On Thu, 18 May, at 02:39:30PM, Baoquan He wrote: > For EFI with 'efi=old_map' kernel option specified, Kernel will panic > when kaslr is enabled. > > The back trace is: > > BUG: unable to handle kernel paging request at 000000007febd57e > IP: 0x7febd57e > PGD 1025a067 > PUD 0 > > Oops: 0010 [#1] SMP > [ ... ] > Call Trace: > ? efi_call+0x58/0x90 > ? printk+0x58/0x6f > efi_enter_virtual_mode+0x3c5/0x50d > start_kernel+0x40f/0x4b8 > ? set_init_arg+0x55/0x55 > ? early_idt_handler_array+0x120/0x120 > x86_64_start_reservations+0x24/0x26 > x86_64_start_kernel+0x14c/0x16f > start_cpu+0x14/0x14 > > The root cause is the ident mapping is not built correctly in old_map case. > > For nokaslr kernel, PAGE_OFFSET is 0xffff880000000000 which is PGDIR_SIZE > aligned. We can borrow the pud table from direct mapping safely. Given a > physical address X, we have pud_index(X) == pud_index(__va(X)). However, > for kaslr kernel, PAGE_OFFSET is PUD_SIZE aligned. For a given physical > address X, pud_index(X) != pud_index(__va(X)). We can't only copy pgd entry > from direct mapping to build ident mapping, instead need copy pud entry > one by one from direct mapping. > > Fix it. > > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> > Signed-off-by: Dave Young <dyoung@xxxxxxxxxx> > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: Thomas Garnier <thgarnie@xxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Russ Anderson <rja@xxxxxxx> > Cc: Frank Ramsay <frank.ramsay@xxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: linux-efi@xxxxxxxxxxxxxxx > --- > v3->v4: > 1. Forget running scripts/checkpatch.pl to check patch, there are several > code stype issue. Correct them in this version. > > v2->v3: > 1. Rewrite code to copy pud entry one by one so that code can be understood > better. Usually we only have less than 1TB or several TB memory, pud entry > copy one by one won't impact efficiency. > > 2. Adding p4d page table handling. > > v1->v2: > Change code and add description according to Thomas's suggestion as below: > > 1. Add checking if pud table is allocated successfully. If not just break > the for loop. > > 2. Add code comment to explain how the 1:1 mapping is built in efi_call_phys_prolog > > 3. Other minor change > > arch/x86/platform/efi/efi_64.c | 70 +++++++++++++++++++++++++++++++++++++----- > 1 file changed, 62 insertions(+), 8 deletions(-) Thanks, applied. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
