From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 327DE1A075F for ; Fri, 17 Jul 2015 08:42:52 +1000 (AEST) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 6FEE61402A9 for ; Fri, 17 Jul 2015 08:42:51 +1000 (AEST) Message-ID: <1437086551.28088.48.camel@kernel.crashing.org> Subject: Re: [RFC PATCH 02/12] powerpc/kernel: Switch to using MAX_ERRNO From: Benjamin Herrenschmidt To: Michael Ellerman Cc: linuxppc-dev@ozlabs.org, wad@chromium.org, keescook@chromium.org, linux-kernel@vger.kernel.org, luto@amacapital.net, strosake@linux.vnet.ibm.com, bogdan.purcareata@freescale.com Date: Fri, 17 Jul 2015 08:42:31 +1000 In-Reply-To: <1436945834-26660-2-git-send-email-mpe@ellerman.id.au> References: <1436945834-26660-1-git-send-email-mpe@ellerman.id.au> <1436945834-26660-2-git-send-email-mpe@ellerman.id.au> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2015-07-15 at 17:37 +1000, Michael Ellerman wrote: > Currently on powerpc we have our own #define for the highest (negative) > errno value, called _LAST_ERRNO. This is defined to be 516, for reasons > which are not clear. > > The generic code, and x86, use MAX_ERRNO, which is defined to be 4095. > > In particular seccomp uses MAX_ERRNO to restrict the value that a > seccomp filter can return. > > Currently with the mismatch between _LAST_ERRNO and MAX_ERRNO, a seccomp > tracer wanting to return 600, expecting it to be seen as an error, would > instead find on powerpc that userspace sees a successful syscall with a > return value of 600. > > To avoid this inconsistency, switch powerpc to use MAX_ERRNO. > > We are somewhat confident that generic syscalls that can return a > non-error value above negative MAX_ERRNO have already been updated to > use force_successful_syscall_return(). > > I have also checked all the powerpc specific syscalls, and believe that > none of them expect to return a non-error value between -MAX_ERRNO and > -516. So this change should be safe ... > > Signed-off-by: Michael Ellerman Acked-by: Benjamin Herrenschmidt > --- > arch/powerpc/include/uapi/asm/errno.h | 2 -- > arch/powerpc/kernel/entry_32.S | 3 ++- > arch/powerpc/kernel/entry_64.S | 5 +++-- > 3 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/powerpc/include/uapi/asm/errno.h b/arch/powerpc/include/uapi/asm/errno.h > index 8c145fd17d86..e8b6b5f7de7c 100644 > --- a/arch/powerpc/include/uapi/asm/errno.h > +++ b/arch/powerpc/include/uapi/asm/errno.h > @@ -6,6 +6,4 @@ > #undef EDEADLOCK > #define EDEADLOCK 58 /* File locking deadlock error */ > > -#define _LAST_ERRNO 516 > - > #endif /* _ASM_POWERPC_ERRNO_H */ > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S > index 46fc0f4d8982..67ecdf61f4e3 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -20,6 +20,7 @@ > */ > > #include > +#include > #include > #include > #include > @@ -354,7 +355,7 @@ ret_from_syscall: > SYNC > MTMSRD(r10) > lwz r9,TI_FLAGS(r12) > - li r8,-_LAST_ERRNO > + li r8,-MAX_ERRNO > andi. r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK) > bne- syscall_exit_work > cmplw 0,r3,r8 > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > index 0796c487d3db..8292581a42f1 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -19,6 +19,7 @@ > */ > > #include > +#include > #include > #include > #include > @@ -207,7 +208,7 @@ system_call: /* label this so stack traces look sane */ > #endif /* CONFIG_PPC_BOOK3E */ > > ld r9,TI_FLAGS(r12) > - li r11,-_LAST_ERRNO > + li r11,-MAX_ERRNO > andi. r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK) > bne- syscall_exit_work > cmpld r3,r11 > @@ -279,7 +280,7 @@ syscall_exit_work: > beq+ 0f > REST_NVGPRS(r1) > b 2f > -0: cmpld r3,r11 /* r10 is -LAST_ERRNO */ > +0: cmpld r3,r11 /* r11 is -MAX_ERRNO */ > blt+ 1f > andi. r0,r9,_TIF_NOERROR > bne- 1f