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Commit c87a8517 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Kees Cook
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x86/entry: Get rid of two-phase syscall entry work 



I added two-phase syscall entry work back when the entry slow path
was very slow.  Nowadays, the entry slow path is fast and two-phase
entry work serves no purpose.  Remove it.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 2f275de5

arch/x86/entry/common.c

+8 −76
Original line number Diff line number Diff line
@@ -64,20 +64,13 @@ static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch) 
}



/*

 * We can return 0 to resume the syscall or anything else to go to phase

 * 2.  If we resume the syscall, we need to put something appropriate in

 * regs->orig_ax.

 *

 * NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax

 * are fully functional.

 *

 * For phase 2's benefit, our return value is:

 * 0:			resume the syscall

 * 1:			go to phase 2; no seccomp phase 2 needed

 * anything else:	go to phase 2; pass return value to seccomp

 * Returns the syscall nr to run (which should match regs->orig_ax) or -1

 * to skip the syscall.

 */

unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)

static long syscall_trace_enter(struct pt_regs *regs)

{

	u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;



	struct thread_info *ti = pt_regs_to_thread_info(regs);

	unsigned long ret = 0;

	u32 work;
@@ -118,59 +111,9 @@ unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch) 
			sd.args[5] = regs->bp;

		}



		BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);

		BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);



		ret = seccomp_phase1(&sd);

		if (ret == SECCOMP_PHASE1_SKIP) {

			regs->orig_ax = -1;

			ret = 0;

		} else if (ret != SECCOMP_PHASE1_OK) {

			return ret;  /* Go directly to phase 2 */

		}



		work &= ~_TIF_SECCOMP;

	}

#endif



	/* Do our best to finish without phase 2. */

	if (work == 0)

		return ret;  /* seccomp and/or nohz only (ret == 0 here) */



#ifdef CONFIG_AUDITSYSCALL

	if (work == _TIF_SYSCALL_AUDIT) {

		/*

		 * If there is no more work to be done except auditing,

		 * then audit in phase 1.  Phase 2 always audits, so, if

		 * we audit here, then we can't go on to phase 2.

		 */

		do_audit_syscall_entry(regs, arch);

		return 0;

	}

#endif



	return 1;  /* Something is enabled that we can't handle in phase 1 */

}



/* Returns the syscall nr to run (which should match regs->orig_ax). */

long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,

				unsigned long phase1_result)

{

	struct thread_info *ti = pt_regs_to_thread_info(regs);

	long ret = 0;

	u32 work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;



	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))

		BUG_ON(regs != task_pt_regs(current));



#ifdef CONFIG_SECCOMP

	/*

	 * Call seccomp_phase2 before running the other hooks so that

	 * they can see any changes made by a seccomp tracer.

	 */

	if (phase1_result > 1 && seccomp_phase2(phase1_result)) {

		/* seccomp failures shouldn't expose any additional code. */

		return -1;

		ret = __secure_computing(&sd);

		if (ret == -1)

			return ret;

	}

#endif
@@ -189,17 +132,6 @@ long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch, 
	return ret ?: regs->orig_ax;

}



long syscall_trace_enter(struct pt_regs *regs)

{

	u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;

	unsigned long phase1_result = syscall_trace_enter_phase1(regs, arch);



	if (phase1_result == 0)

		return regs->orig_ax;

	else

		return syscall_trace_enter_phase2(regs, arch, phase1_result);

}



#define EXIT_TO_USERMODE_LOOP_FLAGS				\

	(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |	\

	 _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)

arch/x86/include/asm/ptrace.h

+0 −6
Original line number Diff line number Diff line
@@ -83,12 +83,6 @@ extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, 
			 int error_code, int si_code);





extern unsigned long syscall_trace_enter_phase1(struct pt_regs *, u32 arch);

extern long syscall_trace_enter_phase2(struct pt_regs *, u32 arch,

				       unsigned long phase1_result);



extern long syscall_trace_enter(struct pt_regs *);



static inline unsigned long regs_return_value(struct pt_regs *regs)

{

	return regs->ax;