diff options
Diffstat (limited to 'src/cpu/x86')
| -rw-r--r-- | src/cpu/x86/smm/smm_stub.S | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/cpu/x86/smm/smm_stub.S b/src/cpu/x86/smm/smm_stub.S index c83839cc01..02532a4d9f 100644 --- a/src/cpu/x86/smm/smm_stub.S +++ b/src/cpu/x86/smm/smm_stub.S @@ -45,10 +45,49 @@ fallback_stack_top: (CR0_CD | CR0_NW | CR0_PG | CR0_AM | CR0_WP | \ CR0_NE | CR0_TS | CR0_EM | CR0_MP) +#define SMM_DEFAULT_SIZE 0x10000 + .text .code16 .global _start _start: +smm_handler_start: +#if CONFIG(SMM_LAPIC_REMAP_MITIGATION) + /* Check if the LAPIC register block overlaps with the stub. + * 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 + call 1f + /* Get the current program counter */ +1: + pop %ebx + sub %ebx, %eax + cmp $(SMM_DEFAULT_SIZE), %eax + ja untampered_lapic +1: +#if CONFIG(CONSOLE_SERIAL) + /* 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) +#endif /* CONFIG_CONSOLE_SERIAL */ + /* now crash for real */ + ud2 +untampered_lapic: +#endif movl $(smm_relocate_gdt), %ebx lgdtl (%ebx) |