From: Ming Wang <wangming01@loongson.cn> mainline inclusion from mainline-v6.16-rc4 commit 39503fc84b4ea94f2bedca481de5e225e0df729d category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/ICOFL4 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The EFI memory map at 'boot_memmap' is crucial for kdump to understand the primary kernel's memory layout. This memory region, typically part of EFI Boot Services (BS) data, can be overwritten after ExitBootServices if not explicitly preserved by the kernel. This commit addresses this by: 1. Calling memblock_reserve() to reserve the entire physical region occupied by the EFI memory map (header + descriptors). This prevents the primary kernel from reallocating and corrupting this area. 2. Setting the EFI_PRESERVE_BS_REGIONS flag in efi.flags. This indicates that efforts have been made to preserve critical BS code/data regions which can be useful for other kernel subsystems or debugging. These changes ensure the original EFI memory map data remains intact, improving kdump reliability and potentially aiding other EFI-related functionalities that might rely on preserved BS code/data. Change-Id: Ibc9a7c2ffed09447ae63269e0c1e2a75d48b5a03 Signed-off-by: Ming Wang <wangming01@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn> --- arch/loongarch/kernel/efi.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/loongarch/kernel/efi.c b/arch/loongarch/kernel/efi.c index 459583c985be..76845a225e97 100644 --- a/arch/loongarch/kernel/efi.c +++ b/arch/loongarch/kernel/efi.c @@ -328,6 +328,18 @@ void __init efi_init(void) if (efi_memmap_init_early(&data) < 0) panic("Unable to map EFI memory map.\n"); + /* + * Reserve the physical memory region occupied by the EFI + * memory map table (header + descriptors). This is crucial + * for kdump, as the kdump kernel relies on this original + * memmap passed by the bootloader. Without reservation, + * this region could be overwritten by the primary kernel. + * Also, set the EFI_PRESERVE_BS_REGIONS flag to indicate that + * critical boot services data regions like this are preserved. + */ + memblock_reserve((phys_addr_t)boot_memmap, sizeof(*tbl) + data.size); + set_bit(EFI_PRESERVE_BS_REGIONS, &efi.flags); + early_memunmap(tbl, sizeof(*tbl)); } } -- 2.33.0