1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * AArch64 KGDB support
4 *
5 * Based on arch/arm/include/kgdb.h
6 *
7 * Copyright (C) 2013 Cavium Inc.
8 * Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
9 */
10
11 #ifndef __ARM_KGDB_H
12 #define __ARM_KGDB_H
13
14 #include <linux/ptrace.h>
15 #include <asm/debug-monitors.h>
16
17 #ifndef __ASSEMBLY__
18
19 static inline void arch_kgdb_breakpoint(void)
20 {
21 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM));
22 }
23
24 extern void kgdb_handle_bus_error(void);
25 extern int kgdb_fault_expected;
26
27 #endif /* !__ASSEMBLY__ */
28
29 /*
30 * gdb remote procotol (well most versions of it) expects the following
31 * register layout.
32 *
33 * General purpose regs:
34 * r0-r30: 64 bit
35 * sp,pc : 64 bit
36 * pstate : 32 bit
37 * Total: 33 + 1
38 * FPU regs:
39 * f0-f31: 128 bit
40 * fpsr & fpcr: 32 bit
41 * Total: 32 + 2
42 *
43 * To expand a little on the "most versions of it"... when the gdb remote
44 * protocol for AArch64 was developed it depended on a statement in the
45 * Architecture Reference Manual that claimed "SPSR_ELx is a 32-bit register".
46 * and, as a result, allocated only 32-bits for the PSTATE in the remote
47 * protocol. In fact this statement is still present in ARM DDI 0487A.i.
48 *
49 * Unfortunately "is a 32-bit register" has a very special meaning for
50 * system registers. It means that "the upper bits, bits[63:32], are
51 * RES0.". RES0 is heavily used in the ARM architecture documents as a
52 * way to leave space for future architecture changes. So to translate a
53 * little for people who don't spend their spare time reading ARM architecture
54 * manuals, what "is a 32-bit register" actually means in this context is
55 * "is a 64-bit register but one with no meaning allocated to any of the
56 * upper 32-bits... *yet*".
57 *
58 * Perhaps then we should not be surprised that this has led to some
59 * confusion. Specifically a patch, influenced by the above translation,
60 * that extended PSTATE to 64-bit was accepted into gdb-7.7 but the patch
61 * was reverted in gdb-7.8.1 and all later releases, when this was
62 * discovered to be an undocumented protocol change.
63 *
64 * So... it is *not* wrong for us to only allocate 32-bits to PSTATE
65 * here even though the kernel itself allocates 64-bits for the same
66 * state. That is because this bit of code tells the kernel how the gdb
67 * remote protocol (well most versions of it) describes the register state.
68 *
69 * Note that if you are using one of the versions of gdb that supports
70 * the gdb-7.7 version of the protocol you cannot use kgdb directly
71 * without providing a custom register description (gdb can load new
72 * protocol descriptions at runtime).
73 */
74
75 #define _GP_REGS 33
76 #define _FP_REGS 32
77 #define _EXTRA_REGS 3
78 /*
79 * general purpose registers size in bytes.
80 * pstate is only 4 bytes. subtract 4 bytes
81 */
82 #define GP_REG_BYTES (_GP_REGS * 8)
83 #define DBG_MAX_REG_NUM (_GP_REGS + _FP_REGS + _EXTRA_REGS)
84
85 /*
86 * Size of I/O buffer for gdb packet.
87 * considering to hold all register contents, size is set
88 */
89
90 #define BUFMAX 2048
91
92 /*
93 * Number of bytes required for gdb_regs buffer.
94 * _GP_REGS: 8 bytes, _FP_REGS: 16 bytes and _EXTRA_REGS: 4 bytes each
95 * GDB fails to connect for size beyond this with error
96 * "'g' packet reply is too long"
97 */
98
99 #define NUMREGBYTES ((_GP_REGS * 8) + (_FP_REGS * 16) + \
100 (_EXTRA_REGS * 4))
101
102 #endif /* __ASM_KGDB_H */