function in a
context without a buffer copy, it will change the initial value. This
patch makes compute_crc() calculate the CRC value without modifying the
input framebuffer.

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
---
 drivers/gpu/drm/vkms/vkms_composer.c | 31 +++++++++++++++++-----------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index 258e659ecfba..686d25e7b01d 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -9,33 +9,40 @@
 
 #include "vkms_drv.h"
 
+static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
+				 const struct vkms_composer *composer)
+{
+	int src_offset = composer->offset + (y * composer->pitch)
+					  + (x * composer->cpp);
+
+	return *(u32 *)&buffer[src_offset];
+}
+
 /**
  * compute_crc - Compute CRC value on output frame
  *
- * @vaddr_out: address to final framebuffer
+ * @vaddr: address to final framebuffer
  * @composer: framebuffer's metadata
  *
  * returns CRC value computed using crc32 on the visible portion of
  * the final framebuffer at vaddr_out
  */
-static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer)
+static uint32_t compute_crc(const u8 *vaddr,
+			    const struct vkms_composer *composer)
 {
-	int i, j, src_offset;
+	int x, y;
 	int x_src = composer->src.x1 >> 16;
 	int y_src = composer->src.y1 >> 16;
 	int h_src = drm_rect_height(&composer->src) >> 16;
 	int w_src = drm_rect_width(&composer->src) >> 16;
-	u32 crc = 0;
+	u32 crc = 0, pixel = 0;
 
-	for (i = y_src; i < y_src + h_src; ++i) {
-		for (j = x_src; j < x_src + w_src; ++j) {
-			src_offset = composer->offset
-				     + (i * composer->pitch)
-				     + (j * composer->cpp);
+	for (y = y_src; y < y_src + h_src; ++y) {
+		for (x = x_src; x < x_src + w_src; ++x) {
 			/* XRGB format ignores Alpha channel */
-			memset(vaddr_out + src_offset + 24, 0,  8);
-			crc = crc32_le(crc, vaddr_out + src_offset,
-				       sizeof(u32));
+			pixel = get_pixel_from_buffer(x, y, vaddr, composer);
+			bitmap_clear((void *)&pixel, 0, 8);
+			crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
 		}
 	}
 
-- 
2.26.2