arm64: fix !CONFIG_COMPAT build failures

Recent arm64 builds using CONFIG_ARM64_64K_PAGES are failing with:

  arch/arm64/kernel/perf_regs.c: In function ‘perf_reg_abi’:
  arch/arm64/kernel/perf_regs.c:41:2: error: implicit declaration of function ‘is_compat_thread’

  arch/arm64/kernel/perf_event.c:1398:2: error: unknown type name ‘compat_uptr_t’

This is due to some recent arm64 perf commits with compat support:

  commit 23c7d70d:
    ARM64: perf: add support for frame pointer unwinding in compat mode

  commit 2ee0d7fd:
    ARM64: perf: add support for perf registers API

Those patches make the arm64 kernel unbuildable if CONFIG_COMPAT is not
defined and CONFIG_ARM64_64K_PAGES depends on !CONFIG_COMPAT. This patch
allows the arm64 kernel to build with and without CONFIG_COMPAT.
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/perf_event.c

@@ -1386,6 +1386,7 @@ user_backtrace(struct frame_tail __user *tail,
 	return buftail.fp;
 }
 
+#ifdef CONFIG_COMPAT
 /*
  * The registers we're interested in are at the end of the variable
  * length saved register structure. The fp points at the end of this
@@ -1430,6 +1431,7 @@ compat_user_backtrace(struct compat_frame_tail __user *tail,
 
 	return (struct compat_frame_tail __user *)compat_ptr(buftail.fp) - 1;
 }
+#endif /* CONFIG_COMPAT */
 
 void perf_callchain_user(struct perf_callchain_entry *entry,
 			 struct pt_regs *regs)
@@ -1451,6 +1453,7 @@ void perf_callchain_user(struct perf_callchain_entry *entry,
 		       tail && !((unsigned long)tail & 0xf))
 			tail = user_backtrace(tail, entry);
 	} else {
+#ifdef CONFIG_COMPAT
 		/* AARCH32 compat mode */
 		struct compat_frame_tail __user *tail;
 
@@ -1459,6 +1462,7 @@ void perf_callchain_user(struct perf_callchain_entry *entry,
 		while ((entry->nr < PERF_MAX_STACK_DEPTH) &&
 			tail && !((unsigned long)tail & 0x3))
 			tail = compat_user_backtrace(tail, entry);
+#endif
 	}
 }
 

arch/arm64/kernel/perf_regs.c

@@ -2,6 +2,8 @@
 #include <linux/kernel.h>
 #include <linux/perf_event.h>
 #include <linux/bug.h>
+
+#include <asm/compat.h>
 #include <asm/perf_regs.h>
 #include <asm/ptrace.h>