224aefd057
The EFI Boot Services can be used after ExitBootServices() call because
the GRUB code still may allocate memory.
An example call stack is:
grub_multiboot_boot
grub_multiboot2_make_mbi
grub_efi_finish_boot_services
b->exit_boot_services
normal_boot
grub_relocator32_boot
grub_relocator_alloc_chunk_align_safe
grub_relocator_alloc_chunk_align
grub_malloc
grub_memalign
grub_mm_add_region_fn
[= grub_efi_mm_add_regions]
grub_efi_allocate_any_pages
grub_efi_allocate_pages_real
b->allocate_pages
This can lead to confusing errors. After ExitBootServices() call
b->allocate_pages may point to the NULL address resulting in something like:
!!!! X64 Exception Type - 01(#DB - Debug) CPU Apic ID - 00000000 !!!!
RIP - 000000000000201F, CS - 0000000000000038, RFLAGS - 0000000000200002
RAX - 000000007F9EE010, RCX - 0000000000000001, RDX - 0000000000000002
RBX - 0000000000000006, RSP - 00000000001CFBEC, RBP - 0000000000000000
RSI - 0000000000000000, RDI - 00000000FFFFFFFF
R8 - 0000000000000006, R9 - 000000007FEDFFB8, R10 - 0000000000000000
R11 - 0000000000000475, R12 - 0000000000000001, R13 - 0000000000000002
R14 - 00000000FFFFFFFF, R15 - 000000007E432C08
DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030
GS - 0000000000000030, SS - 0000000000000030
CR0 - 0000000080010033, CR2 - 0000000000000000, CR3 - 000000007FC01000
CR4 - 0000000000000668, CR8 - 0000000000000000
DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 000000007F9DE000 0000000000000047, LDTR - 0000000000000000
IDTR - 000000007F470018 0000000000000FFF, TR - 0000000000000000
FXSAVE_STATE - 00000000001CF840
Ideally we would like to avoid all memory allocations after exiting EFI
Boot Services altogether but that requires significant code changes. This
patch adds a simple workaround that resets grub_mm_add_region_fn to NULL
after ExitBootServices() call, so:
- Memory allocations have a better chance of succeeding because grub_memalign()
will try to reclaim the disk cache if it sees a NULL in grub_mm_add_region_fn.
- At worst it will fail to allocate memory but it will explicitly tell users
that it's out of memory, which is still much better than the current
situation where it fails in a fairly random way and triggers a CPU fault.
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'