Messages in this thread Patch in this message | | | From | Hans-Gert Dahmen <> | Subject | [PATCH] firmware: export x86_64 platform flash bios region via sysfs | Date | Tue, 22 Jun 2021 16:23:34 +0200 |
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Make the 16MiB long memory-mapped BIOS region of the platform SPI flash on X86_64 system available via /sys/kernel/firmware/flash_mmap/bios_region for pen-testing, security analysis and malware detection on kernels which restrict module loading and/or access to /dev/mem.
It will be used by the open source Converged Security Suite. https://github.com/9elements/converged-security-suite
Signed-off-by: Hans-Gert Dahmen <hans-gert.dahmen@immu.ne> --- drivers/firmware/Kconfig | 9 ++++ drivers/firmware/Makefile | 1 + drivers/firmware/x86_64_flash_mmap.c | 65 ++++++++++++++++++++++++++++ 3 files changed, 75 insertions(+) create mode 100644 drivers/firmware/x86_64_flash_mmap.c
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig index db0ea2d2d75a..bd77ca2b4fa6 100644 --- a/drivers/firmware/Kconfig +++ b/drivers/firmware/Kconfig @@ -296,6 +296,15 @@ config TURRIS_MOX_RWTM other manufacturing data and also utilize the Entropy Bit Generator for hardware random number generation. +config X86_64_FLASH_MMAP + tristate "Export platform flash memory-mapped BIOS region" + depends on X86_64 + help + Export the memory-mapped BIOS region of the platform SPI flash as + a read-only sysfs binary attribute on X86_64 systems. The first 16MiB + will be accessible via /sys/kernel/firmware/flash_mmap/bios_region + for security and malware analysis for example. + source "drivers/firmware/broadcom/Kconfig" source "drivers/firmware/google/Kconfig" source "drivers/firmware/efi/Kconfig" diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile index 5e013b6a3692..eb7483c5a2ac 100644 --- a/drivers/firmware/Makefile +++ b/drivers/firmware/Makefile @@ -21,6 +21,7 @@ obj-$(CONFIG_QCOM_SCM) += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o obj-$(CONFIG_TI_SCI_PROTOCOL) += ti_sci.o obj-$(CONFIG_TRUSTED_FOUNDATIONS) += trusted_foundations.o obj-$(CONFIG_TURRIS_MOX_RWTM) += turris-mox-rwtm.o +obj-$(CONFIG_X86_64_FLASH_MMAP) += x86_64_flash_mmap.o obj-y += arm_scmi/ obj-y += broadcom/ diff --git a/drivers/firmware/x86_64_flash_mmap.c b/drivers/firmware/x86_64_flash_mmap.c new file mode 100644 index 000000000000..f9d871a8b516 --- /dev/null +++ b/drivers/firmware/x86_64_flash_mmap.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Export the memory-mapped BIOS region of the platform SPI flash as + * a read-only sysfs binary attribute on X86_64 systems. + * + * Copyright © 2021 immune GmbH + */ + +#include <linux/version.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/io.h> +#include <linux/sysfs.h> +#include <linux/kobject.h> + +#define FLASH_REGION_START 0xFF000000ULL +#define FLASH_REGION_SIZE 0x1000000ULL +#define FLASH_REGION_MASK (FLASH_REGION_SIZE - 1) + +struct kobject *kobj_ref; + +static ssize_t bios_region_read(struct file *file, struct kobject *kobj, + struct bin_attribute *bin_attr, char *buffer, + loff_t offset, size_t count) +{ + resource_size_t pa = FLASH_REGION_START + (offset & FLASH_REGION_MASK); + void __iomem *va = ioremap(pa, PAGE_SIZE); + + memcpy_fromio(buffer, va, PAGE_SIZE); + iounmap(va); + + return min(count, PAGE_SIZE); +} + +BIN_ATTR_RO(bios_region, FLASH_REGION_SIZE); + +static int __init flash_mmap_init(void) +{ + int ret = 0; + + kobj_ref = kobject_create_and_add("flash_mmap", firmware_kobj); + ret = sysfs_create_bin_file(kobj_ref, &bin_attr_bios_region); + if (ret) { + pr_err("sysfs_create_bin_file failed\n"); + goto error; + } + + return ret; + +error: + kobject_put(kobj_ref); + return ret; +} + +static void __exit flash_mmap_exit(void) +{ + sysfs_remove_bin_file(kernel_kobj, &bin_attr_bios_region); + kobject_put(kobj_ref); +} + +module_init(flash_mmap_init); +module_exit(flash_mmap_exit); +MODULE_DESCRIPTION("Export SPI platform flash memory mapped region via sysfs"); +MODULE_AUTHOR("Hans-Gert Dahmen <hans-gert.dahmen@immu.ne>"); +MODULE_LICENSE("GPL"); -- 2.30.2
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