xref: /linux/arch/arm/include/asm/kgdb.h (revision 3eb66e91a25497065c5322b1268cbc3953642227)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * ARM KGDB support
4  *
5  * Author: Deepak Saxena <dsaxena@mvista.com>
6  *
7  * Copyright (C) 2002 MontaVista Software Inc.
8  *
9  */
10 
11 #ifndef __ARM_KGDB_H__
12 #define __ARM_KGDB_H__
13 
14 #include <linux/ptrace.h>
15 #include <asm/opcodes.h>
16 
17 /*
18  * GDB assumes that we're a user process being debugged, so
19  * it will send us an SWI command to write into memory as the
20  * debug trap. When an SWI occurs, the next instruction addr is
21  * placed into R14_svc before jumping to the vector trap.
22  * This doesn't work for kernel debugging as we are already in SVC
23  * we would loose the kernel's LR, which is a bad thing. This
24  * is  bad thing.
25  *
26  * By doing this as an undefined instruction trap, we force a mode
27  * switch from SVC to UND mode, allowing us to save full kernel state.
28  *
29  * We also define a KGDB_COMPILED_BREAK which can be used to compile
30  * in breakpoints. This is important for things like sysrq-G and for
31  * the initial breakpoint from trap_init().
32  *
33  * Note to ARM HW designers: Add real trap support like SH && PPC to
34  * make our lives much much simpler. :)
35  */
36 #define BREAK_INSTR_SIZE	4
37 #define GDB_BREAKINST		0xef9f0001
38 #define KGDB_BREAKINST		0xe7ffdefe
39 #define KGDB_COMPILED_BREAK	0xe7ffdeff
40 #define CACHE_FLUSH_IS_SAFE	1
41 
42 #ifndef	__ASSEMBLY__
43 
arch_kgdb_breakpoint(void)44 static inline void arch_kgdb_breakpoint(void)
45 {
46 	asm(__inst_arm(0xe7ffdeff));
47 }
48 
49 extern void kgdb_handle_bus_error(void);
50 extern int kgdb_fault_expected;
51 
52 #endif /* !__ASSEMBLY__ */
53 
54 /*
55  * From Kevin Hilman:
56  *
57  * gdb is expecting the following registers layout.
58  *
59  * r0-r15: 1 long word each
60  * f0-f7:  unused, 3 long words each !!
61  * fps:    unused, 1 long word
62  * cpsr:   1 long word
63  *
64  * Even though f0-f7 and fps are not used, they need to be
65  * present in the registers sent for correct processing in
66  * the host-side gdb.
67  *
68  * In particular, it is crucial that CPSR is in the right place,
69  * otherwise gdb will not be able to correctly interpret stepping over
70  * conditional branches.
71  */
72 #define _GP_REGS		16
73 #define _FP_REGS		8
74 #define _EXTRA_REGS		2
75 #define GDB_MAX_REGS		(_GP_REGS + (_FP_REGS * 3) + _EXTRA_REGS)
76 #define DBG_MAX_REG_NUM		(_GP_REGS + _FP_REGS + _EXTRA_REGS)
77 
78 #define KGDB_MAX_NO_CPUS	1
79 #define BUFMAX			400
80 #define NUMREGBYTES		(GDB_MAX_REGS << 2)
81 #define NUMCRITREGBYTES		(32 << 2)
82 
83 #define _R0			0
84 #define _R1			1
85 #define _R2			2
86 #define _R3			3
87 #define _R4			4
88 #define _R5			5
89 #define _R6			6
90 #define _R7			7
91 #define _R8			8
92 #define _R9			9
93 #define _R10			10
94 #define _FP			11
95 #define _IP			12
96 #define _SPT			13
97 #define _LR			14
98 #define _PC			15
99 #define _CPSR			(GDB_MAX_REGS - 1)
100 
101 /*
102  * So that we can denote the end of a frame for tracing,
103  * in the simple case:
104  */
105 #define CFI_END_FRAME(func)	__CFI_END_FRAME(_PC, _SPT, func)
106 
107 #endif /* __ASM_KGDB_H__ */
108