diff options
| author | Arvind Sankar <nivedita@alum.mit.edu> | 2020-10-16 16:04:01 -0400 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2020-10-19 19:39:50 +0200 |
| commit | b17a45b6e53f6613118b2e5cfc4a992cc50deb2c (patch) | |
| tree | c377c64b30b28db018fb2686b0d144c73455e415 /arch/x86/boot/compressed/head_64.S | |
| parent | 103a4908ad4da9decdf9bc7216ec5a4861edf703 (diff) | |
x86/boot/64: Explicitly map boot_params and command line
Commits
ca0e22d4f011 ("x86/boot/compressed/64: Always switch to own page table")
8570978ea030 ("x86/boot/compressed/64: Don't pre-map memory in KASLR code")
set up a new page table in the decompressor stub, but without explicit
mappings for boot_params and the kernel command line, relying on the #PF
handler instead.
This is fragile, as boot_params and the command line mappings are
required for the main kernel. If EARLY_PRINTK and RANDOMIZE_BASE are
disabled, a QEMU/OVMF boot never accesses the command line in the
decompressor stub, and so it never gets mapped. The main kernel accesses
it from the identity mapping if AMD_MEM_ENCRYPT is enabled, and will
crash.
Fix this by adding back the explicit mapping of boot_params and the
command line.
Note: the changes also removed the explicit mapping of the main kernel,
with the result that .bss and .brk may not be in the identity mapping,
but those don't get accessed by the main kernel before it switches to
its own page tables.
[ bp: Pass boot_params with a MOV %rsp... instead of PUSH/POP. Use
block formatting for the comment. ]
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Link: https://lkml.kernel.org/r/20201016200404.1615994-1-nivedita@alum.mit.edu
Diffstat (limited to 'arch/x86/boot/compressed/head_64.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 1c80f1738fd9..017de6cc87dc 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -544,6 +544,9 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) pushq %rsi call set_sev_encryption_mask call load_stage2_idt + + /* Pass boot_params to initialize_identity_maps() */ + movq (%rsp), %rdi call initialize_identity_maps popq %rsi |