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introduce a inline function to set a value to zero while 

hiding this fact from GCC.  this allows the PPC code that
writes to address zero to actually work rather than cause
GCC to emit an explicit "trap" instruction, which in early
boot means hang on my pegasosII.  use this in oae_init()
for both rfid->rfi and also setting the jump-to-zero trap.

found with a lot of debugging, but GCC 6's new warning
-Wnull-dereference found it when i was informed of its
existence.  unfortunately, there are dozens of other
violations in our kernel today so simply enabling that
option for everything is not a good idea, but is a goal.
This commit is contained in:
mrg 2018-02-11 00:01:12 +00:00
parent e8b7cd3e82
commit 3752203969
1 changed files with 20 additions and 5 deletions
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25
sys/arch/powerpc/oea/oea_machdep.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: oea_machdep.c,v 1.73 2016/05/30 13:04:24 chs Exp $ */
/* $NetBSD: oea_machdep.c,v 1.74 2018/02/11 00:01:12 mrg Exp $ */
/*
* Copyright (C) 2002 Matt Thomas
@ -33,7 +33,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: oea_machdep.c,v 1.73 2016/05/30 13:04:24 chs Exp $");
__KERNEL_RCSID(0, "$NetBSD: oea_machdep.c,v 1.74 2018/02/11 00:01:12 mrg Exp $");
#include "opt_ppcarch.h"
#include "opt_compat_netbsd.h"
@ -109,6 +109,19 @@ extern int dsitrap_fix_dbat5[];
extern int dsitrap_fix_dbat6[];
extern int dsitrap_fix_dbat7[];
/*
* Load pointer with 0 behind GCC's back, otherwise it will
* emit a "trap" instead.
*/
static __inline__ uintptr_t
zero_value(void)
{
uintptr_t dont_tell_gcc;
__asm volatile ("li %0, 0" : "=r"(dont_tell_gcc) :);
return dont_tell_gcc;
}
void
oea_init(void (*handler)(void))
{
@ -144,7 +157,7 @@ oea_init(void (*handler)(void))
#ifdef PPC_HIGH_VEC
exc_base = EXC_HIGHVEC;
#else
exc_base = 0;
exc_base = zero_value();
#endif
KASSERT(mfspr(SPR_SPRG0) == (uintptr_t)ci);
@ -289,8 +302,10 @@ oea_init(void (*handler)(void))
* Install a branch absolute to trap0 to force a panic.
*/
if ((uintptr_t)trap0 < 0x2000000) {
*(volatile uint32_t *) 0 = 0x7c6802a6;
*(volatile uint32_t *) 4 = 0x48000002 | (uintptr_t) trap0;
uint32_t *p = (uint32_t *)zero_value();
p[0] = 0x7c6802a6;
p[1] = 0x48000002 | (uintptr_t) trap0;
}
/*