From: Kees Cook <keescook@chromium.org>
Date: Fri, 29 Jun 2018 11:47:40 -0700
Subject: drm/sun4i: Remove VLA usage
Git-commit: c51756d56e20a12476e4e192b332fac39c1550ca
Patch-mainline: v4.19-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
In the quest to remove all stack VLA usage from the kernel[1], this
switches to using a kmalloc allocation and moves all the size calculations
to the start to do an allocation. If an upper bounds on the mode timing
calculations could be determined, a fixed stack size could be used instead.
[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180629184740.GA37415@beast
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 107 +++++++++++++++++++--------------
1 file changed, 64 insertions(+), 43 deletions(-)
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -13,6 +13,7 @@
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/reset.h>
+#include <linux/slab.h>
#include <linux/phy/phy.h>
@@ -247,10 +248,8 @@ static u16 sun6i_dsi_crc_compute(u8 cons
return crc_ccitt(0xffff, buffer, len);
}
-static u16 sun6i_dsi_crc_repeat_compute(u8 pd, size_t len)
+static u16 sun6i_dsi_crc_repeat(u8 pd, u8 *buffer, size_t len)
{
- u8 buffer[len];
-
memset(buffer, pd, len);
return sun6i_dsi_crc_compute(buffer, len);
@@ -274,11 +273,11 @@ static u32 sun6i_dsi_build_blk0_pkt(u8 v
wc & 0xff, wc >> 8);
}
-static u32 sun6i_dsi_build_blk1_pkt(u16 pd, size_t len)
+static u32 sun6i_dsi_build_blk1_pkt(u16 pd, u8 *buffer, size_t len)
{
u32 val = SUN6I_DSI_BLK_PD(pd);
- return val | SUN6I_DSI_BLK_PF(sun6i_dsi_crc_repeat_compute(pd, len));
+ return val | SUN6I_DSI_BLK_PF(sun6i_dsi_crc_repeat(pd, buffer, len));
}
static void sun6i_dsi_inst_abort(struct sun6i_dsi *dsi)
@@ -452,6 +451,54 @@ static void sun6i_dsi_setup_timings(stru
struct mipi_dsi_device *device = dsi->device;
unsigned int Bpp = mipi_dsi_pixel_format_to_bpp(device->format) / 8;
u16 hbp, hfp, hsa, hblk, vblk;
+ size_t bytes;
+ u8 *buffer;
+
+ /* Do all timing calculations up front to allocate buffer space */
+
+ /*
+ * A sync period is composed of a blanking packet (4 bytes +
+ * payload + 2 bytes) and a sync event packet (4 bytes). Its
+ * minimal size is therefore 10 bytes
+ */
+#define HSA_PACKET_OVERHEAD 10
+ hsa = max((unsigned int)HSA_PACKET_OVERHEAD,
+ (mode->hsync_end - mode->hsync_start) * Bpp - HSA_PACKET_OVERHEAD);
+
+ /*
+ * The backporch is set using a blanking packet (4 bytes +
+ * payload + 2 bytes). Its minimal size is therefore 6 bytes
+ */
+#define HBP_PACKET_OVERHEAD 6
+ hbp = max((unsigned int)HBP_PACKET_OVERHEAD,
+ (mode->hsync_start - mode->hdisplay) * Bpp - HBP_PACKET_OVERHEAD);
+
+ /*
+ * The frontporch is set using a blanking packet (4 bytes +
+ * payload + 2 bytes). Its minimal size is therefore 6 bytes
+ */
+#define HFP_PACKET_OVERHEAD 6
+ hfp = max((unsigned int)HFP_PACKET_OVERHEAD,
+ (mode->htotal - mode->hsync_end) * Bpp - HFP_PACKET_OVERHEAD);
+
+ /*
+ * hblk seems to be the line + porches length.
+ */
+ hblk = mode->htotal * Bpp - hsa;
+
+ /*
+ * And I'm not entirely sure what vblk is about. The driver in
+ * Allwinner BSP is using a rather convoluted calculation
+ * there only for 4 lanes. However, using 0 (the !4 lanes
+ * case) even with a 4 lanes screen seems to work...
+ */
+ vblk = 0;
+
+ /* How many bytes do we need to send all payloads? */
+ bytes = max_t(size_t, max(max(hfp, hblk), max(hsa, hbp)), vblk);
+ buffer = kmalloc(bytes, GFP_KERNEL);
+ if (WARN_ON(!buffer))
+ return;
regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL_REG, 0);
@@ -485,63 +532,37 @@ static void sun6i_dsi_setup_timings(stru
SUN6I_DSI_BASIC_SIZE1_VACT(mode->vdisplay) |
SUN6I_DSI_BASIC_SIZE1_VT(mode->vtotal));
- /*
- * A sync period is composed of a blanking packet (4 bytes +
- * payload + 2 bytes) and a sync event packet (4 bytes). Its
- * minimal size is therefore 10 bytes
- */
-#define HSA_PACKET_OVERHEAD 10
- hsa = max((unsigned int)HSA_PACKET_OVERHEAD,
- (mode->hsync_end - mode->hsync_start) * Bpp - HSA_PACKET_OVERHEAD);
+ /* sync */
regmap_write(dsi->regs, SUN6I_DSI_BLK_HSA0_REG,
sun6i_dsi_build_blk0_pkt(device->channel, hsa));
regmap_write(dsi->regs, SUN6I_DSI_BLK_HSA1_REG,
- sun6i_dsi_build_blk1_pkt(0, hsa));
+ sun6i_dsi_build_blk1_pkt(0, buffer, hsa));
- /*
- * The backporch is set using a blanking packet (4 bytes +
- * payload + 2 bytes). Its minimal size is therefore 6 bytes
- */
-#define HBP_PACKET_OVERHEAD 6
- hbp = max((unsigned int)HBP_PACKET_OVERHEAD,
- (mode->hsync_start - mode->hdisplay) * Bpp - HBP_PACKET_OVERHEAD);
+ /* backporch */
regmap_write(dsi->regs, SUN6I_DSI_BLK_HBP0_REG,
sun6i_dsi_build_blk0_pkt(device->channel, hbp));
regmap_write(dsi->regs, SUN6I_DSI_BLK_HBP1_REG,
- sun6i_dsi_build_blk1_pkt(0, hbp));
+ sun6i_dsi_build_blk1_pkt(0, buffer, hbp));
- /*
- * The frontporch is set using a blanking packet (4 bytes +
- * payload + 2 bytes). Its minimal size is therefore 6 bytes
- */
-#define HFP_PACKET_OVERHEAD 6
- hfp = max((unsigned int)HFP_PACKET_OVERHEAD,
- (mode->htotal - mode->hsync_end) * Bpp - HFP_PACKET_OVERHEAD);
+ /* frontporch */
regmap_write(dsi->regs, SUN6I_DSI_BLK_HFP0_REG,
sun6i_dsi_build_blk0_pkt(device->channel, hfp));
regmap_write(dsi->regs, SUN6I_DSI_BLK_HFP1_REG,
- sun6i_dsi_build_blk1_pkt(0, hfp));
+ sun6i_dsi_build_blk1_pkt(0, buffer, hfp));
- /*
- * hblk seems to be the line + porches length.
- */
- hblk = mode->htotal * Bpp - hsa;
+ /* hblk */
regmap_write(dsi->regs, SUN6I_DSI_BLK_HBLK0_REG,
sun6i_dsi_build_blk0_pkt(device->channel, hblk));
regmap_write(dsi->regs, SUN6I_DSI_BLK_HBLK1_REG,
- sun6i_dsi_build_blk1_pkt(0, hblk));
+ sun6i_dsi_build_blk1_pkt(0, buffer, hblk));
- /*
- * And I'm not entirely sure what vblk is about. The driver in
- * Allwinner BSP is using a rather convoluted calculation
- * there only for 4 lanes. However, using 0 (the !4 lanes
- * case) even with a 4 lanes screen seems to work...
- */
- vblk = 0;
+ /* vblk */
regmap_write(dsi->regs, SUN6I_DSI_BLK_VBLK0_REG,
sun6i_dsi_build_blk0_pkt(device->channel, vblk));
regmap_write(dsi->regs, SUN6I_DSI_BLK_VBLK1_REG,
- sun6i_dsi_build_blk1_pkt(0, vblk));
+ sun6i_dsi_build_blk1_pkt(0, buffer, vblk));
+
+ kfree(buffer);
}
static int sun6i_dsi_start(struct sun6i_dsi *dsi,