diff options
| author | jhb <jhb@FreeBSD.org> | 2001-03-21 20:08:07 +0000 |
|---|---|---|
| committer | jhb <jhb@FreeBSD.org> | 2001-03-21 20:08:07 +0000 |
| commit | 5d5fc406d7ed3e2ee9afa1bb9d4a25100a3edd5d (patch) | |
| tree | 5180a8cd4eec2ca7318f713979daadfe9f47d850 /sys/boot/i386 | |
| parent | 7069cc87ccc9884a8ddbd4289fc107db4a433bfb (diff) | |
| download | FreeBSD-src-5d5fc406d7ed3e2ee9afa1bb9d4a25100a3edd5d.zip FreeBSD-src-5d5fc406d7ed3e2ee9afa1bb9d4a25100a3edd5d.tar.gz | |
Always disable paging when exiting back to real mode after receiving a
fatal trap. Also, reload the GDT register to point to BTX's GDT before
playing around with the segment registers to return to real mode. This is
helpful if the kernel causes a fatal exception before it has setup its own
IDT and fault handlers. For example, if one happens to break mtx_init().
Without these changes BTX would recursively page fault (if paging was not
disabled) or triple fault and reset the CPU (without the GDT reload)
instead of providing a potentially useful register dump.
Reviewed by: rnordier
Diffstat (limited to 'sys/boot/i386')
| -rw-r--r-- | sys/boot/i386/btx/btx/btx.S | 8 | ||||
| -rw-r--r-- | sys/boot/i386/btx/btx/btx.s | 8 |
2 files changed, 8 insertions, 8 deletions
diff --git a/sys/boot/i386/btx/btx/btx.S b/sys/boot/i386/btx/btx/btx.S index 72ba555..334bea6 100644 --- a/sys/boot/i386/btx/btx/btx.S +++ b/sys/boot/i386/btx/btx/btx.S @@ -255,14 +255,14 @@ exit: cli # Disable interrupts # Turn off paging. # movl %cr0,%eax # Get CR0 -ifdef(`PAGING',` andl $~0x80000000,%eax # Disable movl %eax,%cr0 # paging -') xorl %ecx,%ecx # Zero -ifdef(`PAGING',` movl %ecx,%cr3 # Flush TLB -') +# +# Restore the GDT in case we caught a kernel trap. +# + lgdt gdtdesc # Set GDT # # To 16 bits. # diff --git a/sys/boot/i386/btx/btx/btx.s b/sys/boot/i386/btx/btx/btx.s index 72ba555..334bea6 100644 --- a/sys/boot/i386/btx/btx/btx.s +++ b/sys/boot/i386/btx/btx/btx.s @@ -255,14 +255,14 @@ exit: cli # Disable interrupts # Turn off paging. # movl %cr0,%eax # Get CR0 -ifdef(`PAGING',` andl $~0x80000000,%eax # Disable movl %eax,%cr0 # paging -') xorl %ecx,%ecx # Zero -ifdef(`PAGING',` movl %ecx,%cr3 # Flush TLB -') +# +# Restore the GDT in case we caught a kernel trap. +# + lgdt gdtdesc # Set GDT # # To 16 bits. # |
