x86/fsgsbase/64: Convert the ELF core dump code to the new FSGSBASE helpers

Replace open-coded rdmsr()'s with their <asm/fsgsbase.h> API
counterparts.

No change in functionality intended.

[ mingo: Wrote new changelog. ]

Based-on-code-from: Andy Lutomirski <[e-mail]>
Signed-off-by: Chang S. Bae <[e-mail]>
Reviewed-by: Andi Kleen <[e-mail]>
Reviewed-by: Andy Lutomirski <[e-mail]>
Reviewed-by: Thomas Gleixner <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Markus T Metzger <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ravi Shankar <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/elf.h

···
 #include <asm/ptrace.h>
 #include <asm/user.h>
 #include <asm/auxvec.h>
+#include <asm/fsgsbase.h>
 
 typedef unsigned long elf_greg_t;
 
···
 
 #define ELF_CORE_COPY_REGS(pr_reg, regs)			\
 do {								\
-	unsigned long base;					\
 	unsigned v;						\
 	(pr_reg)[0] = (regs)->r15;				\
 	(pr_reg)[1] = (regs)->r14;				\
···
 	(pr_reg)[18] = (regs)->flags;				\
 	(pr_reg)[19] = (regs)->sp;				\
 	(pr_reg)[20] = (regs)->ss;				\
-	rdmsrl(MSR_FS_BASE, base); (pr_reg)[21] = base;		\
-	rdmsrl(MSR_KERNEL_GS_BASE, base); (pr_reg)[22] = base;	\
+	(pr_reg)[21] = x86_fsbase_read_cpu();			\
+	(pr_reg)[22] = x86_gsbase_read_cpu_inactive();		\
 	asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v;	\
 	asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v;	\
 	asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v;	\