| Message ID | 20170630123906.8865-3-ebiederm@xmission.com |
|---|---|
| State | Not Applicable |
| Delegated to: | David Miller |
| Headers | show |
From: "Eric W. Biederman" <ebiederm@xmission.com> Date: Fri, 30 Jun 2017 07:39:01 -0500 > 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 */ It's one thing to say FIXME in a comment in a kernel local header or C file. It's quite another to put this into the name of a macro which has visibility in the global user compilation namespace. I don't think you should really do that. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David Miller <davem@davemloft.net> writes: > From: "Eric W. Biederman" <ebiederm@xmission.com> > Date: Fri, 30 Jun 2017 07:39:01 -0500 > >> 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 */ > > It's one thing to say FIXME in a comment in a kernel local header or > C file. > > It's quite another to put this into the name of a macro which has > visibility in the global user compilation namespace. > > I don't think you should really do that. Good point. Sigh. It almost fits because we did do something off in the uapi exported to userspace and we don't have a header file definition for that case. Still. At this point arch/sparc/include/asm/siginfo.h is a better fit for that definition. I will respin and fix that. I wish I knew what would make a better default floating point si_code on sparc. Using 0 aka SI_USER is doesn't fit at all. Sigh. Unfortunately I don't know the architecture well enough to even guess what is going on in do_fpe_common when when no bits in fsr are set. Any suggests for a better fix than just documenting that linux does something weird and ill advised here? Eric -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
ebiederm@xmission.com (Eric W. Biederman) writes: > David Miller <davem@davemloft.net> writes: > >> From: "Eric W. Biederman" <ebiederm@xmission.com> >> Date: Fri, 30 Jun 2017 07:39:01 -0500 >> >>> 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 */ >> >> It's one thing to say FIXME in a comment in a kernel local header or >> C file. >> >> It's quite another to put this into the name of a macro which has >> visibility in the global user compilation namespace. >> >> I don't think you should really do that. > > Good point. > > Sigh. It almost fits because we did do something off in the uapi > exported to userspace and we don't have a header file definition for > that case. > > Still. At this point arch/sparc/include/asm/siginfo.h is > a better fit for that definition. > > I will respin and fix that. Except arch/<arch>/include/asm/siginfo.h has now been eliminated. So these definitions have to be #ifdef __KERNEL__ #define ..._FIXME #endif In the uapi but not visible in the headers outside of the kernel. Which seems appropriate for these values. Eric -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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;
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" <davem@davemloft.net> Cc: sparclinux@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- 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(-)