diff options
| author | Stefan Reinauer <reinauer@chromium.org> | 2011-06-01 14:01:46 -0700 |
|---|---|---|
| committer | Stefan Reinauer <stefan.reinauer@coreboot.org> | 2011-10-13 20:02:46 +0200 |
| commit | 71496bea9b84b0d4c0d3576932d72f92b4c6881a (patch) | |
| tree | 63dd80e689fadb270bce7cd796fbf9f7c09c5016 | |
| parent | d17fe51d9a9402dfdc1b6b633e52a7bf8e757949 (diff) | |
Load an IDT with NULL limit
Load an IDT with NULL limit to prevent the 16bit IDT being used
in protected mode before c_start.S sets up a 32bit IDT when entering
ram stage.
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Change-Id: I8d048c894c863ac4971fcef8f065be6b899e1d3e
Reviewed-on: http://review.coreboot.org/259
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>
| -rw-r--r-- | src/cpu/x86/16bit/entry16.inc | 15 | ||||
| -rw-r--r-- | src/cpu/x86/16bit/entry16.lds | 1 |
2 files changed, 15 insertions, 1 deletions
diff --git a/src/cpu/x86/16bit/entry16.inc b/src/cpu/x86/16bit/entry16.inc index 1eb92c82d1..9f4c0e38da 100644 --- a/src/cpu/x86/16bit/entry16.inc +++ b/src/cpu/x86/16bit/entry16.inc @@ -45,7 +45,6 @@ _start: xorl %eax, %eax movl %eax, %cr3 /* Invalidate TLB*/ - /* Invalidating the cache here seems to be a bad idea on * modern processors. Don't. * If we are hyperthreaded or we have multiple cores it is bad, @@ -55,6 +54,13 @@ _start: * entry16.inc. */ + /* Load an IDT with NULL limit to prevent the 16bit IDT being used + * in protected mode before c_start.S sets up a 32bit IDT when entering + * ram stage. + */ + movw $nullidt_offset, %bx + lidt %cs:(%bx) + /* Note: gas handles memory addresses in 16 bit code very poorly. * In particular it doesn't appear to have a directive allowing you * associate a section or even an absolute offset with a segment register. @@ -118,6 +124,13 @@ gdtptr16: .word gdt_end - gdt -1 /* compute the table limit */ .long gdt /* we know the offset */ +.align 4 +.globl nullidt +nullidt: + .word 0 /* limit */ + .long 0 + .word 0 + .globl _estart _estart: .code32 diff --git a/src/cpu/x86/16bit/entry16.lds b/src/cpu/x86/16bit/entry16.lds index 0580f0e803..112d429953 100644 --- a/src/cpu/x86/16bit/entry16.lds +++ b/src/cpu/x86/16bit/entry16.lds @@ -1 +1,2 @@ gdtptr16_offset = gdtptr16 & 0xffff; + nullidt_offset = nullidt & 0xffff; |