arm64: Implement the compat_sys_call_table in C

Unlike the sys_call_table[], the compat one was implemented in sys32.S
making it impossible to notice discrepancies between the number of
compat syscalls and the __NR_compat_syscalls macro, the latter having to
be defined in asm/unistd.h as including asm/unistd32.h would cause
conflicts on __NR_* definitions. With this patch, incorrect
__NR_compat_syscalls values will result in a build-time error.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>

arch/arm64/include/asm/unistd.h

@@ -48,6 +48,9 @@
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
+
+#ifndef __COMPAT_SYSCALL_NR
 #include <uapi/asm/unistd.h>
+#endif
 
 #define NR_syscalls (__NR_syscalls)

arch/arm64/kernel/Makefile

@@ -19,7 +19,7 @@ arm64-obj-y		:= cputable.o debug-monitors.o entry.o irq.o fpsimd.o	\
 			   cpuinfo.o cpu_errata.o alternative.o cacheinfo.o
 
 arm64-obj-$(CONFIG_COMPAT)		+= sys32.o kuser32.o signal32.o 	\
-					   sys_compat.o 			\
+					   sys_compat.o entry32.o		\
 					   ../../arm/kernel/opcodes.o
 arm64-obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o entry-ftrace.o
 arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o

arch/arm64/kernel/entry.S

@@ -433,7 +433,7 @@ el0_svc_compat:
 	/*
 	 * AArch32 syscall handling
 	 */
-	adr	stbl, compat_sys_call_table	// load compat syscall table pointer
+	adrp	stbl, compat_sys_call_table	// load compat syscall table pointer
 	uxtw	scno, w7			// syscall number in w7 (r7)
 	mov     sc_nr, #__NR_compat_syscalls
 	b	el0_svc_naked

arch/arm64/kernel/sys32.S → arch/arm64/kernel/entry32.S

@@ -27,26 +27,26 @@
  * System call wrappers for the AArch32 compatibility layer.
  */
 
-compat_sys_sigreturn_wrapper:
+ENTRY(compat_sys_sigreturn_wrapper)
 	mov	x0, sp
 	mov	x27, #0		// prevent syscall restart handling (why)
 	b	compat_sys_sigreturn
 ENDPROC(compat_sys_sigreturn_wrapper)
 
-compat_sys_rt_sigreturn_wrapper:
+ENTRY(compat_sys_rt_sigreturn_wrapper)
 	mov	x0, sp
 	mov	x27, #0		// prevent syscall restart handling (why)
 	b	compat_sys_rt_sigreturn
 ENDPROC(compat_sys_rt_sigreturn_wrapper)
 
-compat_sys_statfs64_wrapper:
+ENTRY(compat_sys_statfs64_wrapper)
 	mov	w3, #84
 	cmp	w1, #88
 	csel	w1, w3, w1, eq
 	b	compat_sys_statfs64
 ENDPROC(compat_sys_statfs64_wrapper)
 
-compat_sys_fstatfs64_wrapper:
+ENTRY(compat_sys_fstatfs64_wrapper)
 	mov	w3, #84
 	cmp	w1, #88
 	csel	w1, w3, w1, eq
@@ -58,33 +58,33 @@ ENDPROC(compat_sys_fstatfs64_wrapper)
  * in registers or that take 32-bit parameters which require sign
  * extension.
  */
-compat_sys_pread64_wrapper:
+ENTRY(compat_sys_pread64_wrapper)
 	regs_to_64	x3, x4, x5
 	b	sys_pread64
 ENDPROC(compat_sys_pread64_wrapper)
 
-compat_sys_pwrite64_wrapper:
+ENTRY(compat_sys_pwrite64_wrapper)
 	regs_to_64	x3, x4, x5
 	b	sys_pwrite64
 ENDPROC(compat_sys_pwrite64_wrapper)
 
-compat_sys_truncate64_wrapper:
+ENTRY(compat_sys_truncate64_wrapper)
 	regs_to_64	x1, x2, x3
 	b	sys_truncate
 ENDPROC(compat_sys_truncate64_wrapper)
 
-compat_sys_ftruncate64_wrapper:
+ENTRY(compat_sys_ftruncate64_wrapper)
 	regs_to_64	x1, x2, x3
 	b	sys_ftruncate
 ENDPROC(compat_sys_ftruncate64_wrapper)
 
-compat_sys_readahead_wrapper:
+ENTRY(compat_sys_readahead_wrapper)
 	regs_to_64	x1, x2, x3
 	mov	w2, w4
 	b	sys_readahead
 ENDPROC(compat_sys_readahead_wrapper)
 
-compat_sys_fadvise64_64_wrapper:
+ENTRY(compat_sys_fadvise64_64_wrapper)
 	mov	w6, w1
 	regs_to_64	x1, x2, x3
 	regs_to_64	x2, x4, x5
@@ -92,24 +92,14 @@ compat_sys_fadvise64_64_wrapper:
 	b	sys_fadvise64_64
 ENDPROC(compat_sys_fadvise64_64_wrapper)
 
-compat_sys_sync_file_range2_wrapper:
+ENTRY(compat_sys_sync_file_range2_wrapper)
 	regs_to_64	x2, x2, x3
 	regs_to_64	x3, x4, x5
 	b	sys_sync_file_range2
 ENDPROC(compat_sys_sync_file_range2_wrapper)
 
-compat_sys_fallocate_wrapper:
+ENTRY(compat_sys_fallocate_wrapper)
 	regs_to_64	x2, x2, x3
 	regs_to_64	x3, x4, x5
 	b	sys_fallocate
 ENDPROC(compat_sys_fallocate_wrapper)
-
-#undef __SYSCALL
-#define __SYSCALL(x, y)		.quad	y	// x
-
-/*
- * The system calls table must be 4KB aligned.
- */
-	.align	12
-ENTRY(compat_sys_call_table)
-#include <asm/unistd32.h>

arch/arm64/kernel/sys32.c

+/*
+ * arch/arm64/kernel/sys32.c
+ *
+ * Copyright (C) 2015 ARM Ltd.
+ *
+ * This program is free software(void); you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http(void);//www.gnu.org/licenses/>.
+ */
+
+/*
+ * Needed to avoid conflicting __NR_* macros between uapi/asm/unistd.h and
+ * asm/unistd32.h.
+ */
+#define __COMPAT_SYSCALL_NR
+
+#include <linux/compiler.h>
+#include <linux/syscalls.h>
+
+asmlinkage long compat_sys_sigreturn_wrapper(void);
+asmlinkage long compat_sys_rt_sigreturn_wrapper(void);
+asmlinkage long compat_sys_statfs64_wrapper(void);
+asmlinkage long compat_sys_fstatfs64_wrapper(void);
+asmlinkage long compat_sys_pread64_wrapper(void);
+asmlinkage long compat_sys_pwrite64_wrapper(void);
+asmlinkage long compat_sys_truncate64_wrapper(void);
+asmlinkage long compat_sys_ftruncate64_wrapper(void);
+asmlinkage long compat_sys_readahead_wrapper(void);
+asmlinkage long compat_sys_fadvise64_64_wrapper(void);
+asmlinkage long compat_sys_sync_file_range2_wrapper(void);
+asmlinkage long compat_sys_fallocate_wrapper(void);
+
+#undef __SYSCALL
+#define __SYSCALL(nr, sym)	[nr] = sym,
+
+/*
+ * The sys_call_table array must be 4K aligned to be accessible from
+ * kernel/entry.S.
+ */
+void * const compat_sys_call_table[__NR_compat_syscalls] __aligned(4096) = {
+	[0 ... __NR_compat_syscalls - 1] = sys_ni_syscall,
+#include <asm/unistd32.h>
+};