5141c46c61
Emulate single stepping in KGDB on MN10300 by way of temporary breakpoint insertion. These breakpoints are never actually seen by KGDB, and will overlay KGDB's own breakpoints. The breakpoints are removed by switch_to() and reinstalled on switching back so that if preemption occurs, the preempting task doesn't hit them (though it will still hit KGDB's regular breakpoints). If KGDB is reentered for any reason, then the single step breakpoint is completely erased and must be set again by the debugger. We take advantage of the fact that KGDB will effectively halt all other CPUs whilst this CPU is single-stepping to avoid SMP problems. If the single-stepping task is preempted and killed without KGDB being reinvoked, then the breakpoint(s) will be cleared and KGDB will be jumped back into. Signed-off-by: David Howells <dhowells@redhat.com>
179 lines
4 KiB
ArmAsm
179 lines
4 KiB
ArmAsm
###############################################################################
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#
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# MN10300 Context switch operation
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#
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# Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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# Written by David Howells (dhowells@redhat.com)
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public Licence
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# as published by the Free Software Foundation; either version
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# 2 of the Licence, or (at your option) any later version.
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#
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###############################################################################
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#include <linux/sys.h>
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#include <linux/linkage.h>
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#include <asm/thread_info.h>
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#include <asm/cpu-regs.h>
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#ifdef CONFIG_SMP
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#include <proc/smp-regs.h>
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#endif /* CONFIG_SMP */
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.text
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###############################################################################
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#
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# struct task_struct *__switch_to(struct thread_struct *prev,
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# struct thread_struct *next,
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# struct task_struct *prev_task)
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#
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###############################################################################
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ENTRY(__switch_to)
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movm [d2,d3,a2,a3,exreg1],(sp)
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or EPSW_NMID,epsw
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mov (44,sp),d2
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mov d0,a0
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mov d1,a1
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# save prev context
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mov __switch_back,d0
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mov sp,a2
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mov a2,(THREAD_SP,a0)
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mov a3,(THREAD_A3,a0)
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#ifdef CONFIG_KGDB
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btst 0xff,(kgdb_single_step)
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bne __switch_to__lift_sstep_bp
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__switch_to__continue:
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#endif
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mov d0,(THREAD_PC,a0)
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mov (THREAD_A3,a1),a3
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mov (THREAD_SP,a1),a2
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# switch
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mov a2,sp
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# load next context
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GET_THREAD_INFO a2
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mov a2,(__current_ti)
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mov (TI_task,a2),a2
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mov a2,(__current)
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#ifdef CONFIG_MN10300_CURRENT_IN_E2
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mov a2,e2
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#endif
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mov (THREAD_PC,a1),a2
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mov d2,d0 # for ret_from_fork
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mov d0,a0 # for __switch_to
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jmp (a2)
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__switch_back:
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and ~EPSW_NMID,epsw
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ret [d2,d3,a2,a3,exreg1],32
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#ifdef CONFIG_KGDB
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###############################################################################
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#
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# Lift the single-step breakpoints when the task being traced is switched out
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# A0 = prev
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# A1 = next
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#
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###############################################################################
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__switch_to__lift_sstep_bp:
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add -12,sp
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mov a0,e4
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mov a1,e5
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# Clear the single-step flag to prevent us coming this way until we get
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# switched back in
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bclr 0xff,(kgdb_single_step)
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# Remove first breakpoint
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mov (kgdb_sstep_bp_addr),a2
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cmp 0,a2
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beq 1f
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movbu (kgdb_sstep_bp),d0
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movbu d0,(a2)
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#if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
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mov a2,d0
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mov a2,d1
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add 1,d1
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calls flush_icache_range
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#endif
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1:
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# Remove second breakpoint
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mov (kgdb_sstep_bp_addr+4),a2
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cmp 0,a2
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beq 2f
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movbu (kgdb_sstep_bp+1),d0
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movbu d0,(a2)
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#if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
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mov a2,d0
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mov a2,d1
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add 1,d1
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calls flush_icache_range
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#endif
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2:
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# Change the resumption address and return
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mov __switch_back__reinstall_sstep_bp,d0
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mov e4,a0
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mov e5,a1
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add 12,sp
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bra __switch_to__continue
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###############################################################################
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#
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# Reinstall the single-step breakpoints when the task being traced is switched
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# back in (A1 points to the new thread_struct).
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#
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###############################################################################
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__switch_back__reinstall_sstep_bp:
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add -12,sp
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mov a0,e4 # save the return value
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mov 0xff,d3
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# Reinstall first breakpoint
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mov (kgdb_sstep_bp_addr),a2
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cmp 0,a2
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beq 1f
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movbu (a2),d0
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movbu d0,(kgdb_sstep_bp)
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movbu d3,(a2)
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#if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
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mov a2,d0
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mov a2,d1
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add 1,d1
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calls flush_icache_range
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#endif
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1:
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# Reinstall second breakpoint
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mov (kgdb_sstep_bp_addr+4),a2
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cmp 0,a2
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beq 2f
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movbu (a2),d0
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movbu d0,(kgdb_sstep_bp+1)
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movbu d3,(a2)
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#if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
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mov a2,d0
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mov a2,d1
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add 1,d1
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calls flush_icache_range
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#endif
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2:
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mov d3,(kgdb_single_step)
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# Restore the return value (the previous thread_struct pointer)
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mov e4,a0
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mov a0,d0
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add 12,sp
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bra __switch_back
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#endif /* CONFIG_KGDB */
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