From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com ([209.85.220.45]:35787 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965025AbcIWH1O (ORCPT ); Fri, 23 Sep 2016 03:27:14 -0400 Received: by mail-pa0-f45.google.com with SMTP id oz2so37595225pac.2 for ; Fri, 23 Sep 2016 00:27:14 -0700 (PDT) From: AKASHI Takahiro To: catalin.marinas@arm.com, will.deacon@arm.com, jason.wessel@windriver.com Cc: linux-arm-kernel@lists.infradead.org, kgdb-bugreport@lists.sourceforge.net, stable@vger.kernel.org, AKASHI Takahiro Subject: [PATCH v2 3/3] arm64: kgdb: disable interrupts while a software step is enabled Date: Fri, 23 Sep 2016 16:33:27 +0900 Message-Id: <20160923073327.9657-4-takahiro.akashi@linaro.org> In-Reply-To: <20160923073327.9657-1-takahiro.akashi@linaro.org> References: <20160923073327.9657-1-takahiro.akashi@linaro.org> Sender: stable-owner@vger.kernel.org List-ID: After entering kgdb mode, 'stepi' may unexpectedly breaks the execution somewhere in el1_irq. This happens because a debug exception is always enabled in el1_irq due to the following commit merged in v3.16: commit 2a2830703a23 ("arm64: debug: avoid accessing mdscr_el1 on fault paths where possible") A pending interrupt can be taken after kgdb has enabled a software step, but before a debug exception is actually taken. This patch enforces interrupts to be masked while single stepping. Signed-off-by: AKASHI Takahiro Cc: Catalin Marinas Cc: Will Deacon Cc: Jason Wessel Cc: # 3.16- --- arch/arm64/kernel/kgdb.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c index 59c4aec..6732a27 100644 --- a/arch/arm64/kernel/kgdb.c +++ b/arch/arm64/kernel/kgdb.c @@ -26,6 +26,7 @@ #include #include #include +#include #include struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = { @@ -109,6 +110,7 @@ struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = { { "fpcr", 4, -1 }, }; +static DEFINE_PER_CPU(unsigned int, kgdb_pstate); static DEFINE_PER_CPU(struct irq_work, kgdb_irq_work); char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs) @@ -198,6 +200,10 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, err = 0; break; case 's': + /* mask interrupts while single stepping */ + __this_cpu_write(kgdb_pstate, linux_regs->pstate); + linux_regs->pstate |= PSR_I_BIT; + /* * Update step address value with address passed * with step packet. @@ -239,9 +245,18 @@ NOKPROBE_SYMBOL(kgdb_compiled_brk_fn); static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr) { + unsigned int pstate; + kernel_disable_single_step(); atomic_set(&kgdb_cpu_doing_single_step, -1); + /* restore interrupt mask status */ + pstate = __this_cpu_read(kgdb_pstate); + if (pstate & PSR_I_BIT) + regs->pstate |= PSR_I_BIT; + else + regs->pstate &= ~PSR_I_BIT; + kgdb_handle_exception(1, SIGTRAP, 0, regs); return 0; } -- 2.10.0