audit: Migrate to use SYSCALL_WORK flag

On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_AUDIT, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-9-krisman@collabora.com

include/asm-generic/syscall.h

@@ -43,9 +43,9 @@ int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
  * @regs:	task_pt_regs() of @task
  *
  * It's only valid to call this when @task is stopped for system
- * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
- * after tracehook_report_syscall_entry() returned nonzero to prevent
- * the system call from taking place.
+ * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT), after tracehook_report_syscall_entry()
+ * returned nonzero to prevent the system call from taking place.
  *
  * This rolls back the register state in @regs so it's as if the
  * system call instruction was a no-op.  The registers containing
@@ -63,7 +63,8 @@ void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
  * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
  *
  * It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
  */
 long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
 
@@ -76,7 +77,8 @@ long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
  * This value is meaningless if syscall_get_error() returned nonzero.
  *
  * It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
  */
 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
 
@@ -93,7 +95,8 @@ long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
  * code; the user sees a failed system call with this errno code.
  *
  * It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
  */
 void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
 			      int error, long val);
@@ -108,7 +111,8 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
 *  @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
  */
 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 			   unsigned long *args);
@@ -123,7 +127,8 @@ void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  * The first argument gets value @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
  */
 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 			   const unsigned long *args);
@@ -135,7 +140,7 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
  * Returns the AUDIT_ARCH_* based on the system call convention in use.
  *
  * It's only valid to call this when @task is stopped on entry to a system
- * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or
+ * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or
  * %SYSCALL_WORK_SECCOMP.
  *
  * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must

include/linux/entry-common.h

@@ -13,10 +13,6 @@
  * Define dummy _TIF work flags if not defined by the architecture or for
  * disabled functionality.
  */
-#ifndef _TIF_SYSCALL_AUDIT
-# define _TIF_SYSCALL_AUDIT		(0)
-#endif
-
 #ifndef _TIF_PATCH_PENDING
 # define _TIF_PATCH_PENDING		(0)
 #endif
@@ -36,9 +32,7 @@
 # define ARCH_SYSCALL_ENTER_WORK	(0)
 #endif
 
-#define SYSCALL_ENTER_WORK						\
-	(_TIF_SYSCALL_AUDIT  |						\
-	 ARCH_SYSCALL_ENTER_WORK)
+#define SYSCALL_ENTER_WORK ARCH_SYSCALL_ENTER_WORK
 
 /*
  * TIF flags handled in syscall_exit_to_user_mode()
@@ -47,16 +41,16 @@
 # define ARCH_SYSCALL_EXIT_WORK		(0)
 #endif
 
-#define SYSCALL_EXIT_WORK						\
-	(_TIF_SYSCALL_AUDIT |						\
-	 ARCH_SYSCALL_EXIT_WORK)
+#define SYSCALL_EXIT_WORK ARCH_SYSCALL_EXIT_WORK
 
 #define SYSCALL_WORK_ENTER	(SYSCALL_WORK_SECCOMP |			\
 				 SYSCALL_WORK_SYSCALL_TRACEPOINT |	\
 				 SYSCALL_WORK_SYSCALL_TRACE |		\
-				 SYSCALL_WORK_SYSCALL_EMU)
+				 SYSCALL_WORK_SYSCALL_EMU |		\
+				 SYSCALL_WORK_SYSCALL_AUDIT)
 #define SYSCALL_WORK_EXIT	(SYSCALL_WORK_SYSCALL_TRACEPOINT |	\
-				 SYSCALL_WORK_SYSCALL_TRACE)
+				 SYSCALL_WORK_SYSCALL_TRACE |		\
+				 SYSCALL_WORK_SYSCALL_AUDIT)
 
 /*
  * TIF flags handled in exit_to_user_mode_loop()

include/linux/thread_info.h

@@ -40,12 +40,14 @@ enum syscall_work_bit {
 	SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT,
 	SYSCALL_WORK_BIT_SYSCALL_TRACE,
 	SYSCALL_WORK_BIT_SYSCALL_EMU,
+	SYSCALL_WORK_BIT_SYSCALL_AUDIT,
 };
 
 #define SYSCALL_WORK_SECCOMP		BIT(SYSCALL_WORK_BIT_SECCOMP)
 #define SYSCALL_WORK_SYSCALL_TRACEPOINT	BIT(SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT)
 #define SYSCALL_WORK_SYSCALL_TRACE	BIT(SYSCALL_WORK_BIT_SYSCALL_TRACE)
 #define SYSCALL_WORK_SYSCALL_EMU	BIT(SYSCALL_WORK_BIT_SYSCALL_EMU)
+#define SYSCALL_WORK_SYSCALL_AUDIT	BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)
 
 #include <asm/thread_info.h>
 

kernel/auditsc.c

@@ -952,7 +952,7 @@ int audit_alloc(struct task_struct *tsk)
 
 	state = audit_filter_task(tsk, &key);
 	if (state == AUDIT_DISABLED) {
-		clear_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+		clear_task_syscall_work(tsk, SYSCALL_AUDIT);
 		return 0;
 	}
 
@@ -964,7 +964,7 @@ int audit_alloc(struct task_struct *tsk)
 	context->filterkey = key;
 
 	audit_set_context(tsk, context);
-	set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+	set_task_syscall_work(tsk, SYSCALL_AUDIT);
 	return 0;
 }