Hi Matt, On Tue, Mar 31, 2015 at 01:30:50AM +0000, Matt Thomas wrote: > When the cpu gets an exception from kernel mode, the sscratch register will be > 0 and curlwp will be in the "tp" register. When the cpu gets an exception > from > user mode, the sscratch register will be a pointer to the current lwp.
Will the kernel not be confused and choose the wrong path if a userland programs clears the "sp" register and gets an exception, say be storing a stack frame? by accident or deliberately? > Index: src/sys/arch/riscv/riscv/locore.S > diff -u src/sys/arch/riscv/riscv/locore.S:1.1 > src/sys/arch/riscv/riscv/locore.S:1.2 > --- src/sys/arch/riscv/riscv/locore.S:1.1 Sat Mar 28 16:13:56 2015 > +++ src/sys/arch/riscv/riscv/locore.S Tue Mar 31 01:30:50 2015 > @@ -1,4 +1,4 @@ > -/* $NetBSD: locore.S,v 1.1 2015/03/28 16:13:56 matt Exp $ */ > +/* $NetBSD: locore.S,v 1.2 2015/03/31 01:30:50 matt Exp $ */ > /*- > * Copyright (c) 2014 The NetBSD Foundation, Inc. > * All rights reserved. > @@ -78,10 +78,10 @@ ENTRY_NP(start) > call memset // zero through kernel_end > > // As a temporary hack, word 0 contains the amount of memory in MB > - lw a7, (zero) // load memory size > + INT_L a7, (zero) // load memory size > slli a7, a7, (20-PGSHIFT) // convert MB to pages > - auipc t0, %pcrel_hi(physmem) > - sw a7, %pcrel_lo(physmem)(t0) // store it in physmem > +.L01: auipc t0, %pcrel_hi(physmem) > + INT_S a7, %pcrel_lo(.L01)(t0) // store it in physmem Why are you loading the lower PC relative part of .L01 in stead of physmem? won't that give the wrong lower bits? Isn't there a PTR_S macro to handle this? With regards, Reinoud
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