Implement the prctl(2) interface for IEEE Std 754 NaN interlinking, as per "MIPS ABI Extension for IEEE Std 754 Non-Compliant Interlinking" <https://dmz-portal.mips.com/wiki/MIPS_ABI_-_NaN_Interlinking>: * interpret the PR_SET_IEEE754_MODE request, * accept or reject the new mode requested according to FP hardware or emulator capabilities and any `ieee754=' kernel parameter in effect, * set the values of the FCSR ABS2008 and NAN2008 bits according to the NaN encoding requested, either PR_IEEE754_MODE_NAN_LEGACY or PR_IEEE754_MODE_NAN_2008, if writable, * on success return bits 31:24 of the auxiliary vector's AT_FLAGS value corresponding to the new mode in effect, in bits 7:0 of the result. Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxx> --- linux-mips-nan-interlink-prctl.diff Index: linux-sfr-test/arch/mips/include/asm/processor.h =================================================================== --- linux-sfr-test.orig/arch/mips/include/asm/processor.h 2015-11-11 12:34:46.131650000 +0000 +++ linux-sfr-test/arch/mips/include/asm/processor.h 2015-11-11 13:14:09.208745000 +0000 @@ -402,4 +402,13 @@ extern int mips_set_process_fp_mode(stru #define GET_FP_MODE(task) mips_get_process_fp_mode(task) #define SET_FP_MODE(task,value) mips_set_process_fp_mode(task, value) +/* + * Likewise the PR_SET_IEEE754_MODE option. + */ +extern int mips_set_process_ieee754_mode(struct task_struct *task, + unsigned int mode, unsigned int what); + +#define SET_IEEE754_MODE(task, mode, what) \ + mips_set_process_ieee754_mode((task), (mode), (what)) + #endif /* _ASM_PROCESSOR_H */ Index: linux-sfr-test/arch/mips/kernel/process.c =================================================================== --- linux-sfr-test.orig/arch/mips/kernel/process.c 2015-11-11 12:34:46.154646000 +0000 +++ linux-sfr-test/arch/mips/kernel/process.c 2015-11-11 13:17:14.564231000 +0000 @@ -9,6 +9,7 @@ * Copyright (C) 2004 Thiemo Seufer * Copyright (C) 2013 Imagination Technologies Ltd. */ +#include <linux/elf.h> #include <linux/errno.h> #include <linux/sched.h> #include <linux/tick.h> @@ -39,7 +40,6 @@ #include <asm/reg.h> #include <asm/uaccess.h> #include <asm/io.h> -#include <asm/elf.h> #include <asm/isadep.h> #include <asm/inst.h> #include <asm/stacktrace.h> @@ -682,3 +682,76 @@ int mips_set_process_fp_mode(struct task return 0; } + +/* + * Set the process's IEEE 754 compliance mode according to MODE, either + * strict or relaxed, affecting WHAT, either legacy or 2008 NaN. On + * success return an updated bit pattern as in bits 31:24 of the value + * of of of the AT_FLAGS auxiliary vector entry upon program startup, + * shifted into bits 7:0 of the result. + */ +int mips_set_process_ieee754_mode(struct task_struct *task, + unsigned int mode, unsigned int what) +{ + struct cpuinfo_mips *c = &boot_cpu_data; + struct task_struct *t; + bool nan_2008; + bool relaxed; + + switch (mode) { + case PR_IEEE754_MODE_LEGACY: + relaxed = mips_default_ieee754_relaxed; + break; + case PR_IEEE754_MODE_STRICT: + relaxed = false; + break; + case PR_IEEE754_MODE_RELAXED: + if (mips_accept_ieee754_relaxed) + relaxed = true; + else + return -EOPNOTSUPP; + break; + default: + return -EINVAL; + } + switch (what) { + case PR_IEEE754_MODE_NAN_LEGACY: + if (relaxed || mips_use_nan_legacy) + nan_2008 = false; + else + return -ENXIO; + break; + case PR_IEEE754_MODE_NAN_2008: + if (relaxed || mips_use_nan_2008) + nan_2008 = true; + else + return -ENXIO; + break; + default: + return -EINVAL; + } + + mips_get_fp_context(task); + + for_each_thread(task, t) { + if (relaxed) + set_thread_flag(TIF_IEEE754_RELAXED); + else + clear_thread_flag(TIF_IEEE754_RELAXED); + if (nan_2008) { + if (!(c->fpu_msk31 & FPU_CSR_NAN2008)) + t->thread.fpu.fcr31 |= FPU_CSR_NAN2008; + if (!(c->fpu_msk31 & FPU_CSR_ABS2008)) + t->thread.fpu.fcr31 |= FPU_CSR_ABS2008; + } else { + if (!(c->fpu_msk31 & FPU_CSR_NAN2008)) + t->thread.fpu.fcr31 &= ~FPU_CSR_NAN2008; + if (!(c->fpu_msk31 & FPU_CSR_ABS2008)) + t->thread.fpu.fcr31 &= ~FPU_CSR_ABS2008; + } + } + + mips_put_fp_context(task); + + return ELF_FLAGS >> AV_FLAGS_SYSTEM_SHIFT; +} Index: linux-sfr-test/include/uapi/linux/prctl.h =================================================================== --- linux-sfr-test.orig/include/uapi/linux/prctl.h 2015-11-11 12:34:46.157647000 +0000 +++ linux-sfr-test/include/uapi/linux/prctl.h 2015-11-11 13:14:09.286746000 +0000 @@ -197,4 +197,16 @@ struct prctl_mm_map { # define PR_CAP_AMBIENT_LOWER 3 # define PR_CAP_AMBIENT_CLEAR_ALL 4 +/* + * Control MIPS IEEE 754 compliance modes. + */ +#define PR_SET_IEEE754_MODE 48 + +# define PR_IEEE754_MODE_LEGACY 0 /* Legacy mode. */ +# define PR_IEEE754_MODE_STRICT 1 /* Strict mode. */ +# define PR_IEEE754_MODE_RELAXED 2 /* Relaxed mode. */ + +# define PR_IEEE754_MODE_NAN_LEGACY 0 /* Set legacy NaN encoding. */ +# define PR_IEEE754_MODE_NAN_2008 1 /* Set 2008 NaN encoding. */ + #endif /* _LINUX_PRCTL_H */ Index: linux-sfr-test/kernel/sys.c =================================================================== --- linux-sfr-test.orig/kernel/sys.c 2015-11-11 12:34:46.159650000 +0000 +++ linux-sfr-test/kernel/sys.c 2015-11-11 13:14:09.342744000 +0000 @@ -103,6 +103,9 @@ #ifndef SET_FP_MODE # define SET_FP_MODE(a,b) (-EINVAL) #endif +#ifndef SET_IEEE754_MODE +# define SET_IEEE754_MODE(a, b, c) (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -2266,6 +2269,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsi case PR_GET_FP_MODE: error = GET_FP_MODE(me); break; + case PR_SET_IEEE754_MODE: + error = SET_IEEE754_MODE(me, arg2, arg3); + break; default: error = -EINVAL; break;
