From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> 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 <dave.hansen@xxxxxxxxxxxxxxx> Cc: Moritz Lipp <moritz.lipp@xxxxxxxxxxxxxx> Cc: Daniel Gruss <daniel.gruss@xxxxxxxxxxxxxx> Cc: Michael Schwarz <michael.schwarz@xxxxxxxxxxxxxx> Cc: Richard Fellner <richard.fellner@xxxxxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: x86@xxxxxxxxxx --- 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 2017-11-22 15:45:47.913619742 -0800 +++ b/arch/x86/kernel/head_64.S 2017-11-22 15:45:47.916619742 -0800 @@ -342,11 +342,24 @@ 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 */ @@ -365,6 +378,7 @@ 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 @@ -379,6 +393,7 @@ 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 @@ -391,6 +406,7 @@ NEXT_PAGE(level2_ident_pgt) #else NEXT_PGD_PAGE(init_top_pgt) .fill 512,8,0 + .fill KAISER_USER_PGD_FILL,8,0 #endif #ifdef CONFIG_X86_5LEVEL _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
