util/e6400-flash-unlock: Rename to dell-flash-unlock

This more accurately describes the scope of the utility.

Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>

6 files changed, 461 insertions, 0 deletions

diff --git a/util/dell-flash-unlock/COPYING b/util/dell-flash-unlock/COPYING
new file mode 100644
index 0000000..bf82341
--- /dev/null
+++ b/util/dell-flash-unlock/COPYING
@@ -0,0 +1,19 @@
+Copyright (c) 2023 Nicholas Chin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/util/dell-flash-unlock/Makefile b/util/dell-flash-unlock/Makefile
new file mode 100644
index 0000000..fae52de
--- /dev/null
+++ b/util/dell-flash-unlock/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: MIT
+# SPDX-FileCopyrightText: 2023 Nicholas Chin
+
+CC=cc
+CFLAGS=-Wall -Wextra -Werror -O2 -pedantic
+ifeq ($(shell uname), OpenBSD)
+	CFLAGS += -l$(shell uname -p)
+endif
+SRCS=dell_flash_unlock.c accessors.c
+
+all: $(SRCS) accessors.h
+	$(CC) $(CFLAGS) $(SRCS) -o dell_flash_unlock
+
+clean:
+	rm -f dell_flash_unlock
diff --git a/util/dell-flash-unlock/README.md b/util/dell-flash-unlock/README.md
new file mode 100644
index 0000000..ba45ddc
--- /dev/null
+++ b/util/dell-flash-unlock/README.md
@@ -0,0 +1,102 @@
+# Dell Laptop Internal Flashing
+
+This utility allows you to use flashrom's internal programmer to program the
+entire BIOS flash chip from software while still running the original Dell
+BIOS, which normally restricts software writes to the flash chip. It seems like
+this works on any Dell laptop that has an EC similar to the SMSC MEC5035 on the
+E6400, which mainly seem to be the Latitude and Precision lines starting from
+around 2008 (E6400 era).
+
+## TL;DR
+Run `make` to compile the utility, and then run `sudo ./dell_flash_unlock` and
+follow the directions it outputs.
+
+## Confirmed supported devices
+- Latitude E6400
+- Latitude E6410
+- Latitude E4310
+- Latitude E6430
+- Precision M6800
+
+It is likely that any other Latitude/Precision laptops from the same era as
+devices specifically mentioned in the above list will work as Dell seems to use
+the same ECs in one generation.
+
+## Detailed device specific behavior
+- On GM45 era laptops, the expected behavior is that you will run the utility
+  for the first time, which will tell the EC to set the descriptor override on
+  the next boot. Then you will need to shut down the system, after which the
+  system will automatically boot up. You should then re-run the utility to
+  disable SMM, after which you can run flashrom. Finally, you should run the
+  utility a third time to reenable SMM so that shutdown works properly
+  afterwards.
+- On 1st Generation Intel Core systems such as the E6410 and newer, run the
+  utility and shutdown in the same way as the E6400. However, it seems like the
+  EC no longer automatically boots the system. In this case you should manually
+  power it on. It also seems that the firmware does not set the BIOS Lock bit
+  when the descriptor override is set, making the 2nd run after the reboot
+  technically unnecessary. There is no harm in rerunning it though, as the
+  utility can detect when the flash is unlocked and perform the correct steps
+  as necessary.
+
+## How it works
+There are several ways the firmware can protect itself from being overwritten.
+One way is the Intel Flash Descriptor (IFD) permissions. On Intel systems, the
+flash image is divided into several regions such as the IFD itself, Gigabit
+Ethernet (GBE) non-volative memory, Management Engine (ME) firmware, Platform
+Data (PD), and the BIOS. The IFD contains a section which specifies the
+read/write permissions for each SPI controller (such as the host system) and
+each region of the flash, which are enforced by the chipset.
+
+On the Latitude E6400, the host has read-only access to the IFD, no access to
+the ME region, and read-write access to the PD, GBE, and BIOS regions. In order
+for flashrom to write to the entire flash internally, the host needs full
+permissions to all of these regions. Since the IFD is read only, we cannot
+change these permissions unless we directly access the chip using an external
+programmer, which defeats the purpose of internal flashing.
+
+However, Intel chipsets have a pin strap that allows the flash descriptor
+permissions to be overridden depending on the value of the pin at power on,
+granting RW permissions to all regions. On the ICH9M chipset on the E6400, this
+pin is HDA\_DOCK\_EN/GPIO33, which will enable the override if it is sampled
+low. This pin happens to be connected to a GPIO controlled by the Embedded
+Controller (EC), a small microcontroller on the board which handles things like
+the keyboard, touchpad, LEDs, and other system level tasks. Software can send a
+certain command to the EC, which tells it to pull GPIO33 low on the next boot.
+
+Although we now have full access according to the IFD permissions, we still
+cannot flash the whole chip, due to another protection the firmware uses.
+Before software can update the BIOS, it must change the BIOS Write Enable
+(BIOSWE) bit in the chipset from 0 to 1. However, if the BIOS Lock Enable (BLE)
+bit is also set to 1, then changing the BIOSWE bit triggers a System Management
+Interrupt (SMI). This causes the processor to enter System Management Mode
+(SMM), a highly privileged x86 execution state which operates transparently to
+the operating system. The code that SMM runs is provided by the BIOS, which
+checks the BIOSWE bit and sets it back to 0 before returning control to the OS.
+This feature is intended to only allow SMM code to update the system firmware.
+As the switch to SMM suspends the execution of the OS, it appears to the OS
+that the BIOSWE bit was never set to 1.  Unfortunately, the BLE bit cannot be
+set back to 0 once it is set to 1, so this functionality cannot be disabled
+after it is first enabled by the BIOS.
+
+Older versions of the E6400 BIOS did not set the BLE bit, allowing flashrom to
+flash the entire flash chip internally after only setting the descriptor
+override. However, more recent versions do set it, so we may have hit a dead
+end unless we force downgrade to an older version (though there is a more
+convenient method, as we are about to see).
+
+What if there was a way to sidestep the BIOS Lock entirely? As it turns out,
+there is, and it's called the Global SMI Enable (GBL\_SMI\_EN) bit. If it's set
+to 1, then the chipset will generate SMIs, such as when we change BIOSWE with
+BLE set. If it's 0, then no SMI will be generated, even with the BLE bit set.
+On the E6400, GBL\_SMI\_EN is set to 1, and it can be changed back to 0, unlike
+the BLE bit. But there still might be one bit in the way, the SMI\_LOCK bit,
+which prevents modifications to GBL\_SMI\_EN when SMI\_LOCK is 1. Like the BLE
+bit, it cannot be changed back to 0 once it set to 1. But we are in luck, as
+the vendor E6400 BIOS leaves SMI\_LOCK unset at 0, allowing us to clear
+GBL\_SMI\_EN and disable SMIs, bypassing the BIOS Lock protections.
+
+There are other possible protection mechanisms that the firmware can utilize,
+such as Protected Range Register settings, which apply access permissions to
+address ranges of the flash, similar to the IFD. However, the E6400 vendor
+firmware does not utilize these, so they will not be discussed.
diff --git a/util/dell-flash-unlock/accessors.c b/util/dell-flash-unlock/accessors.c
new file mode 100644
index 0000000..6fca281
--- /dev/null
+++ b/util/dell-flash-unlock/accessors.c
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: MIT */
+/* SPDX-FileCopyrightText: 2023 Nicholas Chin */
+
+#if defined(__linux__)
+#include <sys/io.h>
+#endif
+
+#if defined(__OpenBSD__)
+#include <machine/sysarch.h>
+#include <sys/types.h>
+#if defined(__amd64__)
+#include <amd64/pio.h>
+#elif defined(__i386__)
+#include <i386/pio.h>
+#endif /* __i386__ */
+#endif /* __OpenBSD__ */
+
+#include <errno.h>
+
+#include "accessors.h"
+
+uint32_t
+pci_read_32(uint32_t dev, uint8_t reg)
+{
+	sys_outl(PCI_CFG_ADDR, dev | reg);
+	return sys_inl(PCI_CFG_DATA);
+}
+
+void
+pci_write_32(uint32_t dev, uint8_t reg, uint32_t value)
+{
+	sys_outl(PCI_CFG_ADDR, dev | reg);
+	sys_outl(PCI_CFG_DATA, value);
+}
+
+void
+sys_outb(unsigned int port, uint8_t data)
+{
+	#if defined(__linux__)
+	outb(data, port);
+	#endif
+	#if defined(__OpenBSD__)
+	outb(port, data);
+	#endif
+}
+
+void
+sys_outl(unsigned int port, uint32_t data)
+{
+	#if defined(__linux__)
+	outl(data, port);
+	#endif
+	#if defined(__OpenBSD__)
+	outl(port, data);
+	#endif
+}
+
+uint8_t
+sys_inb(unsigned int port)
+{
+	#if defined(__linux__) || defined (__OpenBSD__)
+	return inb(port);
+	#endif
+	return 0;
+}
+
+uint32_t
+sys_inl(unsigned int port)
+{
+	#if defined(__linux__) || defined (__OpenBSD__)
+	return inl(port);
+	#endif
+	return 0;
+}
+
+int
+sys_iopl(int level)
+{
+#if defined(__linux__)
+	return iopl(level);
+#endif
+#if defined(__OpenBSD__)
+#if defined(__i386__)
+	return i386_iopl(level);
+#elif defined(__amd64__)
+	return amd64_iopl(level);
+#endif /* __amd64__ */
+#endif /* __OpenBSD__ */
+	errno = ENOSYS;
+	return -1;
+}
diff --git a/util/dell-flash-unlock/accessors.h b/util/dell-flash-unlock/accessors.h
new file mode 100644
index 0000000..a19f215
--- /dev/null
+++ b/util/dell-flash-unlock/accessors.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: MIT */
+/* SPDX-FileCopyrightText: 2023 Nicholas Chin */
+
+#include <stdint.h>
+
+#define PCI_CFG_ADDR 0xcf8
+#define PCI_CFG_DATA 0xcfc
+#define PCI_DEV(bus, dev, func) (1u << 31 | bus << 16 | dev << 11 | func << 8)
+
+uint32_t pci_read_32(uint32_t dev, uint8_t reg);
+void pci_write_32(uint32_t dev, uint8_t reg, uint32_t value);
+
+int sys_iopl(int level);
+void sys_outb(unsigned int port, uint8_t data);
+void sys_outl(unsigned int port, uint32_t data);
+uint8_t sys_inb(unsigned int port);
+uint32_t sys_inl(unsigned int port);
diff --git a/util/dell-flash-unlock/dell_flash_unlock.c b/util/dell-flash-unlock/dell_flash_unlock.c
new file mode 100644
index 0000000..174a1c9
--- /dev/null
+++ b/util/dell-flash-unlock/dell_flash_unlock.c
@@ -0,0 +1,217 @@
+/* SPDX-License-Identifier: MIT */
+/* SPDX-FileCopyrightText: 2023 Nicholas Chin */
+
+#include <sys/mman.h>
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "accessors.h"
+
+int get_fdo_status(void);
+int check_lpc_decode(void);
+void ec_set_fdo();
+void write_ec_reg(uint8_t index, uint8_t data);
+void send_ec_cmd(uint8_t cmd);
+int wait_ec(void);
+int check_bios_write_en(void);
+int set_gbl_smi_en(int enable);
+int get_gbl_smi_en(void);
+
+#define EC_INDEX 0x910
+#define EC_DATA 0x911
+#define EC_ENABLE_FDO 2
+
+#define LPC_DEV PCI_DEV(0, 0x1f, 0)
+
+#define RCBA_MMIO_LEN 0x4000
+
+/* Register offsets */
+#define SPIBAR 0x3800
+#define HSFS_REG  0x04
+#define SMI_EN_REG 0x30
+
+volatile uint8_t *rcba_mmio;
+uint16_t pmbase;
+
+int
+main(int argc, char *argv[])
+{
+	int devmemfd;
+	(void)argc;
+	(void)argv;
+
+	if (sys_iopl(3) == -1)
+		err(errno, "Could not access IO ports");
+	if ((devmemfd = open("/dev/mem", O_RDONLY)) == -1)
+		err(errno, "/dev/mem");
+
+	/* Read RCBA and PMBASE from the LPC config registers */
+	long int rcba = pci_read_32(LPC_DEV, 0xf0) & 0xffffc000;
+	pmbase = pci_read_32(LPC_DEV, 0x40) & 0xff80;
+
+	/* FDO pin-strap status bit is in RCBA mmio space */
+	rcba_mmio = mmap(0, RCBA_MMIO_LEN, PROT_READ, MAP_SHARED, devmemfd,
+			rcba);
+	if (rcba_mmio == MAP_FAILED)
+		err(errno, "Could not map RCBA");
+
+	if (get_fdo_status() == 1) { /* Descriptor not overridden */
+		if (check_lpc_decode() == -1)
+			err(errno = ECANCELED, "Can't forward I/O to LPC");
+
+		printf("Sending FDO override command to EC:\n");
+		ec_set_fdo();
+		printf("Flash Descriptor Override enabled.\n"
+			"Shut down (don't reboot) now.\n\n"
+			"The EC may auto-boot on some systems; if not then "
+			"manually power on.\n When the system boots rerun "
+			"this utility to finish unlocking.\n");
+	} else if (check_bios_write_en() == 0) {
+		/* SMI locks in place, try disabling SMIs to bypass them */
+		if (set_gbl_smi_en(0)) {
+			printf("SMIs disabled. Internal flashing should work "
+				"now.\n After flashing, re-run this utility "
+				"to enable SMIs.\n (shutdown is buggy when "
+				"SMIs are disabled)\n");
+		} else {
+			err(errno = ECANCELED, "Could not disable SMIs!");
+		}
+	} else { /* SMI locks not in place or bypassed */
+		if (get_gbl_smi_en()) {
+			/* SMIs are still enabled, assume this is an Exx10
+			 * or newer which don't need the SMM bypass */
+			printf("Flash is unlocked.\n"
+				"Internal flashing should work.\n");
+		} else {
+			/* SMIs disabled, assume this is an Exx00 after
+			 * unlocking and flashing */
+			set_gbl_smi_en(1);
+			printf("SMIs enabled.\n"
+				"You can now shutdown the system.\n");
+		}
+	}
+	return errno;
+}
+
+int
+get_fdo_status(void)
+{
+	return (*(uint16_t*)(rcba_mmio + SPIBAR + HSFS_REG) >> 13) & 1;
+}
+
+int
+check_lpc_decode(void)
+{
+	/* Check that at a Generic Decode Range Register is set up to
+	 * forward I/O ports 0x910 and 0x911 over LPC for the EC */
+	int i = 0;
+	int gen_dec_free = -1;
+	for (; i < 4; i++) {
+		uint32_t reg_val = pci_read_32(LPC_DEV, 0x84 + 4*i);
+		uint16_t base_addr = reg_val & 0xfffc;
+		uint16_t mask = ((reg_val >> 16) & 0xfffc) | 0x3;
+
+		/* Bit 0 is the enable for each decode range. If disabled, note
+		 * this register as available to add our own range decode */
+		if ((reg_val & 1) == 0)
+			gen_dec_free = i;
+
+		/* Check if the current range register matches port 0x910.
+		 * 0x911 doesn't need to be checked as the LPC bridge only
+		 * decodes at the dword level, and thus a check is redundant */
+		if ((0x910 & ~mask) == base_addr) {
+			return 0;
+		}
+	}
+
+	/* No matching range found, try setting a range in a free register */
+	if (gen_dec_free != -1) {
+		/* Set up an I/O decode range from 0x910-0x913 */
+		pci_write_32(LPC_DEV, 0x84 + 4 * gen_dec_free, 0x911);
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+void
+ec_set_fdo()
+{
+	/* EC FDO command arguments for reference:
+	 * 0 = Query EC FDO status
+	 * 2 = Enable FDO for next boot
+	 * 3 = Disable FDO for next boot */
+	write_ec_reg(0x12, EC_ENABLE_FDO);
+	send_ec_cmd(0xb8);
+}
+
+void
+write_ec_reg(uint8_t index, uint8_t data)
+{
+	sys_outb(EC_INDEX, index);
+	sys_outb(EC_DATA, data);
+}
+
+void
+send_ec_cmd(uint8_t cmd)
+{
+	sys_outb(EC_INDEX, 0);
+	sys_outb(EC_DATA, cmd);
+	if (wait_ec() == -1)
+		err(errno = ECANCELED, "Timeout while waiting for EC!");
+}
+
+int
+wait_ec(void)
+{
+	uint8_t busy;
+	int timeout = 1000;
+	do {
+		sys_outb(EC_INDEX, 0);
+		busy = sys_inb(EC_DATA);
+		timeout--;
+		usleep(1000);
+	} while (busy && timeout > 0);
+	return timeout > 0 ? 0 : -1;
+}
+
+int
+check_bios_write_en(void)
+{
+	uint8_t bios_cntl = pci_read_32(LPC_DEV, 0xdc) & 0xff;
+	/* Bit 5 = SMM BIOS Write Protect Disable (SMM_BWP)
+	 * Bit 1 = BIOS Lock Enable (BLE)
+	 * If both are 0, then there's no write protection */
+	if ((bios_cntl & 0x22) == 0)
+		return 1;
+
+	/* SMM protection is enabled, but try enabling writes
+	 * anyway in case the vendor SMM code doesn't reset it */
+	pci_write_32(LPC_DEV, 0xdc, bios_cntl | 0x1);
+	return pci_read_32(LPC_DEV, 0xdc) & 0x1;
+}
+
+int
+set_gbl_smi_en(int enable)
+{
+	uint32_t smi_en = sys_inl(pmbase + SMI_EN_REG);
+	if (enable) {
+		smi_en |= 1;
+	} else {
+		smi_en &= ~1;
+	}
+	sys_outl(pmbase + SMI_EN_REG, smi_en);
+	return (get_gbl_smi_en() == enable);
+}
+
+int
+get_gbl_smi_en(void)
+{
+	return sys_inl(pmbase + SMI_EN_REG) & 1;
+}