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Fix brokenness introduced with the PAGING conditional variable. The value

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of %cr0 wasn't reloaded into %eax before being modified to turn protected
mode off if PAGING was not defined.  The result was that the processor did
not exit protected mode, so when it tried to jump to segment 0x0 in the
next instruction to clear the prefetch cache like one should when leaving
protected mode, it actually tried to jump to a null selector, causing a
GPF.
This commit is contained in:
John Baldwin 2000-01-27 21:06:13 +00:00
parent d3e00c127b
commit c299f41fd9
2 changed files with 6 additions and 2 deletions
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4
sys/boot/i386/btx/btx/btx.S
View file

@ -249,11 +249,11 @@ init.9: pushb $0x0 # general
#
exit: cli # Disable interrupts
movl $MEM_ESP0,%esp # Clear stack
ifdef(`PAGING',`
#
# Turn off paging.
#
movl %cr0,%eax # Get CR0
ifdef(`PAGING',`
andl $~0x80000000,%eax # Disable
movl %eax,%cr0 # paging
')
@ -800,11 +800,13 @@ intx30: cmpl $SYS_EXEC,%eax # Exec system call?
movl $MEM_USR,%eax # User base address
addl 0xc(%esp,1),%eax # Change to user
leal 0x4(%eax),%esp # stack
ifdef(`PAGING',`
movl %cr0,%eax # Turn
andl $~0x80000000,%eax # off
movl %eax,%cr0 # paging
xorl %eax,%eax # Flush
movl %eax,%cr3 # TLB
')
popl %eax # Call
call *%eax # program
intx30.1: incb %ss:btx_hdr+0x7 # Flag reboot

4
sys/boot/i386/btx/btx/btx.s
View file

@ -249,11 +249,11 @@ init.9: pushb $0x0 # general
#
exit: cli # Disable interrupts
movl $MEM_ESP0,%esp # Clear stack
ifdef(`PAGING',`
#
# Turn off paging.
#
movl %cr0,%eax # Get CR0
ifdef(`PAGING',`
andl $~0x80000000,%eax # Disable
movl %eax,%cr0 # paging
')
@ -800,11 +800,13 @@ intx30: cmpl $SYS_EXEC,%eax # Exec system call?
movl $MEM_USR,%eax # User base address
addl 0xc(%esp,1),%eax # Change to user
leal 0x4(%eax),%esp # stack
ifdef(`PAGING',`
movl %cr0,%eax # Turn
andl $~0x80000000,%eax # off
movl %eax,%cr0 # paging
xorl %eax,%eax # Flush
movl %eax,%cr3 # TLB
')
popl %eax # Call
call *%eax # program
intx30.1: incb %ss:btx_hdr+0x7 # Flag reboot