The following reply was made to PR amd64/169927; it has been noted by GNATS.
From: Mark Linimon <[email protected]> To: [email protected] Cc: Subject: Re: amd64/169927: siginfo, si_code for fpe errors when error occurs using the SSE math processor Date: Tue, 17 Jul 2012 16:50:18 -0500 ----- Forwarded message from Konstantin Belousov <[email protected]> ----- Date: Tue, 17 Jul 2012 21:26:19 +0300 From: Konstantin Belousov <[email protected]> To: Bruce Evans <[email protected]> Cc: [email protected] Subject: Re: amd64/169927: siginfo, si_code for fpe errors when error occurs using the SSE math processor On Tue, Jul 17, 2012 at 08:09:15PM +0300, Konstantin Belousov wrote: > The trap number is available for SA_SIGINFO type of handlers with > si_trapno member of siginfo_t. I think this is final argument to have > separate fputrap_{x87,sse} functions. > > For amd64, SSE hardware is FPU, so I do not see much wrong with the name. > > I changed fputrap_sse() according to your suggestion. Below is the actually tested patch. After it, I put the test program. diff --git a/sys/amd64/amd64/fpu.c b/sys/amd64/amd64/fpu.c index a7812b7..ae241ce 100644 --- a/sys/amd64/amd64/fpu.c +++ b/sys/amd64/amd64/fpu.c @@ -73,6 +73,7 @@ __FBSDID("$FreeBSD$"); #define fxrstor(addr) __asm __volatile("fxrstor %0" : : "m" (*(addr))) #define fxsave(addr) __asm __volatile("fxsave %0" : "=m" (*(addr))) #define ldmxcsr(csr) __asm __volatile("ldmxcsr %0" : : "m" (csr)) +#define stmxcsr(addr) __asm __volatile("stmxcsr %0" : : "m" (*(addr))) static __inline void xrstor(char *addr, uint64_t mask) @@ -105,6 +106,7 @@ void fnstsw(caddr_t addr); void fxsave(caddr_t addr); void fxrstor(caddr_t addr); void ldmxcsr(u_int csr); +void stmxcsr(u_int csr); void xrstor(char *addr, uint64_t mask); void xsave(char *addr, uint64_t mask); @@ -113,9 +115,6 @@ void xsave(char *addr, uint64_t mask); #define start_emulating() load_cr0(rcr0() | CR0_TS) #define stop_emulating() clts() -#define GET_FPU_CW(thread) ((thread)->td_pcb->pcb_save->sv_env.en_cw) -#define GET_FPU_SW(thread) ((thread)->td_pcb->pcb_save->sv_env.en_sw) - CTASSERT(sizeof(struct savefpu) == 512); CTASSERT(sizeof(struct xstate_hdr) == 64); CTASSERT(sizeof(struct savefpu_ymm) == 832); @@ -514,11 +513,15 @@ static char fpetable[128] = { }; /* - * Preserve the FP status word, clear FP exceptions, then generate a SIGFPE. + * Preserve the FP status word, clear FP exceptions for x87, then + * generate a SIGFPE. + * + * Clearing exceptions was necessary mainly to avoid IRQ13 bugs and is + * engraved in our i386 ABI. We now depend on longjmp() restoring a + * usable state. Restoring the state or examining it might fail if we + * didn't clear exceptions. * - * Clearing exceptions is necessary mainly to avoid IRQ13 bugs. We now - * depend on longjmp() restoring a usable state. Restoring the state - * or examining it might fail if we didn't clear exceptions. + * For SSE exceptions, the exceptions are not cleared. * * The error code chosen will be one of the FPE_... macros. It will be * sent as the second argument to old BSD-style signal handlers and as @@ -531,8 +534,9 @@ static char fpetable[128] = { * solution for signals other than SIGFPE. */ int -fputrap() +fputrap_x87(void) { + struct savefpu *pcb_save; u_short control, status; critical_enter(); @@ -543,19 +547,40 @@ fputrap() * wherever they are. */ if (PCPU_GET(fpcurthread) != curthread) { - control = GET_FPU_CW(curthread); - status = GET_FPU_SW(curthread); + pcb_save = curthread->td_pcb->pcb_save; + control = pcb_save->sv_env.en_cw; + status = pcb_save->sv_env.en_sw; } else { fnstcw(&control); fnstsw(&status); + fnclex(); } - if (PCPU_GET(fpcurthread) == curthread) - fnclex(); critical_exit(); return (fpetable[status & ((~control & 0x3f) | 0x40)]); } +int +fputrap_sse(void) +{ + u_int mxcsr; + + critical_enter(); + + /* + * Coomparing with the x87 #MF handler, we do not clear + * exceptions from the mxcsr. + */ + if (PCPU_GET(fpcurthread) != curthread) + mxcsr = curthread->td_pcb->pcb_save->sv_env.en_mxcsr; + else + stmxcsr(&mxcsr); + + critical_exit(); + + return (fpetable[(mxcsr & (~mxcsr >> 7)) & 0x3f]); +} + /* * Implement device not available (DNA) exception * diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c index 75e15e0..57d1cc2 100644 --- a/sys/amd64/amd64/trap.c +++ b/sys/amd64/amd64/trap.c @@ -328,7 +328,7 @@ trap(struct trapframe *frame) break; case T_ARITHTRAP: /* arithmetic trap */ - ucode = fputrap(); + ucode = fputrap_x87(); if (ucode == -1) goto userout; i = SIGFPE; @@ -442,7 +442,9 @@ trap(struct trapframe *frame) break; case T_XMMFLT: /* SIMD floating-point exception */ - ucode = 0; /* XXX */ + ucode = fputrap_sse(); + if (ucode == -1) + goto userout; i = SIGFPE; break; } diff --git a/sys/amd64/include/fpu.h b/sys/amd64/include/fpu.h index 98a016b..7d0f0ea 100644 --- a/sys/amd64/include/fpu.h +++ b/sys/amd64/include/fpu.h @@ -62,7 +62,8 @@ int fpusetregs(struct thread *td, struct savefpu *addr, char *xfpustate, size_t xfpustate_size); int fpusetxstate(struct thread *td, char *xfpustate, size_t xfpustate_size); -int fputrap(void); +int fputrap_sse(void); +int fputrap_x87(void); void fpuuserinited(struct thread *td); struct fpu_kern_ctx *fpu_kern_alloc_ctx(u_int flags); void fpu_kern_free_ctx(struct fpu_kern_ctx *ctx); fpuex.c: /* $Id: fpuex.c,v 1.2 2012/07/17 18:22:54 kostik Exp kostik $ */ #include <sys/types.h> #include <err.h> #include <errno.h> #include <signal.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ucontext.h> #if defined(__amd64__) #include <machine/fpu.h> #elif defined(__i386__) #include <machine/npx.h> #endif static void handler(int signo __unused, siginfo_t *info, void *v) { ucontext_t *uap; mcontext_t *mc; #if defined(__amd64__) struct savefpu *sf; #elif defined(__i386__) struct savexmm *sf; #endif uap = v; mc = &uap->uc_mcontext; sf = &mc->mc_fpstate; printf("intr handler: trapno %d code %d cw 0x%04x sw 0x%04x mxcsr 0x%08x ip 0x%lx\n", info->si_trapno, info->si_code, #if defined(__amd64__) sf->sv_env.en_cw, sf->sv_env.en_sw, sf->sv_env.en_mxcsr, sf->sv_env.en_rip #elif defined(__i386__) sf->sv_env.en_cw, sf->sv_env.en_sw, sf->sv_env.en_mxcsr, (unsigned long)sf->sv_env.en_fip #endif ); exit(0); } double a[3]; double x(void) __attribute__((noinline)); double x(void) { a[3] = a[0] / a[1]; return (a[3]); } int main(void) { struct sigaction sa; uint32_t mxcsr; uint16_t cw; bzero(&sa, sizeof(sa)); sa.sa_sigaction = handler; sa.sa_flags = SA_SIGINFO; if (sigaction(SIGFPE, &sa, NULL) == -1) err(1, "sigaction SIGFPE"); mxcsr = 0; __asm __volatile("ldmxcsr %0" : : "m" (mxcsr)); #ifdef __i386__ cw = 0; __asm __volatile("fldcw %0" : : "m" (cw)); #endif a[0] = 1.0; a[1] = 0.0; x(); return (0); } ----- End forwarded message ----- _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-amd64 To unsubscribe, send any mail to "[email protected]"
