svn commit: r189312 - stable/4/sys/boot/i386/btx/btx
John Baldwin
jhb at FreeBSD.org
Tue Mar 3 09:16:28 PST 2009
Author: jhb
Date: Tue Mar 3 17:16:26 2009
New Revision: 189312
URL: http://svn.freebsd.org/changeset/base/189312
Log:
MFC: Use a clean slate of register state when executing hardware interrupt
handlers to avoid leaking values into the upper 16-bits of general purpose
registers when executing these routines.
Modified:
stable/4/sys/boot/i386/btx/btx/btx.s
Modified: stable/4/sys/boot/i386/btx/btx/btx.s
==============================================================================
--- stable/4/sys/boot/i386/btx/btx/btx.s Tue Mar 3 17:15:05 2009 (r189311)
+++ stable/4/sys/boot/i386/btx/btx/btx.s Tue Mar 3 17:16:26 2009 (r189312)
@@ -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
@@ -452,6 +453,18 @@ intx31: pushl $-1 # Dummy int no for
# -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
@@ -464,12 +477,15 @@ 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
@@ -479,35 +495,36 @@ 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
@@ -519,6 +536,11 @@ intusr.4: testl $V86F_CALLF,%edx # Far
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
#
@@ -533,8 +555,7 @@ intusr.5: movw %bx,MEM_ESPR-0x12 # Pass
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
@@ -608,9 +629,16 @@ 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.
@@ -621,20 +649,17 @@ 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
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