From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EEAC513D520 for ; Tue, 14 Jan 2025 14:53:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736866407; cv=none; b=BK4xdDKETpOz5WUEshvTFV28tAnZRE5Rcm6aZTXkalJPj5CrFtvXqLhQGbnCmIjyGI1Ini2TnJXPDKnaEibh96XFzcdwuCbatsdqI+8AprLStBi/JS1iQz9+bbaVM8vUHg+UdQQEHAdYNR/Tgd6ubMFtd95q3dMd8EpZFAGdWUg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736866407; c=relaxed/simple; bh=MLxWvNuHvrzVQA3rWXD9Jq5n8QtB9LWjCoeozHXX6h4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WxXgGqoKk0ceb+sl+kIAO4DJ+iRSwjXJ81W45+kHbWvcvHMZv0h5LTGnksU39XsNJ5SXagJ255HqQBV9/n3m2Gh11oQHE0J8Y0reQpCdULbbGkClcHmqD8eTvXfdL8XjWgvcf5kDSElOHVn/WzuYk9FtVS/Q9ik0dzpSgTZVBKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GTsoqL4s; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GTsoqL4s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BFD6C4CEDD; Tue, 14 Jan 2025 14:53:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736866406; bh=MLxWvNuHvrzVQA3rWXD9Jq5n8QtB9LWjCoeozHXX6h4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GTsoqL4sltE3LtRbnFeEfoDTvimp557zuR6CSUzBFqV9DPWA5rQXXwAgMF/AbDewj SHcrhXfNafUqKJYmD83OSsnaK+yLevQrPlSciAqoNbyvV3jZCyPNGUONI3Da3lqPDW +W3uf4xDbN7XsbK5N1F6+baisPzNF26lAj+32/o5AnnjX720g86xUuAW8FC8mz6Ns3 LyhfDm3eAfP2rcp0rec41mjRfetwc3d5HtKVeRkeHnMyyKYQQF8LNz29tWNRcQDrvG gKGJ/gaRQJOk+2Sbd0mRHgdStcZf1kSv4V7jOiKQZQvX40Z4gRk3BeFyv9vYR6DmYL qwJQdLlR2I8aw== Date: Tue, 14 Jan 2025 15:53:20 +0100 From: Alexey Gladkov To: "Dmitry V. Levin" Cc: Oleg Nesterov , Michael Ellerman , Eugene Syromyatnikov , Mike Frysinger , Renzo Davoli , Davide Berardi , strace-devel@lists.strace.io, Madhavan Srinivasan , Nicholas Piggin , Christophe Leroy , Naveen N Rao , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/7] powerpc: properly negate error in syscall_set_return_value() Message-ID: References: <20250113170925.GA392@strace.io> <20250113171054.GA589@strace.io> <20250114134844.GA10630@strace.io> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250114134844.GA10630@strace.io> On Tue, Jan 14, 2025 at 03:48:44PM +0200, Dmitry V. Levin wrote: > On Tue, Jan 14, 2025 at 02:00:16PM +0100, Alexey Gladkov wrote: > > On Mon, Jan 13, 2025 at 07:10:54PM +0200, Dmitry V. Levin wrote: > > > Bring syscall_set_return_value() in sync with syscall_get_error(), > > > and let upcoming ptrace/set_syscall_info selftest pass on powerpc. > > > > > > This reverts commit 1b1a3702a65c ("powerpc: Don't negate error in > > > syscall_set_return_value()"). > > > > > > Signed-off-by: Dmitry V. Levin > > > --- > > > arch/powerpc/include/asm/syscall.h | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h > > > index 3dd36c5e334a..422d7735ace6 100644 > > > --- a/arch/powerpc/include/asm/syscall.h > > > +++ b/arch/powerpc/include/asm/syscall.h > > > @@ -82,7 +82,11 @@ static inline void syscall_set_return_value(struct task_struct *task, > > > */ > > > if (error) { > > > regs->ccr |= 0x10000000L; > > > - regs->gpr[3] = error; > > > + /* > > > + * In case of an error regs->gpr[3] contains > > > + * a positive ERRORCODE. > > > + */ > > > + regs->gpr[3] = -error; > > > > After this change the syscall_get_error() will return positive value if > > the system call failed. Since syscall_get_error() still believes > > regs->gpr[3] is still positive in case !trap_is_scv(). > > > > Or am I missing something? > > syscall_get_error() does the following in case of !trap_is_scv(): > > /* > * If the system call failed, > * regs->gpr[3] contains a positive ERRORCODE. > */ > return (regs->ccr & 0x10000000UL) ? -regs->gpr[3] : 0; > > That is, in !trap_is_scv() case it assumes that regs->gpr[3] is positive > and is going to return a negative value (-ERRORCODE). Yeah. Now I see it. if (trap_is_scv(regs)) { regs->result = -EINTR; regs->gpr[3] = -EINTR; } else { regs->result = -EINTR; regs->gpr[3] = EINTR; regs->ccr |= 0x10000000; } Two different APIs imply gpr[3] with a different sign. You can add: Reviewed-by: Alexey Gladkov > > It looks like the selftest you mentioned in the commit message doesn't > > check the !trap_is_scv() branch. > > The selftest is architecture-agnostic, it just executes syscalls and > checks whether the data returned by PTRACE_GET_SYSCALL_INFO meets > expectations. Do you mean that syscall() is not good enough for syscall > invocation from coverage perspective on powerpc? > > See also commit d72500f99284 ("powerpc/64s/syscall: Fix ptrace syscall > info with scv syscalls"). > > > -- > ldv -- Rgrds, legion