diff options
| -rw-r--r-- | sys/boot/i386/btx/btx/btx.S | 95 |
1 files changed, 60 insertions, 35 deletions
diff --git a/sys/boot/i386/btx/btx/btx.S b/sys/boot/i386/btx/btx/btx.S index 2f917e0..e762e4b 100644 --- a/sys/boot/i386/btx/btx/btx.S +++ b/sys/boot/i386/btx/btx/btx.S @@ -36,6 +36,7 @@ /* * Fields in %eflags. */ + .set PSL_RESERVED_DEFAULT,0x00000002 .set PSL_T,0x00000100 # Trap flag .set PSL_I,0x00000200 # Interrupt enable flag .set PSL_VM,0x00020000 # Virtual 8086 mode flag @@ -455,6 +456,18 @@ intx31: pushl $-1 # Dummy int no for btx_v86 * -0x3c %fs * -0x40 %ds * -0x44 %es + * -0x48 zero %eax (hardware int only) + * -0x4c zero %ecx (hardware int only) + * -0x50 zero %edx (hardware int only) + * -0x54 zero %ebx (hardware int only) + * -0x58 zero %esp (hardware int only) + * -0x5c zero %ebp (hardware int only) + * -0x60 zero %esi (hardware int only) + * -0x64 zero %edi (hardware int only) + * -0x68 zero %gs (hardware int only) + * -0x6c zero %fs (hardware int only) + * -0x70 zero %ds (hardware int only) + * -0x74 zero %es (hardware int only) */ int_hw: cld # String ops inc pusha # Save gp regs @@ -467,12 +480,15 @@ int_hw: cld # String ops inc pushl %ds # address popl %es # data leal 0x44(%esp,1),%esi # Base of frame + movl %esp,MEM_ESPR-0x04 # Save kernel stack pointer movl -0x14(%esi),%eax # Get Int no cmpl $-1,%eax # Hardware interrupt? - jne intusr.2 # Yes + jne intusr.1 # Yes /* - * v86 calls save the btx_v86 pointer on the real mode stack and read the - * address and flags from the btx_v86 structure. + * v86 calls save the btx_v86 pointer on the real mode stack and read + * the address and flags from the btx_v86 structure. For interrupt + * handler invocations (VM86 INTx requests), disable interrupts, + * tracing, and alignment checking while the handler runs. */ movl $MEM_USR,%ebx # User base movl %ebx,%edx # address @@ -482,35 +498,36 @@ int_hw: cld # String ops inc movl %edx,MEM_ESPR-0x08 # Save btx_v86 ptr movl V86_ADDR(%edx),%eax # Get int no/address movl V86_CTL(%edx),%edx # Get control flags + movl -0x08(%esi),%ebx # Save user flags in %ebx + testl $V86F_ADDR,%edx # Segment:offset? + jnz intusr.4 # Yes + andl $~(PSL_I|PSL_T|PSL_AC),%ebx # Disable interrupts, tracing, + # and alignment checking for + # interrupt handler jmp intusr.3 # Skip hardware interrupt /* - * Hardware interrupts store a NULL btx_v86 pointer and use the address - * (interrupt number) from the stack with empty flags. Also, we clear - * the segment registers for the interrupt handler. + * Hardware interrupts store a NULL btx_v86 pointer and use the + * address (interrupt number) from the stack with empty flags. Also, + * push a dummy frame of zeros onto the stack for all the general + * purpose and segment registers and clear %eflags. This gives the + * hardware interrupt handler a clean slate. */ -intusr.2: xorl %edx,%edx # Control flags +intusr.1: xorl %edx,%edx # Control flags movl %edx,MEM_ESPR-0x08 # NULL btx_v86 ptr - movl %edx,-0x38(%esi) # Real mode %gs of 0 - movl %edx,-0x3c(%esi) # Real mode %fs of 0 - movl %edx,-0x40(%esi) # Real mode %ds of 0 - movl %edx,-0x44(%esi) # Real mode %es of 0 + movl $12,%ecx # Frame is 12 dwords +intusr.2: pushl $0x0 # Fill frame + loop intusr.2 # with zeros + movl $PSL_RESERVED_DEFAULT,%ebx # Set clean %eflags /* - * %eax now holds either the interrupt number or segment:offset of function. - * %edx now holds the V86F_* flags. - * - * For interrupt handler invocations (either hardware interrupts or VM86 - * INTx requests) we also disable interrupts, tracing, and alignment checking - * while the handler runs. + * Look up real mode IDT entry for hardware interrupts and VM86 INTx + * requests. */ -intusr.3: movl -0x08(%esi),%ebx # Save user flags in %ebx - testl $V86F_ADDR,%edx # Segment:offset? - jnz intusr.4 # Yes - shll $0x2,%eax # Scale +intusr.3: shll $0x2,%eax # Scale movl (%eax),%eax # Load int vector - andl $~(PSL_I|PSL_T|PSL_AC),%ebx # Disable interrupts, tracing, - # and alignment checking for - # interrupt handler jmp intusr.5 # Skip CALLF test +/* + * Panic if V86F_CALLF isn't set with V86F_ADDR. + */ intusr.4: testl $V86F_CALLF,%edx # Far call? jnz intusr.5 # Ok movl %edx,0x30(%esp,1) # Place VM86 flags in int no @@ -522,6 +539,11 @@ intusr.4: testl $V86F_CALLF,%edx # Far call? popl %gs popal # Restore gp regs jmp ex_noc # Panic +/* + * %eax now holds the segment:offset of the function. + * %ebx now holds the %eflags to pass to real mode. + * %edx now holds the V86F_* flags. + */ intusr.5: movw %bx,MEM_ESPR-0x12 # Pass user flags to real mode # target /* @@ -536,8 +558,7 @@ intusr.5: movw %bx,MEM_ESPR-0x12 # Pass user flags to real mode rep # from btx_v86 movsl # to kernel stack popl %esi # Restore -intusr.6: movl %esp,MEM_ESPR-0x04 # Save kernel stack pointer - movl -0x08(%esi),%ebx # Copy user flags to real +intusr.6: movl -0x08(%esi),%ebx # Copy user flags to real movl %ebx,MEM_ESPR-0x0c # mode return trampoline movl $rret_tramp,%ebx # Set return trampoline movl %ebx,MEM_ESPR-0x10 # CS:IP @@ -611,9 +632,16 @@ rret_tramp.1: xorl %ecx,%ecx # Zero movb $SEL_TSS,%cl # Set task ltr %cx # register /* - * Now we are back in protected mode. Copy the registers off of the real - * mode stack onto the kernel stack. Also, initialize all the seg regs on - * the kernel stack. + * Now we are back in protected mode. The kernel stack frame set up + * before entering real mode is still intact. For hardware interrupts, + * leave the frame unchanged. + */ + cmpl $0,MEM_ESPR-0x08 # Leave saved regs unchanged + jz rret_tramp.3 # for hardware ints +/* + * For V86 calls, copy the registers off of the real mode stack onto + * the kernel stack as we want their updated values. Also, initialize + * the segment registers on the kernel stack. * * Note that the %esp in the kernel stack after this is garbage, but popa * ignores it, so we don't have to fix it up. @@ -624,20 +652,17 @@ rret_tramp.1: xorl %ecx,%ecx # Zero movl $8,%ecx # Copy GP regs from rep # real mode stack movsl # to kernel stack - popl %esi # Restore movl $SEL_UDATA,%eax # Selector for data seg regs movl $4,%ecx # Initialize %ds, rep # %es, %fs, and stosl # %gs /* - * If this was a V86 call, copy the saved seg regs on the real mode stack - * back over to the btx_v86 structure. Also, conditionally update the saved - * eflags on the kernel stack based on the flags from the user. + * For V86 calls, copy the saved seg regs on the real mode stack back + * over to the btx_v86 structure. Also, conditionally update the + * saved eflags on the kernel stack based on the flags from the user. */ movl MEM_ESPR-0x08,%ecx # Get btx_v86 ptr - jecxz rret_tramp.3 # Skip for hardware ints leal V86_GS(%ecx),%edi # %edi => btx_v86 seg regs - pushl %esi # Save leal MEM_ESPR-0x2c,%esi # %esi => real mode seg regs xchgl %ecx,%edx # Save btx_v86 ptr movl $4,%ecx # Copy seg regs |
