From 41cd96fa149b29684ebd38759fefb07f9c7d5276 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 29 Oct 2019 18:37:53 +0100 Subject: efi: libstub/arm: Account for firmware reserved memory at the base of RAM The EFI stubloader for ARM starts out by allocating a 32 MB window at the base of RAM, in order to ensure that the decompressor (which blindly copies the uncompressed kernel into that window) does not overwrite other allocations that are made while running in the context of the EFI firmware. In some cases, (e.g., U-Boot running on the Raspberry Pi 2), this is causing boot failures because this initial allocation conflicts with a page of reserved memory at the base of RAM that contains the SMP spin tables and other pieces of firmware data and which was put there by the bootloader under the assumption that the TEXT_OFFSET window right below the kernel is only used partially during early boot, and will be left alone once the memory reservations are processed and taken into account. So let's permit reserved memory regions to exist in the region starting at the base of RAM, and ending at TEXT_OFFSET - 5 * PAGE_SIZE, which is the window below the kernel that is not touched by the early boot code. Tested-by: Guillaume Gardet Signed-off-by: Ard Biesheuvel Acked-by: Chester Lin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Link: https://lkml.kernel.org/r/20191029173755.27149-5-ardb@kernel.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/libstub/arm32-stub.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'drivers/firmware/efi/libstub/arm32-stub.c') diff --git a/drivers/firmware/efi/libstub/arm32-stub.c b/drivers/firmware/efi/libstub/arm32-stub.c index e8f7aefb6813..ffa242ad0a82 100644 --- a/drivers/firmware/efi/libstub/arm32-stub.c +++ b/drivers/firmware/efi/libstub/arm32-stub.c @@ -195,6 +195,7 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table, unsigned long dram_base, efi_loaded_image_t *image) { + unsigned long kernel_base; efi_status_t status; /* @@ -204,9 +205,18 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table, * loaded. These assumptions are made by the decompressor, * before any memory map is available. */ - dram_base = round_up(dram_base, SZ_128M); + kernel_base = round_up(dram_base, SZ_128M); - status = reserve_kernel_base(sys_table, dram_base, reserve_addr, + /* + * Note that some platforms (notably, the Raspberry Pi 2) put + * spin-tables and other pieces of firmware at the base of RAM, + * abusing the fact that the window of TEXT_OFFSET bytes at the + * base of the kernel image is only partially used at the moment. + * (Up to 5 pages are used for the swapper page tables) + */ + kernel_base += TEXT_OFFSET - 5 * PAGE_SIZE; + + status = reserve_kernel_base(sys_table, kernel_base, reserve_addr, reserve_size); if (status != EFI_SUCCESS) { pr_efi_err(sys_table, "Unable to allocate memory for uncompressed kernel.\n"); @@ -220,7 +230,7 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table, *image_size = image->image_size; status = efi_relocate_kernel(sys_table, image_addr, *image_size, *image_size, - dram_base + MAX_UNCOMP_KERNEL_SIZE, 0); + kernel_base + MAX_UNCOMP_KERNEL_SIZE, 0); if (status != EFI_SUCCESS) { pr_efi_err(sys_table, "Failed to relocate kernel.\n"); efi_free(sys_table, *reserve_size, *reserve_addr); -- cgit v1.2.3-59-g8ed1b From 220dd7699c46d5940115bd797b01b2ab047c87b8 Mon Sep 17 00:00:00 2001 From: Kairui Song Date: Tue, 29 Oct 2019 18:37:54 +0100 Subject: x86, efi: Never relocate kernel below lowest acceptable address Currently, kernel fails to boot on some HyperV VMs when using EFI. And it's a potential issue on all x86 platforms. It's caused by broken kernel relocation on EFI systems, when below three conditions are met: 1. Kernel image is not loaded to the default address (LOAD_PHYSICAL_ADDR) by the loader. 2. There isn't enough room to contain the kernel, starting from the default load address (eg. something else occupied part the region). 3. In the memmap provided by EFI firmware, there is a memory region starts below LOAD_PHYSICAL_ADDR, and suitable for containing the kernel. EFI stub will perform a kernel relocation when condition 1 is met. But due to condition 2, EFI stub can't relocate kernel to the preferred address, so it fallback to ask EFI firmware to alloc lowest usable memory region, got the low region mentioned in condition 3, and relocated kernel there. It's incorrect to relocate the kernel below LOAD_PHYSICAL_ADDR. This is the lowest acceptable kernel relocation address. The first thing goes wrong is in arch/x86/boot/compressed/head_64.S. Kernel decompression will force use LOAD_PHYSICAL_ADDR as the output address if kernel is located below it. Then the relocation before decompression, which move kernel to the end of the decompression buffer, will overwrite other memory region, as there is no enough memory there. To fix it, just don't let EFI stub relocate the kernel to any address lower than lowest acceptable address. [ ardb: introduce efi_low_alloc_above() to reduce the scope of the change ] Signed-off-by: Kairui Song Signed-off-by: Ard Biesheuvel Acked-by: Jarkko Sakkinen Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Link: https://lkml.kernel.org/r/20191029173755.27149-6-ardb@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/boot/compressed/eboot.c | 4 +++- drivers/firmware/efi/libstub/arm32-stub.c | 2 +- drivers/firmware/efi/libstub/efi-stub-helper.c | 24 ++++++++++-------------- include/linux/efi.h | 18 ++++++++++++++++-- 4 files changed, 30 insertions(+), 18 deletions(-) (limited to 'drivers/firmware/efi/libstub/arm32-stub.c') diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index d6662fdef300..82bc60c8acb2 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -13,6 +13,7 @@ #include #include #include +#include #include "../string.h" #include "eboot.h" @@ -813,7 +814,8 @@ efi_main(struct efi_config *c, struct boot_params *boot_params) status = efi_relocate_kernel(sys_table, &bzimage_addr, hdr->init_size, hdr->init_size, hdr->pref_address, - hdr->kernel_alignment); + hdr->kernel_alignment, + LOAD_PHYSICAL_ADDR); if (status != EFI_SUCCESS) { efi_printk(sys_table, "efi_relocate_kernel() failed!\n"); goto fail; diff --git a/drivers/firmware/efi/libstub/arm32-stub.c b/drivers/firmware/efi/libstub/arm32-stub.c index ffa242ad0a82..41213bf5fcf5 100644 --- a/drivers/firmware/efi/libstub/arm32-stub.c +++ b/drivers/firmware/efi/libstub/arm32-stub.c @@ -230,7 +230,7 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table, *image_size = image->image_size; status = efi_relocate_kernel(sys_table, image_addr, *image_size, *image_size, - kernel_base + MAX_UNCOMP_KERNEL_SIZE, 0); + kernel_base + MAX_UNCOMP_KERNEL_SIZE, 0, 0); if (status != EFI_SUCCESS) { pr_efi_err(sys_table, "Failed to relocate kernel.\n"); efi_free(sys_table, *reserve_size, *reserve_addr); diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c index 3caae7f2cf56..35dbc2791c97 100644 --- a/drivers/firmware/efi/libstub/efi-stub-helper.c +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c @@ -260,11 +260,11 @@ fail: } /* - * Allocate at the lowest possible address. + * Allocate at the lowest possible address that is not below 'min'. */ -efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg, - unsigned long size, unsigned long align, - unsigned long *addr) +efi_status_t efi_low_alloc_above(efi_system_table_t *sys_table_arg, + unsigned long size, unsigned long align, + unsigned long *addr, unsigned long min) { unsigned long map_size, desc_size, buff_size; efi_memory_desc_t *map; @@ -311,13 +311,8 @@ efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg, start = desc->phys_addr; end = start + desc->num_pages * EFI_PAGE_SIZE; - /* - * Don't allocate at 0x0. It will confuse code that - * checks pointers against NULL. Skip the first 8 - * bytes so we start at a nice even number. - */ - if (start == 0x0) - start += 8; + if (start < min) + start = min; start = round_up(start, align); if ((start + size) > end) @@ -698,7 +693,8 @@ efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg, unsigned long image_size, unsigned long alloc_size, unsigned long preferred_addr, - unsigned long alignment) + unsigned long alignment, + unsigned long min_addr) { unsigned long cur_image_addr; unsigned long new_addr = 0; @@ -731,8 +727,8 @@ efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg, * possible. */ if (status != EFI_SUCCESS) { - status = efi_low_alloc(sys_table_arg, alloc_size, alignment, - &new_addr); + status = efi_low_alloc_above(sys_table_arg, alloc_size, + alignment, &new_addr, min_addr); } if (status != EFI_SUCCESS) { pr_efi_err(sys_table_arg, "Failed to allocate usable memory for kernel.\n"); diff --git a/include/linux/efi.h b/include/linux/efi.h index bd3837022307..d87acf62958e 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1579,9 +1579,22 @@ char *efi_convert_cmdline(efi_system_table_t *sys_table_arg, efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg, struct efi_boot_memmap *map); +efi_status_t efi_low_alloc_above(efi_system_table_t *sys_table_arg, + unsigned long size, unsigned long align, + unsigned long *addr, unsigned long min); + +static inline efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg, unsigned long size, unsigned long align, - unsigned long *addr); + unsigned long *addr) +{ + /* + * Don't allocate at 0x0. It will confuse code that + * checks pointers against NULL. Skip the first 8 + * bytes so we start at a nice even number. + */ + return efi_low_alloc_above(sys_table_arg, size, align, addr, 0x8); +} efi_status_t efi_high_alloc(efi_system_table_t *sys_table_arg, unsigned long size, unsigned long align, @@ -1592,7 +1605,8 @@ efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg, unsigned long image_size, unsigned long alloc_size, unsigned long preferred_addr, - unsigned long alignment); + unsigned long alignment, + unsigned long min_addr); efi_status_t handle_cmdline_files(efi_system_table_t *sys_table_arg, efi_loaded_image_t *image, -- cgit v1.2.3-59-g8ed1b