x86: fix math_emu register frame access

do_device_not_available() is the handler for #NM and it declares that
it takes a unsigned long and calls math_emu(), which takes a long
argument and surprisingly expects the stack frame starting at the zero
argument would match struct math_emu_info, which isn't true regardless
of configuration in the current code.

This patch makes do_device_not_available() take struct pt_regs like
other exception handlers and initialize struct math_emu_info with
pointer to it and pass pointer to the math_emu_info to math_emulate()
like normal C functions do.  This way, unless gcc makes a copy of
struct pt_regs in do_device_not_available(), the register frame is
correctly accessed regardless of kernel configuration or compiler
used.

This doesn't fix all math_emu problems but it at least gets it
somewhat working.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 10 deletions

diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index 6729c6a31348..50fa0ec2c8a5 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -16,10 +16,6 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 
-/* This sets the pointer FPU_info to point to the argument part
-   of the stack frame of math_emulate() */
-#define SETUP_DATA_AREA(arg)    FPU_info = (struct math_emu_info *) &arg
-
 /* s is always from a cpu register, and the cpu does bounds checking
  * during register load --> no further bounds checks needed */
 #define LDT_DESCRIPTOR(s)       (((struct desc_struct *)current->mm->context.ldt)[(s) >> 3])
@@ -38,12 +34,12 @@
 #define I387                    (current->thread.xstate)
 #define FPU_info                (I387->soft.info)
 
-#define FPU_CS                  (*(unsigned short *) &(FPU_info->regs.cs))
-#define FPU_SS                  (*(unsigned short *) &(FPU_info->regs.ss))
-#define FPU_DS                  (*(unsigned short *) &(FPU_info->regs.ds))
-#define FPU_EAX                 (FPU_info->regs.ax)
-#define FPU_EFLAGS              (FPU_info->regs.flags)
-#define FPU_EIP                 (FPU_info->regs.ip)
+#define FPU_CS                  (*(unsigned short *) &(FPU_info->regs->cs))
+#define FPU_SS                  (*(unsigned short *) &(FPU_info->regs->ss))
+#define FPU_DS                  (*(unsigned short *) &(FPU_info->regs->ds))
+#define FPU_EAX                 (FPU_info->regs->ax)
+#define FPU_EFLAGS              (FPU_info->regs->flags)
+#define FPU_EIP                 (FPU_info->regs->ip)
 #define FPU_ORIG_EIP            (FPU_info->___orig_eip)
 
 #define FPU_lookahead           (I387->soft.lookahead)