powerpc: Enable seccomp architecture tracking

To enable seccomp constant action bitmaps, we need to have a static
mapping to the audit architecture and system call table size. Add these
for powerpc.

__LITTLE_ENDIAN__ is used here instead of CONFIG_CPU_LITTLE_ENDIAN
to keep it consistent with asm/syscall.h.
Signed-off-by: YiFei Zhu <yifeifz2@illinois.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/0b64925362671cdaa26d01bfe50b3ba5e164adfd.1605101222.git.yifeifz2@illinois.edu

arch/powerpc/include/asm/seccomp.h

@@ -8,4 +8,27 @@
 
 #include <asm-generic/seccomp.h>
 
+#ifdef __LITTLE_ENDIAN__
+#define __SECCOMP_ARCH_LE		__AUDIT_ARCH_LE
+#define __SECCOMP_ARCH_LE_NAME		"le"
+#else
+#define __SECCOMP_ARCH_LE		0
+#define __SECCOMP_ARCH_LE_NAME
+#endif
+
+#ifdef CONFIG_PPC64
+# define SECCOMP_ARCH_NATIVE		(AUDIT_ARCH_PPC64 | __SECCOMP_ARCH_LE)
+# define SECCOMP_ARCH_NATIVE_NR		NR_syscalls
+# define SECCOMP_ARCH_NATIVE_NAME	"ppc64" __SECCOMP_ARCH_LE_NAME
+# ifdef CONFIG_COMPAT
+#  define SECCOMP_ARCH_COMPAT		(AUDIT_ARCH_PPC | __SECCOMP_ARCH_LE)
+#  define SECCOMP_ARCH_COMPAT_NR	NR_syscalls
+#  define SECCOMP_ARCH_COMPAT_NAME	"ppc" __SECCOMP_ARCH_LE_NAME
+# endif
+#else /* !CONFIG_PPC64 */
+# define SECCOMP_ARCH_NATIVE		(AUDIT_ARCH_PPC | __SECCOMP_ARCH_LE)
+# define SECCOMP_ARCH_NATIVE_NR		NR_syscalls
+# define SECCOMP_ARCH_NATIVE_NAME	"ppc" __SECCOMP_ARCH_LE_NAME
+#endif
+
 #endif	/* _ASM_POWERPC_SECCOMP_H */