1/* 2 * AArch64 KGDB support 3 * 4 * Based on arch/arm/include/kgdb.h 5 * 6 * Copyright (C) 2013 Cavium Inc. 7 * Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com> 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License version 2 as 11 * published by the Free Software Foundation. 12 * 13 * This program is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU General Public License for more details. 17 * 18 * You should have received a copy of the GNU General Public License 19 * along with this program. If not, see <http://www.gnu.org/licenses/>. 20 */ 21 22#ifndef __ARM_KGDB_H 23#define __ARM_KGDB_H 24 25#include <linux/ptrace.h> 26#include <asm/debug-monitors.h> 27 28#ifndef __ASSEMBLY__ 29 30static inline void arch_kgdb_breakpoint(void) 31{ 32 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM)); 33} 34 35extern void kgdb_handle_bus_error(void); 36extern int kgdb_fault_expected; 37 38#endif /* !__ASSEMBLY__ */ 39 40/* 41 * gdb remote procotol (well most versions of it) expects the following 42 * register layout. 43 * 44 * General purpose regs: 45 * r0-r30: 64 bit 46 * sp,pc : 64 bit 47 * pstate : 32 bit 48 * Total: 33 + 1 49 * FPU regs: 50 * f0-f31: 128 bit 51 * fpsr & fpcr: 32 bit 52 * Total: 32 + 2 53 * 54 * To expand a little on the "most versions of it"... when the gdb remote 55 * protocol for AArch64 was developed it depended on a statement in the 56 * Architecture Reference Manual that claimed "SPSR_ELx is a 32-bit register". 57 * and, as a result, allocated only 32-bits for the PSTATE in the remote 58 * protocol. In fact this statement is still present in ARM DDI 0487A.i. 59 * 60 * Unfortunately "is a 32-bit register" has a very special meaning for 61 * system registers. It means that "the upper bits, bits[63:32], are 62 * RES0.". RES0 is heavily used in the ARM architecture documents as a 63 * way to leave space for future architecture changes. So to translate a 64 * little for people who don't spend their spare time reading ARM architecture 65 * manuals, what "is a 32-bit register" actually means in this context is 66 * "is a 64-bit register but one with no meaning allocated to any of the 67 * upper 32-bits... *yet*". 68 * 69 * Perhaps then we should not be surprised that this has led to some 70 * confusion. Specifically a patch, influenced by the above translation, 71 * that extended PSTATE to 64-bit was accepted into gdb-7.7 but the patch 72 * was reverted in gdb-7.8.1 and all later releases, when this was 73 * discovered to be an undocumented protocol change. 74 * 75 * So... it is *not* wrong for us to only allocate 32-bits to PSTATE 76 * here even though the kernel itself allocates 64-bits for the same 77 * state. That is because this bit of code tells the kernel how the gdb 78 * remote protocol (well most versions of it) describes the register state. 79 * 80 * Note that if you are using one of the versions of gdb that supports 81 * the gdb-7.7 version of the protocol you cannot use kgdb directly 82 * without providing a custom register description (gdb can load new 83 * protocol descriptions at runtime). 84 */ 85 86#define _GP_REGS 33 87#define _FP_REGS 32 88#define _EXTRA_REGS 3 89/* 90 * general purpose registers size in bytes. 91 * pstate is only 4 bytes. subtract 4 bytes 92 */ 93#define GP_REG_BYTES (_GP_REGS * 8) 94#define DBG_MAX_REG_NUM (_GP_REGS + _FP_REGS + _EXTRA_REGS) 95 96/* 97 * Size of I/O buffer for gdb packet. 98 * considering to hold all register contents, size is set 99 */ 100 101#define BUFMAX 2048 102 103/* 104 * Number of bytes required for gdb_regs buffer. 105 * _GP_REGS: 8 bytes, _FP_REGS: 16 bytes and _EXTRA_REGS: 4 bytes each 106 * GDB fails to connect for size beyond this with error 107 * "'g' packet reply is too long" 108 */ 109 110#define NUMREGBYTES ((_GP_REGS * 8) + (_FP_REGS * 16) + \ 111 (_EXTRA_REGS * 4)) 112 113#endif /* __ASM_KGDB_H */ 114