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 int kgdb_brk_handler(struct pt_regs *regs, unsigned long esr); 28 int kgdb_compiled_brk_handler(struct pt_regs *regs, unsigned long esr); 29 #ifdef CONFIG_KGDB 30 int kgdb_single_step_handler(struct pt_regs *regs, unsigned long esr); 31 #else 32 static inline int kgdb_single_step_handler(struct pt_regs *regs, 33 unsigned long esr) 34 { 35 return DBG_HOOK_ERROR; 36 } 37 #endif 38 39 #endif /* !__ASSEMBLY__ */ 40 41 /* 42 * gdb remote procotol (well most versions of it) expects the following 43 * register layout. 44 * 45 * General purpose regs: 46 * r0-r30: 64 bit 47 * sp,pc : 64 bit 48 * pstate : 32 bit 49 * Total: 33 + 1 50 * FPU regs: 51 * f0-f31: 128 bit 52 * fpsr & fpcr: 32 bit 53 * Total: 32 + 2 54 * 55 * To expand a little on the "most versions of it"... when the gdb remote 56 * protocol for AArch64 was developed it depended on a statement in the 57 * Architecture Reference Manual that claimed "SPSR_ELx is a 32-bit register". 58 * and, as a result, allocated only 32-bits for the PSTATE in the remote 59 * protocol. In fact this statement is still present in ARM DDI 0487A.i. 60 * 61 * Unfortunately "is a 32-bit register" has a very special meaning for 62 * system registers. It means that "the upper bits, bits[63:32], are 63 * RES0.". RES0 is heavily used in the ARM architecture documents as a 64 * way to leave space for future architecture changes. So to translate a 65 * little for people who don't spend their spare time reading ARM architecture 66 * manuals, what "is a 32-bit register" actually means in this context is 67 * "is a 64-bit register but one with no meaning allocated to any of the 68 * upper 32-bits... *yet*". 69 * 70 * Perhaps then we should not be surprised that this has led to some 71 * confusion. Specifically a patch, influenced by the above translation, 72 * that extended PSTATE to 64-bit was accepted into gdb-7.7 but the patch 73 * was reverted in gdb-7.8.1 and all later releases, when this was 74 * discovered to be an undocumented protocol change. 75 * 76 * So... it is *not* wrong for us to only allocate 32-bits to PSTATE 77 * here even though the kernel itself allocates 64-bits for the same 78 * state. That is because this bit of code tells the kernel how the gdb 79 * remote protocol (well most versions of it) describes the register state. 80 * 81 * Note that if you are using one of the versions of gdb that supports 82 * the gdb-7.7 version of the protocol you cannot use kgdb directly 83 * without providing a custom register description (gdb can load new 84 * protocol descriptions at runtime). 85 */ 86 87 #define _GP_REGS 33 88 #define _FP_REGS 32 89 #define _EXTRA_REGS 3 90 /* 91 * general purpose registers size in bytes. 92 * pstate is only 4 bytes. subtract 4 bytes 93 */ 94 #define GP_REG_BYTES (_GP_REGS * 8) 95 #define DBG_MAX_REG_NUM (_GP_REGS + _FP_REGS + _EXTRA_REGS) 96 97 /* 98 * Size of I/O buffer for gdb packet. 99 * considering to hold all register contents, size is set 100 */ 101 102 #define BUFMAX 2048 103 104 /* 105 * Number of bytes required for gdb_regs buffer. 106 * _GP_REGS: 8 bytes, _FP_REGS: 16 bytes and _EXTRA_REGS: 4 bytes each 107 * GDB fails to connect for size beyond this with error 108 * "'g' packet reply is too long" 109 */ 110 111 #define NUMREGBYTES ((_GP_REGS * 8) + (_FP_REGS * 16) + \ 112 (_EXTRA_REGS * 4)) 113 114 #endif /* __ASM_KGDB_H */ 115