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linux/arch/avr32/kernel/entry-avr32b.S
Haavard Skinnemoen 9e3f544d79 avr32: Fix lockup after Java stack underflow in user mode 
When using the Java Extension Module hardware, a Java stack underflow or
overflow trap may cause the system to enter an infinite exception loop.
Although there's no kernel support for the Java hardware yet, we need to
be able to recover from this situation and keep the system running.

This patch adds code to detect and fixup this situation in the critical
exception handler and terminate the faulting process. We may have to
rethink how to handle this more gracefully when the necessary kernel
support for hardware-accelerated Java is added.

Reported-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
2008-09-01 13:04:04 +02:00

875 lines
18 KiB
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/*
* Copyright (C) 2004-2006 Atmel Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/*
* This file contains the low-level entry-points into the kernel, that is,
* exception handlers, debug trap handlers, interrupt handlers and the
* system call handler.
*/
#include <linux/errno.h>
#include <asm/asm.h>
#include <asm/hardirq.h>
#include <asm/irq.h>
#include <asm/ocd.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/ptrace.h>
#include <asm/sysreg.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#ifdef CONFIG_PREEMPT
# define preempt_stop mask_interrupts
#else
# define preempt_stop
# define fault_resume_kernel fault_restore_all
#endif
#define __MASK(x) ((1 << (x)) - 1)
#define IRQ_MASK ((__MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) | \
(__MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT))
.section .ex.text,"ax",@progbits
.align 2
exception_vectors:
bral handle_critical
.align 2
bral handle_critical
.align 2
bral do_bus_error_write
.align 2
bral do_bus_error_read
.align 2
bral do_nmi_ll
.align 2
bral handle_address_fault
.align 2
bral handle_protection_fault
.align 2
bral handle_debug
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral do_fpe_ll
.align 2
bral do_illegal_opcode_ll
.align 2
bral handle_address_fault
.align 2
bral handle_address_fault
.align 2
bral handle_protection_fault
.align 2
bral handle_protection_fault
.align 2
bral do_dtlb_modified
#define tlbmiss_save pushm r0-r3
#define tlbmiss_restore popm r0-r3
.org 0x50
.global itlb_miss
itlb_miss:
tlbmiss_save
rjmp tlb_miss_common
.org 0x60
dtlb_miss_read:
tlbmiss_save
rjmp tlb_miss_common
.org 0x70
dtlb_miss_write:
tlbmiss_save
.global tlb_miss_common
.align 2
tlb_miss_common:
mfsr r0, SYSREG_TLBEAR
mfsr r1, SYSREG_PTBR
/*
* First level lookup: The PGD contains virtual pointers to
* the second-level page tables, but they may be NULL if not
* present.
*/
pgtbl_lookup:
lsr r2, r0, PGDIR_SHIFT
ld.w r3, r1[r2 << 2]
bfextu r1, r0, PAGE_SHIFT, PGDIR_SHIFT - PAGE_SHIFT
cp.w r3, 0
breq page_table_not_present
/* Second level lookup */
ld.w r2, r3[r1 << 2]
mfsr r0, SYSREG_TLBARLO
bld r2, _PAGE_BIT_PRESENT
brcc page_not_present
/* Mark the page as accessed */
sbr r2, _PAGE_BIT_ACCESSED
st.w r3[r1 << 2], r2
/* Drop software flags */
andl r2, _PAGE_FLAGS_HARDWARE_MASK & 0xffff
mtsr SYSREG_TLBELO, r2
/* Figure out which entry we want to replace */
mfsr r1, SYSREG_MMUCR
clz r2, r0
brcc 1f
mov r3, -1 /* All entries have been accessed, */
mov r2, 0 /* so start at 0 */
mtsr SYSREG_TLBARLO, r3 /* and reset TLBAR */
1: bfins r1, r2, SYSREG_DRP_OFFSET, SYSREG_DRP_SIZE
mtsr SYSREG_MMUCR, r1
tlbw
tlbmiss_restore
rete
/* The slow path of the TLB miss handler */
.align 2
page_table_not_present:
/* Do we need to synchronize with swapper_pg_dir? */
bld r0, 31
brcs sync_with_swapper_pg_dir
page_not_present:
tlbmiss_restore
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_page_fault
rjmp ret_from_exception
.align 2
sync_with_swapper_pg_dir:
/*
* If swapper_pg_dir contains a non-NULL second-level page
* table pointer, copy it into the current PGD. If not, we
* must handle it as a full-blown page fault.
*
* Jumping back to pgtbl_lookup causes an unnecessary lookup,
* but it is guaranteed to be a cache hit, it won't happen
* very often, and we absolutely do not want to sacrifice any
* performance in the fast path in order to improve this.
*/
mov r1, lo(swapper_pg_dir)
orh r1, hi(swapper_pg_dir)
ld.w r3, r1[r2 << 2]
cp.w r3, 0
breq page_not_present
mfsr r1, SYSREG_PTBR
st.w r1[r2 << 2], r3
rjmp pgtbl_lookup
/*
* We currently have two bytes left at this point until we
* crash into the system call handler...
*
* Don't worry, the assembler will let us know.
*/
/* --- System Call --- */
.org 0x100
system_call:
#ifdef CONFIG_PREEMPT
mask_interrupts
#endif
pushm r12 /* r12_orig */
stmts --sp, r0-lr
mfsr r0, SYSREG_RAR_SUP
mfsr r1, SYSREG_RSR_SUP
#ifdef CONFIG_PREEMPT
unmask_interrupts
#endif
zero_fp
stm --sp, r0-r1
/* check for syscall tracing */
get_thread_info r0
ld.w r1, r0[TI_flags]
bld r1, TIF_SYSCALL_TRACE
brcs syscall_trace_enter
syscall_trace_cont:
cp.w r8, NR_syscalls
brhs syscall_badsys
lddpc lr, syscall_table_addr
ld.w lr, lr[r8 << 2]
mov r8, r5 /* 5th argument (6th is pushed by stub) */
icall lr
.global syscall_return
syscall_return:
get_thread_info r0
mask_interrupts /* make sure we don't miss an interrupt
setting need_resched or sigpending
between sampling and the rets */
/* Store the return value so that the correct value is loaded below */
stdsp sp[REG_R12], r12
ld.w r1, r0[TI_flags]
andl r1, _TIF_ALLWORK_MASK, COH
brne syscall_exit_work
syscall_exit_cont:
popm r8-r9
mtsr SYSREG_RAR_SUP, r8
mtsr SYSREG_RSR_SUP, r9
ldmts sp++, r0-lr
sub sp, -4 /* r12_orig */
rets
.align 2
syscall_table_addr:
.long sys_call_table
syscall_badsys:
mov r12, -ENOSYS
rjmp syscall_return
.global ret_from_fork
ret_from_fork:
rcall schedule_tail
/* check for syscall tracing */
get_thread_info r0
ld.w r1, r0[TI_flags]
andl r1, _TIF_ALLWORK_MASK, COH
brne syscall_exit_work
rjmp syscall_exit_cont
syscall_trace_enter:
pushm r8-r12
rcall syscall_trace
popm r8-r12
rjmp syscall_trace_cont
syscall_exit_work:
bld r1, TIF_SYSCALL_TRACE
brcc 1f
unmask_interrupts
rcall syscall_trace
mask_interrupts
ld.w r1, r0[TI_flags]
1: bld r1, TIF_NEED_RESCHED
brcc 2f
unmask_interrupts
rcall schedule
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp 1b
2: mov r2, _TIF_SIGPENDING | _TIF_RESTORE_SIGMASK
tst r1, r2
breq 3f
unmask_interrupts
mov r12, sp
mov r11, r0
rcall do_notify_resume
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp 1b
3: bld r1, TIF_BREAKPOINT
brcc syscall_exit_cont
rjmp enter_monitor_mode
/* This function expects to find offending PC in SYSREG_RAR_EX */
.type save_full_context_ex, @function
.align 2
save_full_context_ex:
mfsr r11, SYSREG_RAR_EX
sub r9, pc, . - debug_trampoline
mfsr r8, SYSREG_RSR_EX
cp.w r9, r11
breq 3f
mov r12, r8
andh r8, (MODE_MASK >> 16), COH
brne 2f
1: pushm r11, r12 /* PC and SR */
unmask_exceptions
ret r12
2: sub r10, sp, -(FRAME_SIZE_FULL - REG_LR)
stdsp sp[4], r10 /* replace saved SP */
rjmp 1b
/*
* The debug handler set up a trampoline to make us
* automatically enter monitor mode upon return, but since
* we're saving the full context, we must assume that the
* exception handler might want to alter the return address
* and/or status register. So we need to restore the original
* context and enter monitor mode manually after the exception
* has been handled.
*/
3: get_thread_info r8
ld.w r11, r8[TI_rar_saved]
ld.w r12, r8[TI_rsr_saved]
rjmp 1b
.size save_full_context_ex, . - save_full_context_ex
/* Low-level exception handlers */
handle_critical:
/*
* AT32AP700x errata:
*
* After a Java stack overflow or underflow trap, any CPU
* memory access may cause erratic behavior. This will happen
* when the four least significant bits of the JOSP system
* register contains any value between 9 and 15 (inclusive).
*
* Possible workarounds:
* - Don't use the Java Extension Module
* - Ensure that the stack overflow and underflow trap
* handlers do not do any memory access or trigger any
* exceptions before the overflow/underflow condition is
* cleared (by incrementing or decrementing the JOSP)
* - Make sure that JOSP does not contain any problematic
* value before doing any exception or interrupt
* processing.
* - Set up a critical exception handler which writes a
* known-to-be-safe value, e.g. 4, to JOSP before doing
* any further processing.
*
* We'll use the last workaround for now since we cannot
* guarantee that user space processes don't use Java mode.
* Non-well-behaving userland will be terminated with extreme
* prejudice.
*/
#ifdef CONFIG_CPU_AT32AP700X
/*
* There's a chance we can't touch memory, so temporarily
* borrow PTBR to save the stack pointer while we fix things
* up...
*/
mtsr SYSREG_PTBR, sp
mov sp, 4
mtsr SYSREG_JOSP, sp
mfsr sp, SYSREG_PTBR
sub pc, -2
/* Push most of pt_regs on stack. We'll do the rest later */
sub sp, 4
pushm r0-r12
/* PTBR mirrors current_thread_info()->task->active_mm->pgd */
get_thread_info r0
ld.w r1, r0[TI_task]
ld.w r2, r1[TSK_active_mm]
ld.w r3, r2[MM_pgd]
mtsr SYSREG_PTBR, r3
#else
sub sp, 4
pushm r0-r12
#endif
sub r0, sp, -(14 * 4)
mov r1, lr
mfsr r2, SYSREG_RAR_EX
mfsr r3, SYSREG_RSR_EX
pushm r0-r3
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_critical_exception
/* We should never get here... */
bad_return:
sub r12, pc, (. - 1f)
bral panic
.align 2
1: .asciz "Return from critical exception!"
.align 1
do_bus_error_write:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mov r11, 1
rjmp 1f
do_bus_error_read:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mov r11, 0
1: mfsr r12, SYSREG_BEAR
mov r10, sp
rcall do_bus_error
rjmp ret_from_exception
.align 1
do_nmi_ll:
sub sp, 4
stmts --sp, r0-lr
mfsr r9, SYSREG_RSR_NMI
mfsr r8, SYSREG_RAR_NMI
bfextu r0, r9, MODE_SHIFT, 3
brne 2f
1: pushm r8, r9 /* PC and SR */
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_nmi
popm r8-r9
mtsr SYSREG_RAR_NMI, r8
tst r0, r0
mtsr SYSREG_RSR_NMI, r9
brne 3f
ldmts sp++, r0-lr
sub sp, -4 /* skip r12_orig */
rete
2: sub r10, sp, -(FRAME_SIZE_FULL - REG_LR)
stdsp sp[4], r10 /* replace saved SP */
rjmp 1b
3: popm lr
sub sp, -4 /* skip sp */
popm r0-r12
sub sp, -4 /* skip r12_orig */
rete
handle_address_fault:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_address_exception
rjmp ret_from_exception
handle_protection_fault:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_page_fault
rjmp ret_from_exception
.align 1
do_illegal_opcode_ll:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_illegal_opcode
rjmp ret_from_exception
do_dtlb_modified:
pushm r0-r3
mfsr r1, SYSREG_TLBEAR
mfsr r0, SYSREG_PTBR
lsr r2, r1, PGDIR_SHIFT
ld.w r0, r0[r2 << 2]
lsl r1, (32 - PGDIR_SHIFT)
lsr r1, (32 - PGDIR_SHIFT) + PAGE_SHIFT
/* Translate to virtual address in P1 */
andl r0, 0xf000
sbr r0, 31
add r2, r0, r1 << 2
ld.w r3, r2[0]
sbr r3, _PAGE_BIT_DIRTY
mov r0, r3
st.w r2[0], r3
/* The page table is up-to-date. Update the TLB entry as well */
andl r0, lo(_PAGE_FLAGS_HARDWARE_MASK)
mtsr SYSREG_TLBELO, r0
/* MMUCR[DRP] is updated automatically, so let's go... */
tlbw
popm r0-r3
rete
do_fpe_ll:
sub sp, 4
stmts --sp, r0-lr
rcall save_full_context_ex
unmask_interrupts
mov r12, 26
mov r11, sp
rcall do_fpe
rjmp ret_from_exception
ret_from_exception:
mask_interrupts
lddsp r4, sp[REG_SR]
andh r4, (MODE_MASK >> 16), COH
brne fault_resume_kernel
get_thread_info r0
ld.w r1, r0[TI_flags]
andl r1, _TIF_WORK_MASK, COH
brne fault_exit_work
fault_resume_user:
popm r8-r9
mask_exceptions
mtsr SYSREG_RAR_EX, r8
mtsr SYSREG_RSR_EX, r9
ldmts sp++, r0-lr
sub sp, -4
rete
fault_resume_kernel:
#ifdef CONFIG_PREEMPT
get_thread_info r0
ld.w r2, r0[TI_preempt_count]
cp.w r2, 0
brne 1f
ld.w r1, r0[TI_flags]
bld r1, TIF_NEED_RESCHED
brcc 1f
lddsp r4, sp[REG_SR]
bld r4, SYSREG_GM_OFFSET
brcs 1f
rcall preempt_schedule_irq
1:
#endif
popm r8-r9
mask_exceptions
mfsr r1, SYSREG_SR
mtsr SYSREG_RAR_EX, r8
mtsr SYSREG_RSR_EX, r9
popm lr
sub sp, -4 /* ignore SP */
popm r0-r12
sub sp, -4 /* ignore r12_orig */
rete
irq_exit_work:
/* Switch to exception mode so that we can share the same code. */
mfsr r8, SYSREG_SR
cbr r8, SYSREG_M0_OFFSET
orh r8, hi(SYSREG_BIT(M1) | SYSREG_BIT(M2))
mtsr SYSREG_SR, r8
sub pc, -2
get_thread_info r0
ld.w r1, r0[TI_flags]
fault_exit_work:
bld r1, TIF_NEED_RESCHED
brcc 1f
unmask_interrupts
rcall schedule
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp fault_exit_work
1: mov r2, _TIF_SIGPENDING | _TIF_RESTORE_SIGMASK
tst r1, r2
breq 2f
unmask_interrupts
mov r12, sp
mov r11, r0
rcall do_notify_resume
mask_interrupts
ld.w r1, r0[TI_flags]
rjmp fault_exit_work
2: bld r1, TIF_BREAKPOINT
brcc fault_resume_user
rjmp enter_monitor_mode
.section .kprobes.text, "ax", @progbits
.type handle_debug, @function
handle_debug:
sub sp, 4 /* r12_orig */
stmts --sp, r0-lr
mfsr r8, SYSREG_RAR_DBG
mfsr r9, SYSREG_RSR_DBG
unmask_exceptions
pushm r8-r9
bfextu r9, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
brne debug_fixup_regs
.Ldebug_fixup_cont:
#ifdef CONFIG_TRACE_IRQFLAGS
rcall trace_hardirqs_off
#endif
mov r12, sp
rcall do_debug
mov sp, r12
lddsp r2, sp[REG_SR]
bfextu r3, r2, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
brne debug_resume_kernel
get_thread_info r0
ld.w r1, r0[TI_flags]
mov r2, _TIF_DBGWORK_MASK
tst r1, r2
brne debug_exit_work
bld r1, TIF_SINGLE_STEP
brcc 1f
mfdr r4, OCD_DC
sbr r4, OCD_DC_SS_BIT
mtdr OCD_DC, r4
1: popm r10,r11
mask_exceptions
mtsr SYSREG_RSR_DBG, r11
mtsr SYSREG_RAR_DBG, r10
#ifdef CONFIG_TRACE_IRQFLAGS
rcall trace_hardirqs_on
1:
#endif
ldmts sp++, r0-lr
sub sp, -4
retd
.size handle_debug, . - handle_debug
/* Mode of the trapped context is in r9 */
.type debug_fixup_regs, @function
debug_fixup_regs:
mfsr r8, SYSREG_SR
mov r10, r8
bfins r8, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
mtsr SYSREG_SR, r8
sub pc, -2
stdsp sp[REG_LR], lr
mtsr SYSREG_SR, r10
sub pc, -2
sub r8, sp, -FRAME_SIZE_FULL
stdsp sp[REG_SP], r8
rjmp .Ldebug_fixup_cont
.size debug_fixup_regs, . - debug_fixup_regs
.type debug_resume_kernel, @function
debug_resume_kernel:
mask_exceptions
popm r10, r11
mtsr SYSREG_RAR_DBG, r10
mtsr SYSREG_RSR_DBG, r11
#ifdef CONFIG_TRACE_IRQFLAGS
bld r11, SYSREG_GM_OFFSET
brcc 1f
rcall trace_hardirqs_on
1:
#endif
mfsr r2, SYSREG_SR
mov r1, r2
bfins r2, r3, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
mtsr SYSREG_SR, r2
sub pc, -2
popm lr
mtsr SYSREG_SR, r1
sub pc, -2
sub sp, -4 /* skip SP */
popm r0-r12
sub sp, -4
retd
.size debug_resume_kernel, . - debug_resume_kernel
.type debug_exit_work, @function
debug_exit_work:
/*
* We must return from Monitor Mode using a retd, and we must
* not schedule since that involves the D bit in SR getting
* cleared by something other than the debug hardware. This
* may cause undefined behaviour according to the Architecture
* manual.
*
* So we fix up the return address and status and return to a
* stub below in Exception mode. From there, we can follow the
* normal exception return path.
*
* The real return address and status registers are stored on
* the stack in the way the exception return path understands,
* so no need to fix anything up there.
*/
sub r8, pc, . - fault_exit_work
mtsr SYSREG_RAR_DBG, r8
mov r9, 0
orh r9, hi(SR_EM | SR_GM | MODE_EXCEPTION)
mtsr SYSREG_RSR_DBG, r9
sub pc, -2
retd
.size debug_exit_work, . - debug_exit_work
.set rsr_int0, SYSREG_RSR_INT0
.set rsr_int1, SYSREG_RSR_INT1
.set rsr_int2, SYSREG_RSR_INT2
.set rsr_int3, SYSREG_RSR_INT3
.set rar_int0, SYSREG_RAR_INT0
.set rar_int1, SYSREG_RAR_INT1
.set rar_int2, SYSREG_RAR_INT2
.set rar_int3, SYSREG_RAR_INT3
.macro IRQ_LEVEL level
.type irq_level\level, @function
irq_level\level:
sub sp, 4 /* r12_orig */
stmts --sp,r0-lr
mfsr r8, rar_int\level
mfsr r9, rsr_int\level
#ifdef CONFIG_PREEMPT
sub r11, pc, (. - system_call)
cp.w r11, r8
breq 4f
#endif
pushm r8-r9
mov r11, sp
mov r12, \level
rcall do_IRQ
lddsp r4, sp[REG_SR]
bfextu r4, r4, SYSREG_M0_OFFSET, 3
cp.w r4, MODE_SUPERVISOR >> SYSREG_M0_OFFSET
breq 2f
cp.w r4, MODE_USER >> SYSREG_M0_OFFSET
#ifdef CONFIG_PREEMPT
brne 3f
#else
brne 1f
#endif
get_thread_info r0
ld.w r1, r0[TI_flags]
andl r1, _TIF_WORK_MASK, COH
brne irq_exit_work
1:
#ifdef CONFIG_TRACE_IRQFLAGS
rcall trace_hardirqs_on
#endif
popm r8-r9
mtsr rar_int\level, r8
mtsr rsr_int\level, r9
ldmts sp++,r0-lr
sub sp, -4 /* ignore r12_orig */
rete
#ifdef CONFIG_PREEMPT
4: mask_interrupts
mfsr r8, rsr_int\level
sbr r8, 16
mtsr rsr_int\level, r8
ldmts sp++, r0-lr
sub sp, -4 /* ignore r12_orig */
rete
#endif
2: get_thread_info r0
ld.w r1, r0[TI_flags]
bld r1, TIF_CPU_GOING_TO_SLEEP
#ifdef CONFIG_PREEMPT
brcc 3f
#else
brcc 1b
#endif
sub r1, pc, . - cpu_idle_skip_sleep
stdsp sp[REG_PC], r1
#ifdef CONFIG_PREEMPT
3: get_thread_info r0
ld.w r2, r0[TI_preempt_count]
cp.w r2, 0
brne 1b
ld.w r1, r0[TI_flags]
bld r1, TIF_NEED_RESCHED
brcc 1b
lddsp r4, sp[REG_SR]
bld r4, SYSREG_GM_OFFSET
brcs 1b
rcall preempt_schedule_irq
#endif
rjmp 1b
.endm
.section .irq.text,"ax",@progbits
.global irq_level0
.global irq_level1
.global irq_level2
.global irq_level3
IRQ_LEVEL 0
IRQ_LEVEL 1
IRQ_LEVEL 2
IRQ_LEVEL 3
.section .kprobes.text, "ax", @progbits
.type enter_monitor_mode, @function
enter_monitor_mode:
/*
* We need to enter monitor mode to do a single step. The
* monitor code will alter the return address so that we
* return directly to the user instead of returning here.
*/
breakpoint
rjmp breakpoint_failed
.size enter_monitor_mode, . - enter_monitor_mode
.type debug_trampoline, @function
.global debug_trampoline
debug_trampoline:
/*
* Save the registers on the stack so that the monitor code
* can find them easily.
*/
sub sp, 4 /* r12_orig */
stmts --sp, r0-lr
get_thread_info r0
ld.w r8, r0[TI_rar_saved]
ld.w r9, r0[TI_rsr_saved]
pushm r8-r9
/*
* The monitor code will alter the return address so we don't
* return here.
*/
breakpoint
rjmp breakpoint_failed
.size debug_trampoline, . - debug_trampoline
.type breakpoint_failed, @function
breakpoint_failed:
/*
* Something went wrong. Perhaps the debug hardware isn't
* enabled?
*/
lda.w r12, msg_breakpoint_failed
mov r11, sp
mov r10, 9 /* SIGKILL */
call die
1: rjmp 1b
msg_breakpoint_failed:
.asciz "Failed to enter Debug Mode"
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