diff options
Diffstat (limited to 'src/cpu/x86/smm')
| -rw-r--r-- | src/cpu/x86/smm/smmhandler.S | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/cpu/x86/smm/smmhandler.S b/src/cpu/x86/smm/smmhandler.S index 7b70ce9585..9cc6582ffe 100644 --- a/src/cpu/x86/smm/smmhandler.S +++ b/src/cpu/x86/smm/smmhandler.S @@ -25,6 +25,10 @@ * to 64k if we can though. */ +#include <kconfig.h> +#include <config.h> +#define LAPIC_BASE_MSR 0x1b + /* * +--------------------------------+ 0xaffff * | Save State Map Node 0 | @@ -74,8 +78,43 @@ * * All the bad magic is not all that bad after all. */ +#define SMM_START 0xa0000 +#define SMM_END 0xb0000 +#if SMM_END <= SMM_START +#error invalid SMM configuration +#endif .global smm_handler_start smm_handler_start: +#if IS_ENABLED(CONFIG_SMM_LAPIC_REMAP_MITIGATION) + /* Check if the LAPIC register block overlaps with SMM. + * This block needs to work without data accesses because they + * may be routed into the LAPIC register block. + * Code accesses, on the other hand, are never routed to LAPIC, + * which is what makes this work in the first place. + */ + mov $LAPIC_BASE_MSR, %ecx + rdmsr + and $(~0xfff), %eax + sub $(SMM_START), %eax + cmp $(SMM_END - SMM_START), %eax + ja untampered_lapic +1: + /* emit "Crash" on serial */ + mov $(CONFIG_TTYS0_BASE), %dx + mov $'C', %al + out %al, (%dx) + mov $'r', %al + out %al, (%dx) + mov $'a', %al + out %al, (%dx) + mov $'s', %al + out %al, (%dx) + mov $'h', %al + out %al, (%dx) + /* now crash for real */ + ud2 +untampered_lapic: +#endif movw $(smm_gdtptr16 - smm_handler_start + SMM_HANDLER_OFFSET), %bx data32 lgdt %cs:(%bx) |