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