From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38286 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752556AbeENJrq (ORCPT ); Mon, 14 May 2018 05:47:46 -0400 From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, dave.martin@arm.com, james.morse@arm.com, linux@dominikbrodowski.net, linux-fsdevel@vger.kernel.org, marc.zyngier@arm.com, mark.rutland@arm.com, viro@zeniv.linux.org.uk, will.deacon@arm.com Subject: [PATCH 09/18] arm64: convert syscall trace logic to C Date: Mon, 14 May 2018 10:46:31 +0100 Message-Id: <20180514094640.27569-10-mark.rutland@arm.com> In-Reply-To: <20180514094640.27569-1-mark.rutland@arm.com> References: <20180514094640.27569-1-mark.rutland@arm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Currently syscall tracing is a tricky assembly state machine, which can be rather difficult to follow, and even harder to modify. Before we start fiddling with it for pt_regs syscalls, let's convert it to C. This is not intended to have any functional change. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Will Deacon --- arch/arm64/kernel/entry.S | 53 ++---------------------------------------- arch/arm64/kernel/syscall.c | 56 +++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 56 insertions(+), 53 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d6e057500eaf..5c60369b52fc 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -866,24 +866,6 @@ el0_error_naked: b ret_to_user ENDPROC(el0_error) - -/* - * This is the fast syscall return path. We do as little as possible here, - * and this includes saving x0 back into the kernel stack. - */ -ret_fast_syscall: - disable_daif - ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing - and x2, x1, #_TIF_SYSCALL_WORK - cbnz x2, ret_fast_syscall_trace - and x2, x1, #_TIF_WORK_MASK - cbnz x2, work_pending - enable_step_tsk x1, x2 - kernel_exit 0 -ret_fast_syscall_trace: - enable_daif - b __sys_trace_return_skipped // we already saved x0 - /* * Ok, we need to do extra processing, enter the slow path. */ @@ -939,44 +921,13 @@ alternative_else_nop_endif #endif el0_svc_naked: // compat entry point - stp x0, xscno, [sp, #S_ORIG_X0] // save the original x0 and syscall number - enable_daif - ct_user_exit 1 - - tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks - b.ne __sys_trace mov x0, sp mov w1, wscno mov w2, wsc_nr mov x3, stbl - bl invoke_syscall - b ret_fast_syscall -ENDPROC(el0_svc) - - /* - * This is the really slow path. We're going to be doing context - * switches, and waiting for our parent to respond. - */ -__sys_trace: - cmp wscno, #NO_SYSCALL // user-issued syscall(-1)? - b.ne 1f - mov x0, #-ENOSYS // set default errno if so - str x0, [sp, #S_X0] -1: mov x0, sp - bl syscall_trace_enter - cmp w0, #NO_SYSCALL // skip the syscall? - b.eq __sys_trace_return_skipped - - mov x0, sp - mov w1, wscno - mov w2, wsc_nr - mov x3, stbl - bl invoke_syscall - -__sys_trace_return_skipped: - mov x0, sp - bl syscall_trace_exit + bl el0_svc_common b ret_to_user +ENDPROC(el0_svc) .popsection // .entry.text diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index 58d7569f47df..5df857e32b48 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -1,8 +1,13 @@ // SPDX-License-Identifier: GPL-2.0 +#include +#include #include #include +#include +#include + long do_ni_syscall(struct pt_regs *regs); typedef long (*syscall_fn_t)(unsigned long, unsigned long, @@ -16,8 +21,8 @@ static void __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) regs->regs[4], regs->regs[5]); } -asmlinkage void invoke_syscall(struct pt_regs *regs, int scno, int sc_nr, - syscall_fn_t syscall_table[]) +static void invoke_syscall(struct pt_regs *regs, int scno, int sc_nr, + syscall_fn_t syscall_table[]) { if (scno < sc_nr) { syscall_fn_t syscall_fn; @@ -27,3 +32,50 @@ asmlinkage void invoke_syscall(struct pt_regs *regs, int scno, int sc_nr, regs->regs[0] = do_ni_syscall(regs); } } + +static inline bool has_syscall_work(unsigned long flags) +{ + return unlikely(flags & _TIF_SYSCALL_WORK); +} + +int syscall_trace_enter(struct pt_regs *regs); +void syscall_trace_exit(struct pt_regs *regs); + +asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, + syscall_fn_t syscall_table[]) +{ + unsigned long flags = current_thread_info()->flags; + + regs->orig_x0 = regs->regs[0]; + regs->syscallno = scno; + + local_daif_restore(DAIF_PROCCTX); + user_exit(); + + if (has_syscall_work(flags)) { + /* set default errno for user-issued syscall(-1) */ + if (scno == NO_SYSCALL) + regs->regs[0] = -ENOSYS; + scno = syscall_trace_enter(regs); + if (scno == NO_SYSCALL) + goto trace_exit; + } + + invoke_syscall(regs, scno, sc_nr, syscall_table); + + /* + * The tracing status may have changed under our feet, so we have to + * check again. However, if we were tracing entry, then we always trace + * exit regardless, as the old entry assembly did. + */ + if (!has_syscall_work(flags)) { + local_daif_mask(); + flags = current_thread_info()->flags; + if (!has_syscall_work(flags)) + return; + local_daif_restore(DAIF_PROCCTX); + } + +trace_exit: + syscall_trace_exit(regs); +} -- 2.11.0