From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eric W. Biederman" Subject: [PATCH 3/8] signal/sparc: Document a conflict with SI_USER with SIGFPE Date: Fri, 30 Jun 2017 07:39:01 -0500 Message-ID: <20170630123906.8865-3-ebiederm@xmission.com> References: <87efu22set.fsf@xmission.com> Return-path: In-Reply-To: <87efu22set.fsf@xmission.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Linus Torvalds , Al Viro , Oleg Nesterov , Andrei Vagin , Thomas Gleixner , Greg KH , Andrey Vagin , Serge Hallyn , Pavel Emelyanov , Cyrill Gorcunov , Peter Zijlstra , Willy Tarreau , linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Linux Containers , Michael Kerrisk , "Eric W. Biederman" , "David S. Miller" , sparclinux@vger.kernel.org List-Id: linux-api@vger.kernel.org Setting si_code to __SI_FAULT results in a userspace seeing an si_code of 0. This is the same si_code as SI_USER. Posix and common sense requires that SI_USER not be a signal specific si_code. As such this use of 0 for the si_code is a pretty horribly broken ABI. This was introduced in 2.3.41 so this mess has had a long time for people to be able to start depending on it. As this bug has existed for 17 years already I don't know if it is worth fixing. It is definitely worth documenting what is going on so that no one decides to copy this bad decision. Cc: "David S. Miller" Cc: sparclinux@vger.kernel.org Signed-off-by: "Eric W. Biederman" --- arch/sparc/include/uapi/asm/siginfo.h | 5 +++++ arch/sparc/kernel/traps_32.c | 2 +- arch/sparc/kernel/traps_64.c | 2 +- 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/sparc/include/uapi/asm/siginfo.h b/arch/sparc/include/uapi/asm/siginfo.h index 2d9b79ccaa50..6bc5c677e92f 100644 --- a/arch/sparc/include/uapi/asm/siginfo.h +++ b/arch/sparc/include/uapi/asm/siginfo.h @@ -17,6 +17,11 @@ #define SI_NOINFO 32767 /* no information in siginfo_t */ /* + * SIGFPE si_codes + */ +#define FPE_FIXME (__SI_FAULT|0) /* Broken dup of SI_USER */ + +/* * SIGEMT si_codes */ #define EMT_TAGOVF (__SI_FAULT|1) /* tag overflow */ diff --git a/arch/sparc/kernel/traps_32.c b/arch/sparc/kernel/traps_32.c index 466d4aed06c7..581cf35ee7e3 100644 --- a/arch/sparc/kernel/traps_32.c +++ b/arch/sparc/kernel/traps_32.c @@ -306,7 +306,7 @@ void do_fpe_trap(struct pt_regs *regs, unsigned long pc, unsigned long npc, info.si_errno = 0; info.si_addr = (void __user *)pc; info.si_trapno = 0; - info.si_code = __SI_FAULT; + info.si_code = FPE_FIXME; if ((fsr & 0x1c000) == (1 << 14)) { if (fsr & 0x10) info.si_code = FPE_FLTINV; diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c index 196ee5eb4d48..e882e128faa3 100644 --- a/arch/sparc/kernel/traps_64.c +++ b/arch/sparc/kernel/traps_64.c @@ -2258,7 +2258,7 @@ static void do_fpe_common(struct pt_regs *regs) info.si_errno = 0; info.si_addr = (void __user *)regs->tpc; info.si_trapno = 0; - info.si_code = __SI_FAULT; + info.si_code = FPE_FIXME; if ((fsr & 0x1c000) == (1 << 14)) { if (fsr & 0x10) info.si_code = FPE_FLTINV; -- 2.10.1