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Add what I hope is a useful feature whereby, in DIAGNOSTIC builds, trap 

handlers leave a useful sentinel value in R14_svc instead of their own
return address.  This should mean that if something causes a trap in SVC
mode without saving R14 first, it'll cause a nice obvious panic rather than
a hang or worse.  Of course, if it's using R14 as a temporary, there may
still be some confusion.
This commit is contained in:
bjh21 2009-01-18 15:14:34 +00:00
parent 39c9db5df2
commit 30286df7bb
1 changed files with 33 additions and 2 deletions
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35
sys/arch/acorn26/acorn26/locore.S
View File

@ -1,4 +1,4 @@
/* $NetBSD: locore.S,v 1.19 2009/01/18 01:30:44 bjh21 Exp $ */ /* $NetBSD: locore.S,v 1.20 2009/01/18 15:14:34 bjh21 Exp $ */
/* /*
* Copyright (c) 1998, 1999, 2000 Ben Harris * Copyright (c) 1998, 1999, 2000 Ben Harris
* Copyright (C) 1994-1997 Mark Brinicombe * Copyright (C) 1994-1997 Mark Brinicombe
@ -175,6 +175,7 @@ pull_trapframe:
bl _C_LABEL(ast) /* Handle AST */ bl _C_LABEL(ast) /* Handle AST */
b 1b /* Try again */ b 1b /* Try again */
#ifndef DIAGNOSTIC
2: 2:
ldr lr, [sp, #TF_R15] /* Pull return address */ ldr lr, [sp, #TF_R15] /* Pull return address */
3: /* ... which we may have done above */ 3: /* ... which we may have done above */
@ -183,6 +184,36 @@ pull_trapframe:
USR_LDM_NOP USR_LDM_NOP
add sp, sp, #(TF_SIZE-TF_R0) /* Adjust SP */ add sp, sp, #(TF_SIZE-TF_R0) /* Adjust SP */
movs pc, lr movs pc, lr
#else /* DIAGNOSTIC */
/*
* Taking a trap inherently corrupts R14_svc. Rather than leaving
* it with the return address in, we put in a sentinel value that'll
* panic if it's treated as a return address. To do this, we have
* to return via IRQ mode.
*/
2:
3:
adr lr, r14_svc_corrupted /* Sentinel in R14_svc */
mov r0, sp /* Save for mode switch */
add sp, sp, #TF_SIZE /* Restore stack pointer */
teqp r15, #(R15_IRQ_DISABLE | R15_MODE_IRQ)
add r0, r0, #TF_R0
ldr lr, [r0, #(TF_R15-TF_R0)] /* Fetch return address (R14_irq) */
ldmia r0, {TRAP_REGS}^ /* Restore USR mode registers */
USR_LDM_NOP
movs pc, lr /* And return */
r14_svc_corrupted:
mov ip, sp
stmfd sp!, {fp, ip, lr, pc}
sub fp, ip, #4
adr r0, .Lr14_panicmsg
bl _C_LABEL(panic)
/* NOTREACHED */
.Lr14_panicmsg:
.asciz "R14_svc corrupted by trap handler"
.balign 4
#endif
.global reset_entry .global reset_entry
reset_entry: reset_entry:
@ -421,4 +452,4 @@ ENTRY(cpu_Debugger)
ldmfd r13!, {pc} ldmfd r13!, {pc}
#endif #endif
RCSID("$NetBSD: locore.S,v 1.19 2009/01/18 01:30:44 bjh21 Exp $") RCSID("$NetBSD: locore.S,v 1.20 2009/01/18 15:14:34 bjh21 Exp $")