From 4e1102cf8c5bc9ae6a8371665ef6aa9de08e653a Mon Sep 17 00:00:00 2001 From: Mikael Pettersson Date: Sun, 17 Apr 2016 20:24:32 +0200 Subject: clean up FP exception code in sys_float.c This performs a number of cleanups in the FP exception code: - inline the body of unmask_fpe_conditional() in its only caller, then delete the duplicated and identical definitions of it - start the big processor-specific block with a comment describing the two functions that must be defined, then delete redundant comments at all the mask_*() functions - add a comment before fpe_sig_action() explaining exactly what processor-specific action is required of it - flatten #ifdef nesting in fpe_sig_action() - move common code in the x86 unmask_fpe() and erts_restore_fpu() function into a subroutine - minor tweaks: drop a redundant L suffix on a 0, add a comment after an #else, bump the size of a debug buffer, There should be no change in behaviour from these changes. --- erts/emulator/sys/unix/sys_float.c | 79 +++++++++++++++++--------------------- 1 file changed, 36 insertions(+), 43 deletions(-) (limited to 'erts/emulator/sys/unix/sys_float.c') diff --git a/erts/emulator/sys/unix/sys_float.c b/erts/emulator/sys/unix/sys_float.c index 8fe7e599e5..2ac35624fa 100644 --- a/erts/emulator/sys/unix/sys_float.c +++ b/erts/emulator/sys/unix/sys_float.c @@ -53,7 +53,7 @@ static void erts_init_fp_exception(void) void erts_thread_init_fp_exception(void) { unsigned long *fpe = erts_alloc(ERTS_ALC_T_FP_EXCEPTION, sizeof(*fpe)); - *fpe = 0L; + *fpe = 0; erts_tsd_set(fpe_key, fpe); } @@ -102,6 +102,17 @@ void erts_fp_check_init_error(volatile unsigned long *fpexnp) #define __DARWIN__ 1 #endif +/* + * Define two processor and possibly OS-specific primitives: + * + * static void unmask_fpe(void); + * -- unmask invalid, overflow, and divide-by-zero exceptions + * + * static int mask_fpe(void); + * -- mask invalid, overflow, and divide-by-zero exceptions + * -- return non-zero if the previous state was unmasked + */ + #if (defined(__i386__) || defined(__x86_64__)) && defined(__GNUC__) static void unmask_x87(void) @@ -113,7 +124,6 @@ static void unmask_x87(void) __asm__ __volatile__("fldcw %0" : : "m"(cw)); } -/* mask x87 FPE, return true if the previous state was unmasked */ static int mask_x87(void) { unsigned short cw; @@ -136,7 +146,6 @@ static void unmask_sse2(void) __asm__ __volatile__("ldmxcsr %0" : : "m"(mxcsr)); } -/* mask SSE2 FPE, return true if the previous state was unmasked */ static int mask_sse2(void) { unsigned int mxcsr; @@ -257,21 +266,19 @@ static int cpu_has_sse2(void) } #endif /* !__x86_64__ */ -static void unmask_fpe(void) +static void unmask_fpe_internal(void) { - __asm__ __volatile__("fnclex"); unmask_x87(); if (cpu_has_sse2()) unmask_sse2(); } -static void unmask_fpe_conditional(int unmasked) +static void unmask_fpe(void) { - if (unmasked) - unmask_fpe(); + __asm__ __volatile__("fnclex"); + unmask_fpe_internal(); } -/* mask x86 FPE, return true if the previous state was unmasked */ static int mask_fpe(void) { int unmasked; @@ -285,9 +292,7 @@ static int mask_fpe(void) void erts_restore_fpu(void) { __asm__ __volatile__("fninit"); - unmask_x87(); - if (cpu_has_sse2()) - unmask_sse2(); + unmask_fpe_internal(); } #elif defined(__sparc__) && defined(__linux__) @@ -310,13 +315,6 @@ static void unmask_fpe(void) __asm__ __volatile__(LDX " %0, %%fsr" : : "m"(fsr)); } -static void unmask_fpe_conditional(int unmasked) -{ - if (unmasked) - unmask_fpe(); -} - -/* mask SPARC FPE, return true if the previous state was unmasked */ static int mask_fpe(void) { unsigned long fsr; @@ -431,13 +429,6 @@ static void unmask_fpe(void) set_fpscr(0x80|0x40|0x10); /* VE, OE, ZE; not UE or XE */ } -static void unmask_fpe_conditional(int unmasked) -{ - if (unmasked) - unmask_fpe(); -} - -/* mask PowerPC FPE, return true if the previous state was unmasked */ static int mask_fpe(void) { int unmasked; @@ -447,20 +438,13 @@ static int mask_fpe(void) return unmasked; } -#else +#else /* !(x86 || (sparc && linux) || (powerpc && (linux || darwin))) */ static void unmask_fpe(void) { fpsetmask(FP_X_INV | FP_X_OFL | FP_X_DZ); } -static void unmask_fpe_conditional(int unmasked) -{ - if (unmasked) - unmask_fpe(); -} - -/* mask IEEE FPE, return true if previous state was unmasked */ static int mask_fpe(void) { const fp_except unmasked_mask = FP_X_INV | FP_X_OFL | FP_X_DZ; @@ -472,6 +456,16 @@ static int mask_fpe(void) #endif +/* + * Define a processor and OS-specific SIGFPE handler. + * + * The effect of receiving a SIGFPE should be: + * 1. Update the processor context: + * a) on x86: mask FP exceptions, do not skip faulting instruction + * b) on SPARC and PowerPC: unmask FP exceptions, skip faulting instruction + * 2. call set_current_fp_exception with the PC of the faulting instruction + */ + #if (defined(__linux__) && (defined(__i386__) || defined(__x86_64__) || defined(__sparc__) || defined(__powerpc__))) || (defined(__DARWIN__) && (defined(__i386__) || defined(__x86_64__) || defined(__ppc__))) || (defined(__FreeBSD__) && (defined(__x86_64__) || defined(__i386__))) || ((defined(__NetBSD__) || defined(__OpenBSD__)) && defined(__x86_64__)) || (defined(__sun__) && defined(__x86_64__)) #if defined(__linux__) && defined(__i386__) @@ -530,8 +524,7 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc) ucontext_t *uc = puc; unsigned long pc; -#if defined(__linux__) -#if defined(__x86_64__) +#if defined(__linux__) && defined(__x86_64__) mcontext_t *mc = &uc->uc_mcontext; fpregset_t fpstate = mc->fpregs; pc = mc_pc(mc); @@ -543,26 +536,26 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc) set encoding makes that a poor solution here. */ fpstate->mxcsr = 0x1F80; fpstate->swd &= ~0xFF; -#elif defined(__i386__) +#elif defined(__linux__) && defined(__i386__) mcontext_t *mc = &uc->uc_mcontext; fpregset_t fpstate = mc->fpregs; pc = mc_pc(mc); if ((fpstate->status >> 16) == X86_FXSR_MAGIC) ((struct _fpstate*)fpstate)->mxcsr = 0x1F80; fpstate->sw &= ~0xFF; -#elif defined(__sparc__) && defined(__arch64__) +#elif defined(__linux__) && defined(__sparc__) && defined(__arch64__) /* on SPARC the 3rd parameter points to a sigcontext not a ucontext */ struct sigcontext *sc = (struct sigcontext*)puc; pc = sc->sigc_regs.tpc; sc->sigc_regs.tpc = sc->sigc_regs.tnpc; sc->sigc_regs.tnpc += 4; -#elif defined(__sparc__) +#elif defined(__linux__) && defined(__sparc__) /* on SPARC the 3rd parameter points to a sigcontext not a ucontext */ struct sigcontext *sc = (struct sigcontext*)puc; pc = sc->si_regs.pc; sc->si_regs.pc = sc->si_regs.npc; sc->si_regs.npc = (unsigned long)sc->si_regs.npc + 4; -#elif defined(__powerpc__) +#elif defined(__linux__) && defined(__powerpc__) #if defined(__powerpc64__) mcontext_t *mc = &uc->uc_mcontext; unsigned long *regs = &mc->gp_regs[0]; @@ -573,7 +566,6 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc) pc = regs[PT_NIP]; regs[PT_NIP] += 4; regs[PT_FPSCR] = 0x80|0x40|0x10; /* VE, OE, ZE; not UE or XE */ -#endif #elif defined(__DARWIN__) && (defined(__i386__) || defined(__x86_64__)) #ifdef DARWIN_MODERN_MCONTEXT mcontext_t mc = uc->uc_mcontext; @@ -641,7 +633,7 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc) #endif #if 0 { - char buf[64]; + char buf[128]; snprintf(buf, sizeof buf, "%s: FPE at %p\r\n", __FUNCTION__, (void*)pc); write(2, buf, strlen(buf)); } @@ -726,7 +718,8 @@ int erts_sys_block_fpe(void) void erts_sys_unblock_fpe(int unmasked) { - unmask_fpe_conditional(unmasked); + if (unmasked) + unmask_fpe(); } #endif -- cgit v1.2.3