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authorH. Peter Anvin <hpa@zytor.com>2014-05-04 10:36:22 -0700
committerH. Peter Anvin <hpa@zytor.com>2014-05-04 12:27:37 -0700
commit34273f41d57ee8d854dcd2a1d754cbb546cb548f (patch)
tree0f3fee911ac04263045d3c1557dd5ba452dc9658 /arch/x86/kernel/entry_64.S
parent197725de65477bc8509b41388157c1a2283542bb (diff)
x86, espfix: Make it possible to disable 16-bit support
Embedded systems, which may be very memory-size-sensitive, are extremely unlikely to ever encounter any 16-bit software, so make it a CONFIG_EXPERT option to turn off support for any 16-bit software whatsoever. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
-rw-r--r--arch/x86/kernel/entry_64.S8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index bffaa986cafc..da0b9bdcc32e 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1045,8 +1045,10 @@ irq_return:
* Are we returning to a stack segment from the LDT? Note: in
* 64-bit mode SS:RSP on the exception stack is always valid.
*/
+#ifdef CONFIG_X86_ESPFIX64
testb $4,(SS-RIP)(%rsp)
jnz irq_return_ldt
+#endif
irq_return_iret:
INTERRUPT_RETURN
@@ -1058,6 +1060,7 @@ ENTRY(native_iret)
_ASM_EXTABLE(native_iret, bad_iret)
#endif
+#ifdef CONFIG_X86_ESPFIX64
irq_return_ldt:
pushq_cfi %rax
pushq_cfi %rdi
@@ -1081,6 +1084,7 @@ irq_return_ldt:
movq %rax,%rsp
popq_cfi %rax
jmp irq_return_iret
+#endif
.section .fixup,"ax"
bad_iret:
@@ -1152,6 +1156,7 @@ END(common_interrupt)
* modify the stack to make it look like we just entered
* the #GP handler from user space, similar to bad_iret.
*/
+#ifdef CONFIG_X86_ESPFIX64
ALIGN
__do_double_fault:
XCPT_FRAME 1 RDI+8
@@ -1177,6 +1182,9 @@ __do_double_fault:
retq
CFI_ENDPROC
END(__do_double_fault)
+#else
+# define __do_double_fault do_double_fault
+#endif
/*
* End of kprobes section