diff options
Diffstat (limited to 'arch/nds32/include/uapi/asm/sigcontext.h')
| -rw-r--r-- | arch/nds32/include/uapi/asm/sigcontext.h | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/arch/nds32/include/uapi/asm/sigcontext.h b/arch/nds32/include/uapi/asm/sigcontext.h index 628ff6b75825..dc89af7ddcc3 100644 --- a/arch/nds32/include/uapi/asm/sigcontext.h +++ b/arch/nds32/include/uapi/asm/sigcontext.h @@ -13,14 +13,24 @@ struct fpu_struct { unsigned long long fd_regs[32]; unsigned long fpcsr; /* - * UDF_trap is used to recognize whether underflow trap is enabled - * or not. When UDF_trap == 1, this process will be traped and then - * get a SIGFPE signal when encountering an underflow exception. - * UDF_trap is only modified through setfputrap syscall. Therefore, - * UDF_trap needn't be saved or loaded to context in each context - * switch. + * When CONFIG_SUPPORT_DENORMAL_ARITHMETIC is defined, kernel prevents + * hardware from treating the denormalized output as an underflow case + * and rounding it to a normal number. Hence kernel enables the UDF and + * IEX trap in the fpcsr register to step in the calculation. + * However, the UDF and IEX trap enable bit in $fpcsr also lose + * their use. + * + * UDF_IEX_trap replaces the feature of UDF and IEX trap enable bit in + * $fpcsr to control the trap of underflow and inexact. The bit filed + * of UDF_IEX_trap is the same as $fpcsr, 10th bit is used to enable UDF + * exception trapping and 11th bit is used to enable IEX exception + * trapping. + * + * UDF_IEX_trap is only modified through fp_udfiex_crtl syscall. + * Therefore, UDF_IEX_trap needn't be saved and restored in each + * context switch. */ - unsigned long UDF_trap; + unsigned long UDF_IEX_trap; }; struct zol_struct { |