From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/video/fbdev/savage/Makefile | 10 + drivers/video/fbdev/savage/savagefb-i2c.c | 241 +++ drivers/video/fbdev/savage/savagefb.h | 406 ++++ drivers/video/fbdev/savage/savagefb_accel.c | 137 ++ drivers/video/fbdev/savage/savagefb_driver.c | 2579 ++++++++++++++++++++++++++ 5 files changed, 3373 insertions(+) create mode 100644 drivers/video/fbdev/savage/Makefile create mode 100644 drivers/video/fbdev/savage/savagefb-i2c.c create mode 100644 drivers/video/fbdev/savage/savagefb.h create mode 100644 drivers/video/fbdev/savage/savagefb_accel.c create mode 100644 drivers/video/fbdev/savage/savagefb_driver.c (limited to 'drivers/video/fbdev/savage') diff --git a/drivers/video/fbdev/savage/Makefile b/drivers/video/fbdev/savage/Makefile new file mode 100644 index 000000000..3f6fcced1 --- /dev/null +++ b/drivers/video/fbdev/savage/Makefile @@ -0,0 +1,10 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Makefile for the S3 Savage framebuffer driver +# + +obj-$(CONFIG_FB_SAVAGE) += savagefb.o + +savagefb-y += savagefb_driver.o +savagefb-$(CONFIG_FB_SAVAGE_I2C) += savagefb-i2c.o +savagefb-$(CONFIG_FB_SAVAGE_ACCEL) += savagefb_accel.o diff --git a/drivers/video/fbdev/savage/savagefb-i2c.c b/drivers/video/fbdev/savage/savagefb-i2c.c new file mode 100644 index 000000000..80fa87e2a --- /dev/null +++ b/drivers/video/fbdev/savage/savagefb-i2c.c @@ -0,0 +1,241 @@ +/* + * linux/drivers/video/savage/savagefb-i2c.c - S3 Savage DDC2 + * + * Copyright 2004 Antonino A. Daplas + * + * Based partly on rivafb-i2c.c + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of this archive + * for more details. + */ + +#include +#include +#include +#include +#include +#include + +#include +#include "savagefb.h" + +#define SAVAGE_DDC 0x50 + +#define VGA_CR_IX 0x3d4 +#define VGA_CR_DATA 0x3d5 + +#define CR_SERIAL1 0xa0 /* I2C serial communications interface */ +#define MM_SERIAL1 0xff20 +#define CR_SERIAL2 0xb1 /* DDC2 monitor communications interface */ + +/* based on vt8365 documentation */ +#define PROSAVAGE_I2C_ENAB 0x10 +#define PROSAVAGE_I2C_SCL_OUT 0x01 +#define PROSAVAGE_I2C_SDA_OUT 0x02 +#define PROSAVAGE_I2C_SCL_IN 0x04 +#define PROSAVAGE_I2C_SDA_IN 0x08 + +#define SAVAGE4_I2C_ENAB 0x00000020 +#define SAVAGE4_I2C_SCL_OUT 0x00000001 +#define SAVAGE4_I2C_SDA_OUT 0x00000002 +#define SAVAGE4_I2C_SCL_IN 0x00000008 +#define SAVAGE4_I2C_SDA_IN 0x00000010 + +static void savage4_gpio_setscl(void *data, int val) +{ + struct savagefb_i2c_chan *chan = data; + unsigned int r; + + r = readl(chan->ioaddr + chan->reg); + if(val) + r |= SAVAGE4_I2C_SCL_OUT; + else + r &= ~SAVAGE4_I2C_SCL_OUT; + writel(r, chan->ioaddr + chan->reg); + readl(chan->ioaddr + chan->reg); /* flush posted write */ +} + +static void savage4_gpio_setsda(void *data, int val) +{ + struct savagefb_i2c_chan *chan = data; + + unsigned int r; + r = readl(chan->ioaddr + chan->reg); + if(val) + r |= SAVAGE4_I2C_SDA_OUT; + else + r &= ~SAVAGE4_I2C_SDA_OUT; + writel(r, chan->ioaddr + chan->reg); + readl(chan->ioaddr + chan->reg); /* flush posted write */ +} + +static int savage4_gpio_getscl(void *data) +{ + struct savagefb_i2c_chan *chan = data; + + return (0 != (readl(chan->ioaddr + chan->reg) & SAVAGE4_I2C_SCL_IN)); +} + +static int savage4_gpio_getsda(void *data) +{ + struct savagefb_i2c_chan *chan = data; + + return (0 != (readl(chan->ioaddr + chan->reg) & SAVAGE4_I2C_SDA_IN)); +} + +static void prosavage_gpio_setscl(void* data, int val) +{ + struct savagefb_i2c_chan *chan = data; + u32 r; + + r = VGArCR(chan->reg, chan->par); + r |= PROSAVAGE_I2C_ENAB; + if (val) { + r |= PROSAVAGE_I2C_SCL_OUT; + } else { + r &= ~PROSAVAGE_I2C_SCL_OUT; + } + + VGAwCR(chan->reg, r, chan->par); +} + +static void prosavage_gpio_setsda(void* data, int val) +{ + struct savagefb_i2c_chan *chan = data; + unsigned int r; + + r = VGArCR(chan->reg, chan->par); + r |= PROSAVAGE_I2C_ENAB; + if (val) { + r |= PROSAVAGE_I2C_SDA_OUT; + } else { + r &= ~PROSAVAGE_I2C_SDA_OUT; + } + + VGAwCR(chan->reg, r, chan->par); +} + +static int prosavage_gpio_getscl(void* data) +{ + struct savagefb_i2c_chan *chan = data; + + return (VGArCR(chan->reg, chan->par) & PROSAVAGE_I2C_SCL_IN) ? 1 : 0; +} + +static int prosavage_gpio_getsda(void* data) +{ + struct savagefb_i2c_chan *chan = data; + + return (VGArCR(chan->reg, chan->par) & PROSAVAGE_I2C_SDA_IN) ? 1 : 0; +} + +static int savage_setup_i2c_bus(struct savagefb_i2c_chan *chan, + const char *name) +{ + int rc = 0; + + if (chan->par) { + strcpy(chan->adapter.name, name); + chan->adapter.owner = THIS_MODULE; + chan->adapter.algo_data = &chan->algo; + chan->adapter.dev.parent = &chan->par->pcidev->dev; + chan->algo.udelay = 10; + chan->algo.timeout = 20; + chan->algo.data = chan; + + i2c_set_adapdata(&chan->adapter, chan); + + /* Raise SCL and SDA */ + chan->algo.setsda(chan, 1); + chan->algo.setscl(chan, 1); + udelay(20); + + rc = i2c_bit_add_bus(&chan->adapter); + + if (rc == 0) + dev_dbg(&chan->par->pcidev->dev, + "I2C bus %s registered.\n", name); + else + dev_warn(&chan->par->pcidev->dev, + "Failed to register I2C bus %s.\n", name); + } + + return rc; +} + +void savagefb_create_i2c_busses(struct fb_info *info) +{ + struct savagefb_par *par = info->par; + par->chan.par = par; + + switch (par->chip) { + case S3_PROSAVAGE: + case S3_PROSAVAGEDDR: + case S3_TWISTER: + par->chan.reg = CR_SERIAL2; + par->chan.ioaddr = par->mmio.vbase; + par->chan.algo.setsda = prosavage_gpio_setsda; + par->chan.algo.setscl = prosavage_gpio_setscl; + par->chan.algo.getsda = prosavage_gpio_getsda; + par->chan.algo.getscl = prosavage_gpio_getscl; + break; + case S3_SAVAGE4: + par->chan.reg = CR_SERIAL1; + if (par->pcidev->revision > 1 && !(VGArCR(0xa6, par) & 0x40)) + par->chan.reg = CR_SERIAL2; + par->chan.ioaddr = par->mmio.vbase; + par->chan.algo.setsda = prosavage_gpio_setsda; + par->chan.algo.setscl = prosavage_gpio_setscl; + par->chan.algo.getsda = prosavage_gpio_getsda; + par->chan.algo.getscl = prosavage_gpio_getscl; + break; + case S3_SAVAGE2000: + par->chan.reg = MM_SERIAL1; + par->chan.ioaddr = par->mmio.vbase; + par->chan.algo.setsda = savage4_gpio_setsda; + par->chan.algo.setscl = savage4_gpio_setscl; + par->chan.algo.getsda = savage4_gpio_getsda; + par->chan.algo.getscl = savage4_gpio_getscl; + break; + default: + par->chan.par = NULL; + } + + savage_setup_i2c_bus(&par->chan, "SAVAGE DDC2"); +} + +void savagefb_delete_i2c_busses(struct fb_info *info) +{ + struct savagefb_par *par = info->par; + + if (par->chan.par) + i2c_del_adapter(&par->chan.adapter); + + par->chan.par = NULL; +} + +int savagefb_probe_i2c_connector(struct fb_info *info, u8 **out_edid) +{ + struct savagefb_par *par = info->par; + u8 *edid; + + if (par->chan.par) + edid = fb_ddc_read(&par->chan.adapter); + else + edid = NULL; + + if (!edid) { + /* try to get from firmware */ + const u8 *e = fb_firmware_edid(info->device); + + if (e) + edid = kmemdup(e, EDID_LENGTH, GFP_KERNEL); + } + + *out_edid = edid; + + return (edid) ? 0 : 1; +} + +MODULE_LICENSE("GPL"); diff --git a/drivers/video/fbdev/savage/savagefb.h b/drivers/video/fbdev/savage/savagefb.h new file mode 100644 index 000000000..b6b8cc208 --- /dev/null +++ b/drivers/video/fbdev/savage/savagefb.h @@ -0,0 +1,406 @@ +/* + * linux/drivers/video/savagefb.h -- S3 Savage Framebuffer Driver + * + * Copyright (c) 2001 Denis Oliver Kropp + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file COPYING in the main directory of this + * archive for more details. + */ + + +#ifndef __SAVAGEFB_H__ +#define __SAVAGEFB_H__ + +#include +#include +#include +#include