x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

6 files changed, 791 insertions, 0 deletions

diff --git a/drivers/gpu/drm/aspeed/Kconfig b/drivers/gpu/drm/aspeed/Kconfig
new file mode 100644
index 000000000..6e68f20aa
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config DRM_ASPEED_GFX
+	tristate "ASPEED BMC Display Controller"
+	depends on DRM && OF
+	depends on (COMPILE_TEST || ARCH_ASPEED)
+	depends on MMU
+	select DRM_CLIENT_SELECTION
+	select DRM_KMS_HELPER
+	select DRM_GEM_DMA_HELPER
+	select DMA_CMA if HAVE_DMA_CONTIGUOUS
+	select CMA if HAVE_DMA_CONTIGUOUS
+	select MFD_SYSCON
+	help
+	  Chose this option if you have an ASPEED AST2500 SOC Display
+	  Controller (aka GFX).
+
+	  If M is selected this module will be called aspeed_gfx.
diff --git a/drivers/gpu/drm/aspeed/Makefile b/drivers/gpu/drm/aspeed/Makefile
new file mode 100644
index 000000000..a681ba3cc
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+aspeed_gfx-y := aspeed_gfx_drv.o aspeed_gfx_crtc.o aspeed_gfx_out.o
+
+obj-$(CONFIG_DRM_ASPEED_GFX) += aspeed_gfx.o
diff --git a/drivers/gpu/drm/aspeed/aspeed_gfx.h b/drivers/gpu/drm/aspeed/aspeed_gfx.h
new file mode 100644
index 000000000..4e6a442c3
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/aspeed_gfx.h
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* Copyright 2018 IBM Corporation */
+
+#include <drm/drm_device.h>
+#include <drm/drm_simple_kms_helper.h>
+
+struct aspeed_gfx {
+	struct drm_device		drm;
+	void __iomem			*base;
+	struct clk			*clk;
+	struct reset_control		*rst;
+	struct regmap			*scu;
+
+	u32				dac_reg;
+	u32				int_clr_reg;
+	u32				vga_scratch_reg;
+	u32				throd_val;
+	u32				scan_line_max;
+
+	struct drm_simple_display_pipe	pipe;
+	struct drm_connector		connector;
+};
+#define to_aspeed_gfx(x) container_of(x, struct aspeed_gfx, drm)
+
+int aspeed_gfx_create_pipe(struct drm_device *drm);
+int aspeed_gfx_create_output(struct drm_device *drm);
+
+#define CRT_CTRL1		0x60 /* CRT Control I */
+#define CRT_CTRL2		0x64 /* CRT Control II */
+#define CRT_STATUS		0x68 /* CRT Status */
+#define CRT_MISC		0x6c /* CRT Misc Setting */
+#define CRT_HORIZ0		0x70 /* CRT Horizontal Total & Display Enable End */
+#define CRT_HORIZ1		0x74 /* CRT Horizontal Retrace Start & End */
+#define CRT_VERT0		0x78 /* CRT Vertical Total & Display Enable End */
+#define CRT_VERT1		0x7C /* CRT Vertical Retrace Start & End */
+#define CRT_ADDR		0x80 /* CRT Display Starting Address */
+#define CRT_OFFSET		0x84 /* CRT Display Offset & Terminal Count */
+#define CRT_THROD		0x88 /* CRT Threshold */
+#define CRT_XSCALE		0x8C /* CRT Scaling-Up Factor */
+#define CRT_CURSOR0		0x90 /* CRT Hardware Cursor X & Y Offset */
+#define CRT_CURSOR1		0x94 /* CRT Hardware Cursor X & Y Position */
+#define CRT_CURSOR2		0x98 /* CRT Hardware Cursor Pattern Address */
+#define CRT_9C			0x9C
+#define CRT_OSD_H		0xA0 /* CRT OSD Horizontal Start/End */
+#define CRT_OSD_V		0xA4 /* CRT OSD Vertical Start/End */
+#define CRT_OSD_ADDR		0xA8 /* CRT OSD Pattern Address */
+#define CRT_OSD_DISP		0xAC /* CRT OSD Offset */
+#define CRT_OSD_THRESH		0xB0 /* CRT OSD Threshold & Alpha */
+#define CRT_B4			0xB4
+#define CRT_STS_V		0xB8 /* CRT Status V */
+#define CRT_SCRATCH		0xBC /* Scratchpad */
+#define CRT_BB0_ADDR		0xD0 /* CRT Display BB0 Starting Address */
+#define CRT_BB1_ADDR		0xD4 /* CRT Display BB1 Starting Address */
+#define CRT_BB_COUNT		0xD8 /* CRT Display BB Terminal Count */
+#define OSD_COLOR1		0xE0 /* OSD Color Palette Index 1 & 0 */
+#define OSD_COLOR2		0xE4 /* OSD Color Palette Index 3 & 2 */
+#define OSD_COLOR3		0xE8 /* OSD Color Palette Index 5 & 4 */
+#define OSD_COLOR4		0xEC /* OSD Color Palette Index 7 & 6 */
+#define OSD_COLOR5		0xF0 /* OSD Color Palette Index 9 & 8 */
+#define OSD_COLOR6		0xF4 /* OSD Color Palette Index 11 & 10 */
+#define OSD_COLOR7		0xF8 /* OSD Color Palette Index 13 & 12 */
+#define OSD_COLOR8		0xFC /* OSD Color Palette Index 15 & 14 */
+
+/* CTRL1 */
+#define CRT_CTRL_EN			BIT(0)
+#define CRT_CTRL_HW_CURSOR_EN		BIT(1)
+#define CRT_CTRL_OSD_EN			BIT(2)
+#define CRT_CTRL_INTERLACED		BIT(3)
+#define CRT_CTRL_COLOR_RGB565		(0 << 7)
+#define CRT_CTRL_COLOR_YUV444		(1 << 7)
+#define CRT_CTRL_COLOR_XRGB8888		(2 << 7)
+#define CRT_CTRL_COLOR_RGB888		(3 << 7)
+#define CRT_CTRL_COLOR_YUV444_2RGB	(5 << 7)
+#define CRT_CTRL_COLOR_YUV422		(7 << 7)
+#define CRT_CTRL_COLOR_MASK		GENMASK(9, 7)
+#define CRT_CTRL_HSYNC_NEGATIVE		BIT(16)
+#define CRT_CTRL_VSYNC_NEGATIVE		BIT(17)
+#define CRT_CTRL_VERTICAL_INTR_EN	BIT(30)
+#define CRT_CTRL_VERTICAL_INTR_STS	BIT(31)
+
+/* CTRL2 */
+#define CRT_CTRL_DAC_EN			BIT(0)
+#define CRT_CTRL_VBLANK_LINE(x)		(((x) << 20) & CRT_CTRL_VBLANK_LINE_MASK)
+#define CRT_CTRL_VBLANK_LINE_MASK	GENMASK(31, 20)
+
+/* CRT_HORIZ0 */
+#define CRT_H_TOTAL(x)			(x)
+#define CRT_H_DE(x)			((x) << 16)
+
+/* CRT_HORIZ1 */
+#define CRT_H_RS_START(x)		(x)
+#define CRT_H_RS_END(x)			((x) << 16)
+
+/* CRT_VIRT0 */
+#define CRT_V_TOTAL(x)			(x)
+#define CRT_V_DE(x)			((x) << 16)
+
+/* CRT_VIRT1 */
+#define CRT_V_RS_START(x)		(x)
+#define CRT_V_RS_END(x)			((x) << 16)
+
+/* CRT_OFFSET */
+#define CRT_DISP_OFFSET(x)		(x)
+#define CRT_TERM_COUNT(x)		((x) << 16)
+
+/* CRT_THROD */
+#define CRT_THROD_LOW(x)		(x)
+#define CRT_THROD_HIGH(x)		((x) << 8)
diff --git a/drivers/gpu/drm/aspeed/aspeed_gfx_crtc.c b/drivers/gpu/drm/aspeed/aspeed_gfx_crtc.c
new file mode 100644
index 000000000..7877a57b8
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/aspeed_gfx_crtc.c
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2018 IBM Corporation
+
+#include <linux/clk.h>
+#include <linux/reset.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_fb_dma_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_dma_helper.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_simple_kms_helper.h>
+#include <drm/drm_vblank.h>
+
+#include "aspeed_gfx.h"
+
+static struct aspeed_gfx *
+drm_pipe_to_aspeed_gfx(struct drm_simple_display_pipe *pipe)
+{
+	return container_of(pipe, struct aspeed_gfx, pipe);
+}
+
+static int aspeed_gfx_set_pixel_fmt(struct aspeed_gfx *priv, u32 *bpp)
+{
+	struct drm_crtc *crtc = &priv->pipe.crtc;
+	struct drm_device *drm = crtc->dev;
+	const u32 format = crtc->primary->state->fb->format->format;
+	u32 ctrl1;
+
+	ctrl1 = readl(priv->base + CRT_CTRL1);
+	ctrl1 &= ~CRT_CTRL_COLOR_MASK;
+
+	switch (format) {
+	case DRM_FORMAT_RGB565:
+		dev_dbg(drm->dev, "Setting up RGB565 mode\n");
+		ctrl1 |= CRT_CTRL_COLOR_RGB565;
+		*bpp = 16;
+		break;
+	case DRM_FORMAT_XRGB8888:
+		dev_dbg(drm->dev, "Setting up XRGB8888 mode\n");
+		ctrl1 |= CRT_CTRL_COLOR_XRGB8888;
+		*bpp = 32;
+		break;
+	default:
+		dev_err(drm->dev, "Unhandled pixel format %08x\n", format);
+		return -EINVAL;
+	}
+
+	writel(ctrl1, priv->base + CRT_CTRL1);
+
+	return 0;
+}
+
+static void aspeed_gfx_enable_controller(struct aspeed_gfx *priv)
+{
+	u32 ctrl1 = readl(priv->base + CRT_CTRL1);
+	u32 ctrl2 = readl(priv->base + CRT_CTRL2);
+
+	/* Set DAC source for display output to Graphics CRT (GFX) */
+	regmap_update_bits(priv->scu, priv->dac_reg, BIT(16), BIT(16));
+
+	writel(ctrl1 | CRT_CTRL_EN, priv->base + CRT_CTRL1);
+	writel(ctrl2 | CRT_CTRL_DAC_EN, priv->base + CRT_CTRL2);
+}
+
+static void aspeed_gfx_disable_controller(struct aspeed_gfx *priv)
+{
+	u32 ctrl1 = readl(priv->base + CRT_CTRL1);
+	u32 ctrl2 = readl(priv->base + CRT_CTRL2);
+
+	writel(ctrl1 & ~CRT_CTRL_EN, priv->base + CRT_CTRL1);
+	writel(ctrl2 & ~CRT_CTRL_DAC_EN, priv->base + CRT_CTRL2);
+
+	regmap_update_bits(priv->scu, priv->dac_reg, BIT(16), 0);
+}
+
+static void aspeed_gfx_crtc_mode_set_nofb(struct aspeed_gfx *priv)
+{
+	struct drm_display_mode *m = &priv->pipe.crtc.state->adjusted_mode;
+	u32 ctrl1, d_offset, t_count, bpp;
+	int err;
+
+	err = aspeed_gfx_set_pixel_fmt(priv, &bpp);
+	if (err)
+		return;
+
+#if 0
+	/* TODO: we have only been able to test with the 40MHz USB clock. The
+	 * clock is fixed, so we cannot adjust it here. */
+	clk_set_rate(priv->pixel_clk, m->crtc_clock * 1000);
+#endif
+
+	ctrl1 = readl(priv->base + CRT_CTRL1);
+	ctrl1 &= ~(CRT_CTRL_INTERLACED |
+			CRT_CTRL_HSYNC_NEGATIVE |
+			CRT_CTRL_VSYNC_NEGATIVE);
+
+	if (m->flags & DRM_MODE_FLAG_INTERLACE)
+		ctrl1 |= CRT_CTRL_INTERLACED;
+
+	if (!(m->flags & DRM_MODE_FLAG_PHSYNC))
+		ctrl1 |= CRT_CTRL_HSYNC_NEGATIVE;
+
+	if (!(m->flags & DRM_MODE_FLAG_PVSYNC))
+		ctrl1 |= CRT_CTRL_VSYNC_NEGATIVE;
+
+	writel(ctrl1, priv->base + CRT_CTRL1);
+
+	/* Horizontal timing */
+	writel(CRT_H_TOTAL(m->htotal - 1) | CRT_H_DE(m->hdisplay - 1),
+			priv->base + CRT_HORIZ0);
+	writel(CRT_H_RS_START(m->hsync_start - 1) | CRT_H_RS_END(m->hsync_end),
+			priv->base + CRT_HORIZ1);
+
+
+	/* Vertical timing */
+	writel(CRT_V_TOTAL(m->vtotal - 1) | CRT_V_DE(m->vdisplay - 1),
+			priv->base + CRT_VERT0);
+	writel(CRT_V_RS_START(m->vsync_start) | CRT_V_RS_END(m->vsync_end),
+			priv->base + CRT_VERT1);
+
+	/*
+	 * Display Offset: address difference between consecutive scan lines
+	 * Terminal Count: memory size of one scan line
+	 */
+	d_offset = m->hdisplay * bpp / 8;
+	t_count = DIV_ROUND_UP(m->hdisplay * bpp, priv->scan_line_max);
+
+	writel(CRT_DISP_OFFSET(d_offset) | CRT_TERM_COUNT(t_count),
+			priv->base + CRT_OFFSET);
+
+	/*
+	 * Threshold: FIFO thresholds of refill and stop (16 byte chunks
+	 * per line, rounded up)
+	 */
+	writel(priv->throd_val, priv->base + CRT_THROD);
+}
+
+static void aspeed_gfx_pipe_enable(struct drm_simple_display_pipe *pipe,
+			      struct drm_crtc_state *crtc_state,
+			      struct drm_plane_state *plane_state)
+{
+	struct aspeed_gfx *priv = drm_pipe_to_aspeed_gfx(pipe);
+	struct drm_crtc *crtc = &pipe->crtc;
+
+	aspeed_gfx_crtc_mode_set_nofb(priv);
+	aspeed_gfx_enable_controller(priv);
+	drm_crtc_vblank_on(crtc);
+}
+
+static void aspeed_gfx_pipe_disable(struct drm_simple_display_pipe *pipe)
+{
+	struct aspeed_gfx *priv = drm_pipe_to_aspeed_gfx(pipe);
+	struct drm_crtc *crtc = &pipe->crtc;
+
+	drm_crtc_vblank_off(crtc);
+	aspeed_gfx_disable_controller(priv);
+}
+
+static void aspeed_gfx_pipe_update(struct drm_simple_display_pipe *pipe,
+				   struct drm_plane_state *plane_state)
+{
+	struct aspeed_gfx *priv = drm_pipe_to_aspeed_gfx(pipe);
+	struct drm_crtc *crtc = &pipe->crtc;
+	struct drm_framebuffer *fb = pipe->plane.state->fb;
+	struct drm_pending_vblank_event *event;
+	struct drm_gem_dma_object *gem;
+
+	spin_lock_irq(&crtc->dev->event_lock);
+	event = crtc->state->event;
+	if (event) {
+		crtc->state->event = NULL;
+
+		if (drm_crtc_vblank_get(crtc) == 0)
+			drm_crtc_arm_vblank_event(crtc, event);
+		else
+			drm_crtc_send_vblank_event(crtc, event);
+	}
+	spin_unlock_irq(&crtc->dev->event_lock);
+
+	if (!fb)
+		return;
+
+	gem = drm_fb_dma_get_gem_obj(fb, 0);
+	if (!gem)
+		return;
+	writel(gem->dma_addr, priv->base + CRT_ADDR);
+}
+
+static int aspeed_gfx_enable_vblank(struct drm_simple_display_pipe *pipe)
+{
+	struct aspeed_gfx *priv = drm_pipe_to_aspeed_gfx(pipe);
+	u32 reg = readl(priv->base + CRT_CTRL1);
+
+	/* Clear pending VBLANK IRQ */
+	writel(reg | CRT_CTRL_VERTICAL_INTR_STS, priv->base + CRT_CTRL1);
+
+	reg |= CRT_CTRL_VERTICAL_INTR_EN;
+	writel(reg, priv->base + CRT_CTRL1);
+
+	return 0;
+}
+
+static void aspeed_gfx_disable_vblank(struct drm_simple_display_pipe *pipe)
+{
+	struct aspeed_gfx *priv = drm_pipe_to_aspeed_gfx(pipe);
+	u32 reg = readl(priv->base + CRT_CTRL1);
+
+	reg &= ~CRT_CTRL_VERTICAL_INTR_EN;
+	writel(reg, priv->base + CRT_CTRL1);
+
+	/* Clear pending VBLANK IRQ */
+	writel(reg | CRT_CTRL_VERTICAL_INTR_STS, priv->base + CRT_CTRL1);
+}
+
+static const struct drm_simple_display_pipe_funcs aspeed_gfx_funcs = {
+	.enable		= aspeed_gfx_pipe_enable,
+	.disable	= aspeed_gfx_pipe_disable,
+	.update		= aspeed_gfx_pipe_update,
+	.enable_vblank	= aspeed_gfx_enable_vblank,
+	.disable_vblank	= aspeed_gfx_disable_vblank,
+};
+
+static const uint32_t aspeed_gfx_formats[] = {
+	DRM_FORMAT_XRGB8888,
+	DRM_FORMAT_RGB565,
+};
+
+int aspeed_gfx_create_pipe(struct drm_device *drm)
+{
+	struct aspeed_gfx *priv = to_aspeed_gfx(drm);
+
+	return drm_simple_display_pipe_init(drm, &priv->pipe, &aspeed_gfx_funcs,
+					    aspeed_gfx_formats,
+					    ARRAY_SIZE(aspeed_gfx_formats),
+					    NULL,
+					    &priv->connector);
+}
diff --git a/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c b/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c
new file mode 100644
index 000000000..d4577663a
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/aspeed_gfx_drv.c
@@ -0,0 +1,379 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2018 IBM Corporation
+
+#include <linux/clk.h>
+#include <linux/dma-mapping.h>
+#include <linux/irq.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+
+#include <drm/clients/drm_client_setup.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_device.h>
+#include <drm/drm_fbdev_dma.h>
+#include <drm/drm_gem_dma_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_module.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_simple_kms_helper.h>
+#include <drm/drm_vblank.h>
+#include <drm/drm_drv.h>
+
+#include "aspeed_gfx.h"
+
+/**
+ * DOC: ASPEED GFX Driver
+ *
+ * This driver is for the ASPEED BMC SoC's 'GFX' display hardware, also called
+ * the 'SOC Display Controller' in the datasheet. This driver runs on the ARM
+ * based BMC systems, unlike the ast driver which runs on a host CPU and is for
+ * a PCIe graphics device.
+ *
+ * The AST2500 supports a total of 3 output paths:
+ *
+ *   1. VGA output, the output target can choose either or both to the DAC
+ *   or DVO interface.
+ *
+ *   2. Graphics CRT output, the output target can choose either or both to
+ *   the DAC or DVO interface.
+ *
+ *   3. Video input from DVO, the video input can be used for video engine
+ *   capture or DAC display output.
+ *
+ * Output options are selected in SCU2C.
+ *
+ * The "VGA mode" device is the PCI attached controller. The "Graphics CRT"
+ * is the ARM's internal display controller.
+ *
+ * The driver only supports a simple configuration consisting of a 40MHz
+ * pixel clock, fixed by hardware limitations, and the VGA output path.
+ *
+ * The driver was written with the 'AST2500 Software Programming Guide' v17,
+ * which is available under NDA from ASPEED.
+ */
+
+struct aspeed_gfx_config {
+	u32 dac_reg;		/* DAC register in SCU */
+	u32 int_clear_reg;	/* Interrupt clear register */
+	u32 vga_scratch_reg;	/* VGA scratch register in SCU */
+	u32 throd_val;		/* Default Threshold Seting */
+	u32 scan_line_max;	/* Max memory size of one scan line */
+};
+
+static const struct aspeed_gfx_config ast2400_config = {
+	.dac_reg = 0x2c,
+	.int_clear_reg = 0x60,
+	.vga_scratch_reg = 0x50,
+	.throd_val = CRT_THROD_LOW(0x1e) | CRT_THROD_HIGH(0x12),
+	.scan_line_max = 64,
+};
+
+static const struct aspeed_gfx_config ast2500_config = {
+	.dac_reg = 0x2c,
+	.int_clear_reg = 0x60,
+	.vga_scratch_reg = 0x50,
+	.throd_val = CRT_THROD_LOW(0x24) | CRT_THROD_HIGH(0x3c),
+	.scan_line_max = 128,
+};
+
+static const struct aspeed_gfx_config ast2600_config = {
+	.dac_reg = 0xc0,
+	.int_clear_reg = 0x68,
+	.vga_scratch_reg = 0x50,
+	.throd_val = CRT_THROD_LOW(0x50) | CRT_THROD_HIGH(0x70),
+	.scan_line_max = 128,
+};
+
+static const struct of_device_id aspeed_gfx_match[] = {
+	{ .compatible = "aspeed,ast2400-gfx", .data = &ast2400_config },
+	{ .compatible = "aspeed,ast2500-gfx", .data = &ast2500_config },
+	{ .compatible = "aspeed,ast2600-gfx", .data = &ast2600_config },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, aspeed_gfx_match);
+
+static const struct drm_mode_config_funcs aspeed_gfx_mode_config_funcs = {
+	.fb_create		= drm_gem_fb_create,
+	.atomic_check		= drm_atomic_helper_check,
+	.atomic_commit		= drm_atomic_helper_commit,
+};
+
+static int aspeed_gfx_setup_mode_config(struct drm_device *drm)
+{
+	int ret;
+
+	ret = drmm_mode_config_init(drm);
+	if (ret)
+		return ret;
+
+	drm->mode_config.min_width = 0;
+	drm->mode_config.min_height = 0;
+	drm->mode_config.max_width = 800;
+	drm->mode_config.max_height = 600;
+	drm->mode_config.funcs = &aspeed_gfx_mode_config_funcs;
+
+	return ret;
+}
+
+static irqreturn_t aspeed_gfx_irq_handler(int irq, void *data)
+{
+	struct drm_device *drm = data;
+	struct aspeed_gfx *priv = to_aspeed_gfx(drm);
+	u32 reg;
+
+	reg = readl(priv->base + CRT_CTRL1);
+
+	if (reg & CRT_CTRL_VERTICAL_INTR_STS) {
+		drm_crtc_handle_vblank(&priv->pipe.crtc);
+		writel(reg, priv->base + priv->int_clr_reg);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int aspeed_gfx_load(struct drm_device *drm)
+{
+	struct platform_device *pdev = to_platform_device(drm->dev);
+	struct aspeed_gfx *priv = to_aspeed_gfx(drm);
+	struct device_node *np = pdev->dev.of_node;
+	const struct aspeed_gfx_config *config;
+	int ret;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	config = device_get_match_data(&pdev->dev);
+	if (!config)
+		return -EINVAL;
+
+	priv->dac_reg = config->dac_reg;
+	priv->int_clr_reg = config->int_clear_reg;
+	priv->vga_scratch_reg = config->vga_scratch_reg;
+	priv->throd_val = config->throd_val;
+	priv->scan_line_max = config->scan_line_max;
+
+	priv->scu = syscon_regmap_lookup_by_phandle(np, "syscon");
+	if (IS_ERR(priv->scu)) {
+		priv->scu = syscon_regmap_lookup_by_compatible("aspeed,ast2500-scu");
+		if (IS_ERR(priv->scu)) {
+			dev_err(&pdev->dev, "failed to find SCU regmap\n");
+			return PTR_ERR(priv->scu);
+		}
+	}
+
+	ret = of_reserved_mem_device_init(drm->dev);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"failed to initialize reserved mem: %d\n", ret);
+		return ret;
+	}
+
+	ret = dma_set_mask_and_coherent(drm->dev, DMA_BIT_MASK(32));
+	if (ret) {
+		dev_err(&pdev->dev, "failed to set DMA mask: %d\n", ret);
+		return ret;
+	}
+
+	priv->rst = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(priv->rst)) {
+		dev_err(&pdev->dev,
+			"missing or invalid reset controller device tree entry");
+		return PTR_ERR(priv->rst);
+	}
+	reset_control_deassert(priv->rst);
+
+	priv->clk = devm_clk_get(drm->dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		dev_err(&pdev->dev,
+			"missing or invalid clk device tree entry");
+		return PTR_ERR(priv->clk);
+	}
+	clk_prepare_enable(priv->clk);
+
+	/* Sanitize control registers */
+	writel(0, priv->base + CRT_CTRL1);
+	writel(0, priv->base + CRT_CTRL2);
+
+	ret = aspeed_gfx_setup_mode_config(drm);
+	if (ret < 0)
+		return ret;
+
+	ret = drm_vblank_init(drm, 1);
+	if (ret < 0) {
+		dev_err(drm->dev, "Failed to initialise vblank\n");
+		return ret;
+	}
+
+	ret = aspeed_gfx_create_output(drm);
+	if (ret < 0) {
+		dev_err(drm->dev, "Failed to create outputs\n");
+		return ret;
+	}
+
+	ret = aspeed_gfx_create_pipe(drm);
+	if (ret < 0) {
+		dev_err(drm->dev, "Cannot setup simple display pipe\n");
+		return ret;
+	}
+
+	ret = devm_request_irq(drm->dev, platform_get_irq(pdev, 0),
+			       aspeed_gfx_irq_handler, 0, "aspeed gfx", drm);
+	if (ret < 0) {
+		dev_err(drm->dev, "Failed to install IRQ handler\n");
+		return ret;
+	}
+
+	drm_mode_config_reset(drm);
+
+	return 0;
+}
+
+static void aspeed_gfx_unload(struct drm_device *drm)
+{
+	drm_kms_helper_poll_fini(drm);
+}
+
+DEFINE_DRM_GEM_DMA_FOPS(fops);
+
+static const struct drm_driver aspeed_gfx_driver = {
+	.driver_features        = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
+	DRM_GEM_DMA_DRIVER_OPS,
+	DRM_FBDEV_DMA_DRIVER_OPS,
+	.fops = &fops,
+	.name = "aspeed-gfx-drm",
+	.desc = "ASPEED GFX DRM",
+	.major = 1,
+	.minor = 0,
+};
+
+static ssize_t dac_mux_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct aspeed_gfx *priv = dev_get_drvdata(dev);
+	u32 val;
+	int rc;
+
+	rc = kstrtou32(buf, 0, &val);
+	if (rc)
+		return rc;
+
+	if (val > 3)
+		return -EINVAL;
+
+	rc = regmap_update_bits(priv->scu, priv->dac_reg, 0x30000, val << 16);
+	if (rc < 0)
+		return 0;
+
+	return count;
+}
+
+static ssize_t dac_mux_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct aspeed_gfx *priv = dev_get_drvdata(dev);
+	u32 reg;
+	int rc;
+
+	rc = regmap_read(priv->scu, priv->dac_reg, &reg);
+	if (rc)
+		return rc;
+
+	return sprintf(buf, "%u\n", (reg >> 16) & 0x3);
+}
+static DEVICE_ATTR_RW(dac_mux);
+
+static ssize_t
+vga_pw_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct aspeed_gfx *priv = dev_get_drvdata(dev);
+	u32 reg;
+	int rc;
+
+	rc = regmap_read(priv->scu, priv->vga_scratch_reg, &reg);
+	if (rc)
+		return rc;
+
+	return sprintf(buf, "%u\n", reg);
+}
+static DEVICE_ATTR_RO(vga_pw);
+
+static struct attribute *aspeed_sysfs_entries[] = {
+	&dev_attr_vga_pw.attr,
+	&dev_attr_dac_mux.attr,
+	NULL,
+};
+
+static struct attribute_group aspeed_sysfs_attr_group = {
+	.attrs = aspeed_sysfs_entries,
+};
+
+static int aspeed_gfx_probe(struct platform_device *pdev)
+{
+	struct aspeed_gfx *priv;
+	int ret;
+
+	priv = devm_drm_dev_alloc(&pdev->dev, &aspeed_gfx_driver,
+				  struct aspeed_gfx, drm);
+	if (IS_ERR(priv))
+		return PTR_ERR(priv);
+
+	ret = aspeed_gfx_load(&priv->drm);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	ret = sysfs_create_group(&pdev->dev.kobj, &aspeed_sysfs_attr_group);
+	if (ret)
+		return ret;
+
+	ret = drm_dev_register(&priv->drm, 0);
+	if (ret)
+		goto err_unload;
+
+	drm_client_setup(&priv->drm, NULL);
+	return 0;
+
+err_unload:
+	sysfs_remove_group(&pdev->dev.kobj, &aspeed_sysfs_attr_group);
+	aspeed_gfx_unload(&priv->drm);
+
+	return ret;
+}
+
+static void aspeed_gfx_remove(struct platform_device *pdev)
+{
+	struct drm_device *drm = platform_get_drvdata(pdev);
+
+	sysfs_remove_group(&pdev->dev.kobj, &aspeed_sysfs_attr_group);
+	drm_dev_unregister(drm);
+	aspeed_gfx_unload(drm);
+	drm_atomic_helper_shutdown(drm);
+}
+
+static void aspeed_gfx_shutdown(struct platform_device *pdev)
+{
+	drm_atomic_helper_shutdown(platform_get_drvdata(pdev));
+}
+
+static struct platform_driver aspeed_gfx_platform_driver = {
+	.probe		= aspeed_gfx_probe,
+	.remove		= aspeed_gfx_remove,
+	.shutdown	= aspeed_gfx_shutdown,
+	.driver = {
+		.name = "aspeed_gfx",
+		.of_match_table = aspeed_gfx_match,
+	},
+};
+
+drm_module_platform_driver(aspeed_gfx_platform_driver);
+
+MODULE_AUTHOR("Joel Stanley <joel@jms.id.au>");
+MODULE_DESCRIPTION("ASPEED BMC DRM/KMS driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/gpu/drm/aspeed/aspeed_gfx_out.c b/drivers/gpu/drm/aspeed/aspeed_gfx_out.c
new file mode 100644
index 000000000..78775e0c8
--- /dev/null
+++ b/drivers/gpu/drm/aspeed/aspeed_gfx_out.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2018 IBM Corporation
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_edid.h>
+#include <drm/drm_probe_helper.h>
+
+#include "aspeed_gfx.h"
+
+static int aspeed_gfx_get_modes(struct drm_connector *connector)
+{
+	return drm_add_modes_noedid(connector, 800, 600);
+}
+
+static const struct
+drm_connector_helper_funcs aspeed_gfx_connector_helper_funcs = {
+	.get_modes = aspeed_gfx_get_modes,
+};
+
+static const struct drm_connector_funcs aspeed_gfx_connector_funcs = {
+	.fill_modes		= drm_helper_probe_single_connector_modes,
+	.destroy		= drm_connector_cleanup,
+	.reset			= drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state	= drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state	= drm_atomic_helper_connector_destroy_state,
+};
+
+int aspeed_gfx_create_output(struct drm_device *drm)
+{
+	struct aspeed_gfx *priv = to_aspeed_gfx(drm);
+	int ret;
+
+	priv->connector.dpms = DRM_MODE_DPMS_OFF;
+	priv->connector.polled = 0;
+	drm_connector_helper_add(&priv->connector,
+				 &aspeed_gfx_connector_helper_funcs);
+	ret = drm_connector_init(drm, &priv->connector,
+				 &aspeed_gfx_connector_funcs,
+				 DRM_MODE_CONNECTOR_Unknown);
+	return ret;
+}