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[81.231.232.130]) by smtp.gmail.com with ESMTPSA id t8sm1475806lfe.31.2020.04.21.00.47.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2020 00:47:13 -0700 (PDT) Date: Tue, 21 Apr 2020 09:48:24 +0200 From: "Edgar E. Iglesias" To: Peter Maydell Subject: Re: [PATCH 1/4] linux-user/arm: BKPT should cause SIGTRAP, not be a syscall Message-ID: <20200421074824.GF2669@toto> References: <20200420212206.12776-1-peter.maydell@linaro.org> <20200420212206.12776-2-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200420212206.12776-2-peter.maydell@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Received-SPF: pass client-ip=2a00:1450:4864:20::143; envelope-from=edgar.iglesias@gmail.com; helo=mail-lf1-x143.google.com X-detected-operating-system: by eggs.gnu.org: Error: [-] PROGRAM ABORT : Malformed IPv6 address (bad octet value). Location : parse_addr6(), p0f-client.c:67 X-Received-From: 2a00:1450:4864:20::143 X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: omerg681@gmail.com, qemu-arm@nongnu.org, Riku Voipio , qemu-devel@nongnu.org, Laurent Vivier Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-arm" X-TUID: agiPK9/jAUR1 On Mon, Apr 20, 2020 at 10:22:03PM +0100, Peter Maydell wrote: > In linux-user/arm/cpu-loop.c we incorrectly treat EXCP_BKPT similarly > to EXCP_SWI, which means that if the guest executes a BKPT insn then > QEMU will perform a syscall for it (which syscall depends on what > value happens to be in r7...). The correct behaviour is that the > guest process should take a SIGTRAP. > > This code has been like this (more or less) since commit > 06c949e62a098f in 2006 which added BKPT in the first place. This is > probably because at the time the same code path was used to handle > both Linux syscalls and semihosting calls, and (on M profile) BKPT > with a suitable magic number is used for semihosting calls. But > these days we've moved handling of semihosting out to an entirely > different codepath, so we can fix this bug by simply removing this > handling of EXCP_BKPT and instead making it deliver a SIGTRAP like > EXCP_DEBUG (as we do already on aarch64). > > Reported-by: > Fixes: https://bugs.launchpad.net/qemu/+bug/1873898 > Signed-off-by: Peter Maydell Reviewed-by: Edgar E. Iglesias > --- > linux-user/arm/cpu_loop.c | 30 ++++++++---------------------- > 1 file changed, 8 insertions(+), 22 deletions(-) > > diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c > index cf618daa1ca..82d0dd3c312 100644 > --- a/linux-user/arm/cpu_loop.c > +++ b/linux-user/arm/cpu_loop.c > @@ -295,32 +295,17 @@ void cpu_loop(CPUARMState *env) > } > break; > case EXCP_SWI: > - case EXCP_BKPT: > { > env->eabi = 1; > /* system call */ > - if (trapnr == EXCP_BKPT) { > - if (env->thumb) { > - /* FIXME - what to do if get_user() fails? */ > - get_user_code_u16(insn, env->regs[15], env); > - n = insn & 0xff; > - env->regs[15] += 2; > - } else { > - /* FIXME - what to do if get_user() fails? */ > - get_user_code_u32(insn, env->regs[15], env); > - n = (insn & 0xf) | ((insn >> 4) & 0xff0); > - env->regs[15] += 4; > - } > + if (env->thumb) { > + /* FIXME - what to do if get_user() fails? */ > + get_user_code_u16(insn, env->regs[15] - 2, env); > + n = insn & 0xff; > } else { > - if (env->thumb) { > - /* FIXME - what to do if get_user() fails? */ > - get_user_code_u16(insn, env->regs[15] - 2, env); > - n = insn & 0xff; > - } else { > - /* FIXME - what to do if get_user() fails? */ > - get_user_code_u32(insn, env->regs[15] - 4, env); > - n = insn & 0xffffff; > - } > + /* FIXME - what to do if get_user() fails? */ > + get_user_code_u32(insn, env->regs[15] - 4, env); > + n = insn & 0xffffff; > } > > if (n == ARM_NR_cacheflush) { > @@ -396,6 +381,7 @@ void cpu_loop(CPUARMState *env) > } > break; > case EXCP_DEBUG: > + case EXCP_BKPT: > excp_debug: > info.si_signo = TARGET_SIGTRAP; > info.si_errno = 0; > -- > 2.20.1 > >