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 */ 103