audit: Add generic compat syscall support

lib/audit.c provides a generic function for auditing system calls.
This patch extends it for compat syscall support on bi-architectures
(32/64-bit) by adding lib/compat_audit.c.
What is required to support this feature are:
* add asm/unistd32.h for compat system call names
* select CONFIG_AUDIT_ARCH_COMPAT_GENERIC

Signed-off-by: AKASHI Takahiro <[e-mail]>
Acked-by: Richard Guy Briggs <[e-mail]>
Signed-off-by: Eric Paris <[e-mail]>

include/linux/audit.h

···
 extern int __init audit_register_class(int class, unsigned *list);
 extern int audit_classify_syscall(int abi, unsigned syscall);
 extern int audit_classify_arch(int arch);
+/* only for compat system calls */
+extern unsigned compat_write_class[];
+extern unsigned compat_read_class[];
+extern unsigned compat_dir_class[];
+extern unsigned compat_chattr_class[];
+extern unsigned compat_signal_class[];
+
+extern int __weak audit_classify_compat_syscall(int abi, unsigned syscall);
 
 /* audit_names->type values */
 #define	AUDIT_TYPE_UNKNOWN	0	/* we don't know yet */

include/uapi/linux/audit.h

···
 #define AUDIT_ARCH_SPARC64	(EM_SPARCV9|__AUDIT_ARCH_64BIT)
 #define AUDIT_ARCH_X86_64	(EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
 
+#ifdef CONFIG_COMPAT
+#define audit_is_compat(arch)	(!((arch) & __AUDIT_ARCH_64BIT))
+#else
+#define audit_is_compat(arch)	false
+#endif
+
 #define AUDIT_PERM_EXEC		1
 #define AUDIT_PERM_WRITE	2
 #define AUDIT_PERM_READ		4

lib/Kconfig

···
 	depends on AUDIT && !AUDIT_ARCH
 	default y
 
+config AUDIT_ARCH_COMPAT_GENERIC
+	bool
+	default n
+
+config AUDIT_COMPAT_GENERIC
+	bool
+	depends on AUDIT_GENERIC && AUDIT_ARCH_COMPAT_GENERIC && COMPAT
+	default y
+
 config RANDOM32_SELFTEST
 	bool "PRNG perform self test on init"
 	default n

lib/Makefile

···
 obj-$(CONFIG_TEXTSEARCH_FSM) += ts_fsm.o
 obj-$(CONFIG_SMP) += percpu_counter.o
 obj-$(CONFIG_AUDIT_GENERIC) += audit.o
+obj-$(CONFIG_AUDIT_COMPAT_GENERIC) += compat_audit.o
 
 obj-$(CONFIG_SWIOTLB) += swiotlb.o
 obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o

lib/audit.c

···
 
 int audit_classify_arch(int arch)
 {
-	return 0;
+	if (audit_is_compat(arch))
+		return 1;
+	else
+		return 0;
 }
 
 int audit_classify_syscall(int abi, unsigned syscall)
 {
+	if (audit_is_compat(abi))
+		return audit_classify_compat_syscall(abi, syscall);
+
 	switch(syscall) {
 #ifdef __NR_open
 	case __NR_open:
···
 
 static int __init audit_classes_init(void)
 {
+#ifdef CONFIG_AUDIT_COMPAT_GENERIC
+	audit_register_class(AUDIT_CLASS_WRITE_32, compat_write_class);
+	audit_register_class(AUDIT_CLASS_READ_32, compat_read_class);
+	audit_register_class(AUDIT_CLASS_DIR_WRITE_32, compat_dir_class);
+	audit_register_class(AUDIT_CLASS_CHATTR_32, compat_chattr_class);
+	audit_register_class(AUDIT_CLASS_SIGNAL_32, compat_signal_class);
+#endif
 	audit_register_class(AUDIT_CLASS_WRITE, write_class);
 	audit_register_class(AUDIT_CLASS_READ, read_class);
 	audit_register_class(AUDIT_CLASS_DIR_WRITE, dir_class);

lib/compat_audit.c

···
+#include <linux/init.h>
+#include <linux/types.h>
+#include <asm/unistd32.h>
+
+unsigned compat_dir_class[] = {
+#include <asm-generic/audit_dir_write.h>
+~0U
+};
+
+unsigned compat_read_class[] = {
+#include <asm-generic/audit_read.h>
+~0U
+};
+
+unsigned compat_write_class[] = {
+#include <asm-generic/audit_write.h>
+~0U
+};
+
+unsigned compat_chattr_class[] = {
+#include <asm-generic/audit_change_attr.h>
+~0U
+};
+
+unsigned compat_signal_class[] = {
+#include <asm-generic/audit_signal.h>
+~0U
+};
+
+int audit_classify_compat_syscall(int abi, unsigned syscall)
+{
+	switch (syscall) {
+#ifdef __NR_open
+	case __NR_open:
+		return 2;
+#endif
+#ifdef __NR_openat
+	case __NR_openat:
+		return 3;
+#endif
+#ifdef __NR_socketcall
+	case __NR_socketcall:
+		return 4;
+#endif
+	case __NR_execve:
+		return 5;
+	default:
+		return 1;
+	}
+}