drm/ast: Fixed CVE for DP501

[Bug][DP501]
If ASPEED P2A (PCI to AHB) bridge is disabled and disallowed for
CVE_2019_6260 item3, and then the monitor's EDID is unable read through
Parade DP501.
The reason is the DP501's FW is mapped to BMC addressing space rather
than Host addressing space.
The resolution is that using "pci_iomap_range()" maps to DP501's FW that
stored on the end of FB (Frame Buffer).
In this case, FrameBuffer reserves the last 2MB used for the image of
DP501.
Signed-off-by: KuoHsiang Chou <kuohsiang_chou@aspeedtech.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210421085859.17761-1-kuohsiang_chou@aspeedtech.com

drivers/gpu/drm/ast/ast_dp501.c

@@ -189,6 +189,9 @@ bool ast_backup_fw(struct drm_device *dev, u8 *addr, u32 size)
 	u32 i, data;
 	u32 boot_address;
 
+	if (ast->config_mode != ast_use_p2a)
+		return false;
+
 	data = ast_mindwm(ast, 0x1e6e2100) & 0x01;
 	if (data) {
 		boot_address = get_fw_base(ast);
@@ -207,6 +210,9 @@ static bool ast_launch_m68k(struct drm_device *dev)
 	u8 *fw_addr = NULL;
 	u8 jreg;
 
+	if (ast->config_mode != ast_use_p2a)
+		return false;
+
 	data = ast_mindwm(ast, 0x1e6e2100) & 0x01;
 	if (!data) {
 
@@ -271,18 +277,47 @@ u8 ast_get_dp501_max_clk(struct drm_device *dev)
 	struct ast_private *ast = to_ast_private(dev);
 	u32 boot_address, offset, data;
 	u8 linkcap[4], linkrate, linklanes, maxclk = 0xff;
+	u32 *plinkcap;
 
+	if (ast->config_mode == ast_use_p2a) {
 		boot_address = get_fw_base(ast);
 
 		/* validate FW version */
-	offset = 0xf000;
+		offset = AST_DP501_GBL_VERSION;
 		data = ast_mindwm(ast, boot_address + offset);
-	if ((data & 0xf0) != 0x10) /* version: 1x */
+		if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1) /* version: 1x */
+			return maxclk;
+
+		/* Read Link Capability */
+		offset  = AST_DP501_LINKRATE;
+		plinkcap = (u32 *)linkcap;
+		*plinkcap  = ast_mindwm(ast, boot_address + offset);
+		if (linkcap[2] == 0) {
+			linkrate = linkcap[0];
+			linklanes = linkcap[1];
+			data = (linkrate == 0x0a) ? (90 * linklanes) : (54 * linklanes);
+			if (data > 0xff)
+				data = 0xff;
+			maxclk = (u8)data;
+		}
+	} else {
+		if (!ast->dp501_fw_buf)
+			return AST_DP501_DEFAULT_DCLK;	/* 1024x768 as default */
+
+		/* dummy read */
+		offset = 0x0000;
+		data = readl(ast->dp501_fw_buf + offset);
+
+		/* validate FW version */
+		offset = AST_DP501_GBL_VERSION;
+		data = readl(ast->dp501_fw_buf + offset);
+		if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1) /* version: 1x */
 			return maxclk;
 
 		/* Read Link Capability */
-	offset  = 0xf014;
-	*(u32 *)linkcap = ast_mindwm(ast, boot_address + offset);
+		offset = AST_DP501_LINKRATE;
+		plinkcap = (u32 *)linkcap;
+		*plinkcap = readl(ast->dp501_fw_buf + offset);
 		if (linkcap[2] == 0) {
 			linkrate = linkcap[0];
 			linklanes = linkcap[1];
@@ -291,6 +326,7 @@ u8 ast_get_dp501_max_clk(struct drm_device *dev)
 				data = 0xff;
 			maxclk = (u8)data;
 		}
+	}
 	return maxclk;
 }
 
@@ -298,26 +334,57 @@ bool ast_dp501_read_edid(struct drm_device *dev, u8 *ediddata)
 {
 	struct ast_private *ast = to_ast_private(dev);
 	u32 i, boot_address, offset, data;
+	u32 *pEDIDidx;
 
+	if (ast->config_mode == ast_use_p2a) {
 		boot_address = get_fw_base(ast);
 
 		/* validate FW version */
-	offset = 0xf000;
+		offset = AST_DP501_GBL_VERSION;
 		data = ast_mindwm(ast, boot_address + offset);
-	if ((data & 0xf0) != 0x10)
+		if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1)
 			return false;
 
 		/* validate PnP Monitor */
-	offset = 0xf010;
+		offset = AST_DP501_PNPMONITOR;
 		data = ast_mindwm(ast, boot_address + offset);
-	if (!(data & 0x01))
+		if (!(data & AST_DP501_PNP_CONNECTED))
 			return false;
 
 		/* Read EDID */
-	offset = 0xf020;
+		offset = AST_DP501_EDID_DATA;
 		for (i = 0; i < 128; i += 4) {
 			data = ast_mindwm(ast, boot_address + offset + i);
-		*(u32 *)(ediddata + i) = data;
+			pEDIDidx = (u32 *)(ediddata + i);
+			*pEDIDidx = data;
+		}
+	} else {
+		if (!ast->dp501_fw_buf)
+			return false;
+
+		/* dummy read */
+		offset = 0x0000;
+		data = readl(ast->dp501_fw_buf + offset);
+
+		/* validate FW version */
+		offset = AST_DP501_GBL_VERSION;
+		data = readl(ast->dp501_fw_buf + offset);
+		if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1)
+			return false;
+
+		/* validate PnP Monitor */
+		offset = AST_DP501_PNPMONITOR;
+		data = readl(ast->dp501_fw_buf + offset);
+		if (!(data & AST_DP501_PNP_CONNECTED))
+			return false;
+
+		/* Read EDID */
+		offset = AST_DP501_EDID_DATA;
+		for (i = 0; i < 128; i += 4) {
+			data = readl(ast->dp501_fw_buf + offset + i);
+			pEDIDidx = (u32 *)(ediddata + i);
+			*pEDIDidx = data;
+		}
 	}
 
 	return true;

drivers/gpu/drm/ast/ast_drv.h

@@ -150,6 +150,7 @@ struct ast_private {
 
 	void __iomem *regs;
 	void __iomem *ioregs;
+	void __iomem *dp501_fw_buf;
 
 	enum ast_chip chip;
 	bool vga2_clone;
@@ -325,6 +326,17 @@ int ast_mode_config_init(struct ast_private *ast);
 #define AST_MM_ALIGN_SHIFT 4
 #define AST_MM_ALIGN_MASK ((1 << AST_MM_ALIGN_SHIFT) - 1)
 
+#define AST_DP501_FW_VERSION_MASK	GENMASK(7, 4)
+#define AST_DP501_FW_VERSION_1		BIT(4)
+#define AST_DP501_PNP_CONNECTED		BIT(1)
+
+#define AST_DP501_DEFAULT_DCLK	65
+
+#define AST_DP501_GBL_VERSION	0xf000
+#define AST_DP501_PNPMONITOR	0xf010
+#define AST_DP501_LINKRATE	0xf014
+#define AST_DP501_EDID_DATA	0xf020
+
 int ast_mm_init(struct ast_private *ast);
 
 /* ast post */

drivers/gpu/drm/ast/ast_main.c

@@ -99,7 +99,7 @@ static void ast_detect_config_mode(struct drm_device *dev, u32 *scu_rev)
 	if (!(jregd0 & 0x80) || !(jregd1 & 0x10)) {
 		/* Double check it's actually working */
 		data = ast_read32(ast, 0xf004);
-		if (data != 0xFFFFFFFF) {
+		if ((data != 0xFFFFFFFF) && (data != 0x00)) {
 			/* P2A works, grab silicon revision */
 			ast->config_mode = ast_use_p2a;
 
@@ -411,6 +411,7 @@ struct ast_private *ast_device_create(const struct drm_driver *drv,
 		return ast;
 	dev = &ast->base;
 
+	dev->pdev = pdev;
 	pci_set_drvdata(pdev, dev);
 
 	ast->regs = pcim_iomap(pdev, 1, 0);
@@ -450,6 +451,14 @@ struct ast_private *ast_device_create(const struct drm_driver *drv,
 	if (ret)
 		return ERR_PTR(ret);
 
+	/* map reserved buffer */
+	ast->dp501_fw_buf = NULL;
+	if (dev->vram_mm->vram_size < pci_resource_len(dev->pdev, 0)) {
+		ast->dp501_fw_buf = pci_iomap_range(dev->pdev, 0, dev->vram_mm->vram_size, 0);
+		if (!ast->dp501_fw_buf)
+			drm_info(dev, "failed to map reserved buffer!\n");
+	}
+
 	ret = ast_mode_config_init(ast);
 	if (ret)
 		return ERR_PTR(ret);