[patch 4/8] Replace sensitive instructions with macros.

Jeremy Fitzhardinge
2006-08-03T00:26:51Z

[-- Attachment #1: 004-abstract-asm.patch --]
[-- Type: text/plain, Size: 5230 bytes --]

Abstract sensitive instructions in assembler code, replacing them with
macros (which currently are #defined to the native versions). We use
long names: assembler is case-insensitive, so if something goes wrong
and macros do not expand, it would assemble anyway.

Resulting object files are exactly the same as before.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>

---
arch/i386/kernel/entry.S | 38 ++++++++++++++++++++++----------------
include/asm-i386/spinlock.h | 7 +++++--
2 files changed, 27 insertions(+), 18 deletions(-)

===================================================================
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -76,8 +76,15 @@ NT_MASK = 0x00004000
NT_MASK = 0x00004000
VM_MASK = 0x00020000

+/* These are replaces for paravirtualization */
+#define DISABLE_INTERRUPTS cli
+#define ENABLE_INTERRUPTS sti
+#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
+#define INTERRUPT_RETURN iret
+#define GET_CR0_INTO_EAX movl %cr0, %eax
+
#ifdef CONFIG_PREEMPT
-#define preempt_stop cli; TRACE_IRQS_OFF
+#define preempt_stop DISABLE_INTERRUPTS; TRACE_IRQS_OFF
#else
#define preempt_stop
#define resume_kernel restore_nocheck
@@ -233,7 +240,7 @@ check_userspace:
cmpl $SEGMENT_RPL_MASK, %eax
jb resume_kernel # not returning to v8086 or userspace
ENTRY(resume_userspace)
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
movl TI_flags(%ebp), %ecx
@@ -244,7 +251,7 @@ ENTRY(resume_userspace)

#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
- cli
+ DISABLE_INTERRUPTS
cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
jnz restore_nocheck
need_resched:
@@ -272,7 +279,7 @@ sysenter_past_esp:
* No need to follow this irqs on/off section: the syscall
* disabled irqs and here we enable it straight after entry:
*/
- sti
+ ENABLE_INTERRUPTS
pushl $(__USER_DS)
CFI_ADJUST_CFA_OFFSET 4
/*CFI_REL_OFFSET ss, 0*/
@@ -317,7 +324,7 @@ 1: movl (%ebp),%ebp
jae syscall_badsys
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp)
- cli
+ DISABLE_INTERRUPTS
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testw $_TIF_ALLWORK_MASK, %cx
@@ -327,8 +334,7 @@ 1: movl (%ebp),%ebp
movl OLDESP(%esp), %ecx
xorl %ebp,%ebp
TRACE_IRQS_ON
- sti
- sysexit
+ ENABLE_INTERRUPTS_SYSEXIT
CFI_ENDPROC

@@ -353,7 +359,7 @@ syscall_call:
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp) # store the return value
syscall_exit:
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
@@ -378,11 +384,11 @@ restore_nocheck_notrace:
RESTORE_REGS
addl $4, %esp
CFI_ADJUST_CFA_OFFSET -4
-1: iret
+1: INTERRUPT_RETURN
.section .fixup,"ax"
iret_exc:
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS
pushl $0 # no error code
pushl $do_iret_error
jmp error_code
@@ -406,7 +412,7 @@ ldt_ss:
* dosemu and wine happy. */
subl $8, %esp # reserve space for switch16 pointer
CFI_ADJUST_CFA_OFFSET 8
- cli
+ DISABLE_INTERRUPTS
TRACE_IRQS_OFF
movl %esp, %eax
/* Set up the 16bit stack frame with switch32 pointer on top,
@@ -416,7 +422,7 @@ ldt_ss:
TRACE_IRQS_IRET
RESTORE_REGS
lss 20+4(%esp), %esp # switch to 16bit stack
-1: iret
+1: INTERRUPT_RETURN
.section __ex_table,"a"
.align 4
.long 1b,iret_exc
@@ -431,7 +437,7 @@ work_pending:
jz work_notifysig
work_resched:
call schedule
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
@@ -487,7 +493,7 @@ syscall_exit_work:
testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
jz work_pending
TRACE_IRQS_ON
- sti # could let do_syscall_trace() call
+ ENABLE_INTERRUPTS # could let do_syscall_trace() call
# schedule() instead
movl %esp, %eax
movl $1, %edx
@@ -666,7 +672,7 @@ ENTRY(device_not_available)
pushl $-1 # mark this as an int
CFI_ADJUST_CFA_OFFSET 4
SAVE_ALL
- movl %cr0, %eax
+ GET_CR0_INTO_EAX
testl $0x4, %eax # EM (math emulation bit)
jne device_not_available_emulate
preempt_stop
@@ -796,7 +802,7 @@ nmi_16bit_stack:
call do_nmi
RESTORE_REGS
lss 12+4(%esp), %esp # back to 16bit stack
-1: iret
+1: INTERRUPT_RETURN
CFI_ENDPROC
.section __ex_table,"a"
.align 4
===================================================================
--- a/include/asm-i386/spinlock.h
+++ b/include/asm-i386/spinlock.h
@@ -16,6 +16,9 @@
*
* (the type definitions are in asm/spinlock_types.h)
*/
+
+#define CLI_STRING "cli"
+#define STI_STRING "sti"

#define __raw_spin_is_locked(x) \
(*(volatile signed char *)(&(x)->slock) <= 0)
@@ -43,12 +46,12 @@
"2:\t" \
"testl $0x200, %1\n\t" \
"jz 4f\n\t" \
- "sti\n" \
+ STI_STRING "\n" \
"3:\t" \
"rep;nop\n\t" \
"cmpb $0, %0\n\t" \
"jle 3b\n\t" \
- "cli\n\t" \
+ CLI_STRING "\n\t" \
"jmp 1b\n" \
"4:\t" \
"rep;nop\n\t" \

--