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| author | jhb <jhb@FreeBSD.org> | 2013-10-15 21:08:37 +0000 |
|---|---|---|
| committer | jhb <jhb@FreeBSD.org> | 2013-10-15 21:08:37 +0000 |
| commit | 9f3020013a19321c4f393376c9191ac458efee60 (patch) | |
| tree | b6110881fed6270d389e342e12fa043e5e71428f /sys/boot/i386/btx | |
| parent | e8958f2a0be4044af0aee3bb93c99a2d92d32d22 (diff) | |
| download | FreeBSD-src-9f3020013a19321c4f393376c9191ac458efee60.zip FreeBSD-src-9f3020013a19321c4f393376c9191ac458efee60.tar.gz | |
MFC 256293:
Sanitize the %eflags returned by BIOS routines. Some BIOS routines enter
protected mode and may leave protected-mode-specific flags like PSL_NT set
when they return to real mode. This can cause a fault when BTX re-enters
protected mode after the BIOS mode returns.
Approved by: re (gjb)
Diffstat (limited to 'sys/boot/i386/btx')
| -rw-r--r-- | sys/boot/i386/btx/btx/btx.S | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/sys/boot/i386/btx/btx/btx.S b/sys/boot/i386/btx/btx/btx.S index ef3d0c7..87d09a5 100644 --- a/sys/boot/i386/btx/btx/btx.S +++ b/sys/boot/i386/btx/btx/btx.S @@ -41,6 +41,8 @@ .set PSL_RESERVED_DEFAULT,0x00000002 .set PSL_T,0x00000100 # Trap flag .set PSL_I,0x00000200 # Interrupt enable flag + .set PSL_D,0x00000400 # String instruction direction + .set PSL_NT,0x00004000 # Nested task flag .set PSL_VM,0x00020000 # Virtual 8086 mode flag .set PSL_AC,0x00040000 # Alignment check flag /* @@ -611,8 +613,8 @@ rret_tramp: movw $MEM_ESPR-0x08,%sp # Reset stack pointer pushl %ds # regs pushl %es pushfl # Save %eflags - cli # Disable interrupts - std # String ops dec + pushl $PSL_RESERVED_DEFAULT|PSL_D # Use clean %eflags with + popfl # string ops dec xorw %ax,%ax # Reset seg movw %ax,%ds # regs movw %ax,%es # (%ss is already 0) @@ -675,6 +677,7 @@ rret_tramp.1: xorl %ecx,%ecx # Zero testl $V86F_FLAGS,%edx # User wants flags? jz rret_tramp.3 # No movl MEM_ESPR-0x3c,%eax # Read real mode flags + andl $~(PSL_T|PSL_NT),%eax # Clear unsafe flags movw %ax,-0x08(%esi) # Update user flags (low 16) /* * Return to the user task |
