From: Dave Hansen <[email protected]> A few PGDs come out of the kernel binary instead of being allocated dynamically. Before this patch, they are all 8k-aligned, but they must also be 8k in *size*.
The original KAISER patch did not do this. It probably just lucked out that it did not trample over data after the last PGD. Signed-off-by: Dave Hansen <[email protected]> Cc: Moritz Lipp <[email protected]> Cc: Daniel Gruss <[email protected]> Cc: Michael Schwarz <[email protected]> Cc: Richard Fellner <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Kees Cook <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: [email protected] --- b/arch/x86/kernel/head_64.S | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff -puN arch/x86/kernel/head_64.S~kaiser-head_S-pgds-need-8k-too arch/x86/kernel/head_64.S --- a/arch/x86/kernel/head_64.S~kaiser-head_S-pgds-need-8k-too 2017-11-10 11:22:11.018244945 -0800 +++ b/arch/x86/kernel/head_64.S 2017-11-10 11:22:11.021244945 -0800 @@ -340,11 +340,24 @@ GLOBAL(early_recursion_flag) GLOBAL(name) #ifdef CONFIG_KAISER +/* + * Each PGD needs to be 8k long and 8k aligned. We do not + * ever go out to userspace with these, so we do not + * strictly *need* the second page, but this allows us to + * have a single set_pgd() implementation that does not + * need to worry about whether it has 4k or 8k to work + * with. + * + * This ensures PGDs are 8k long: + */ +#define KAISER_USER_PGD_FILL 512 +/* This ensures they are 8k-aligned: */ #define NEXT_PGD_PAGE(name) \ .balign 2 * PAGE_SIZE; \ GLOBAL(name) #else #define NEXT_PGD_PAGE(name) NEXT_PAGE(name) +#define KAISER_USER_PGD_FILL 0 #endif /* Automate the creation of 1 to 1 mapping pmd entries */ @@ -363,6 +376,7 @@ NEXT_PGD_PAGE(early_top_pgt) #else .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC #endif + .fill KAISER_USER_PGD_FILL,8,0 NEXT_PAGE(early_dynamic_pgts) .fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0 @@ -372,6 +386,7 @@ NEXT_PAGE(early_dynamic_pgts) #ifndef CONFIG_XEN NEXT_PGD_PAGE(init_top_pgt) .fill 512,8,0 + .fill KAISER_USER_PGD_FILL,8,0 #else NEXT_PGD_PAGE(init_top_pgt) .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC @@ -380,6 +395,7 @@ NEXT_PGD_PAGE(init_top_pgt) .org init_top_pgt + PGD_START_KERNEL*8, 0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC + .fill KAISER_USER_PGD_FILL,8,0 NEXT_PAGE(level3_ident_pgt) .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC _
