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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* AArch64 KGDB support
*
* Based on arch/arm/include/kgdb.h
*
* Copyright (C) 2013 Cavium Inc.
* Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
*/
#ifndef __ARM_KGDB_H
#define __ARM_KGDB_H
#include <linux/ptrace.h>
#include <asm/debug-monitors.h>
#ifndef __ASSEMBLY__
static inline void arch_kgdb_breakpoint(void)
{
asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM));
}
extern void kgdb_handle_bus_error(void);
extern int kgdb_fault_expected;
#endif /* !__ASSEMBLY__ */
/*
* gdb remote procotol (well most versions of it) expects the following
* register layout.
*
* General purpose regs:
* r0-r30: 64 bit
* sp,pc : 64 bit
* pstate : 32 bit
* Total: 33 + 1
* FPU regs:
* f0-f31: 128 bit
* fpsr & fpcr: 32 bit
* Total: 32 + 2
*
* To expand a little on the "most versions of it"... when the gdb remote
* protocol for AArch64 was developed it depended on a statement in the
* Architecture Reference Manual that claimed "SPSR_ELx is a 32-bit register".
* and, as a result, allocated only 32-bits for the PSTATE in the remote
* protocol. In fact this statement is still present in ARM DDI 0487A.i.
*
* Unfortunately "is a 32-bit register" has a very special meaning for
* system registers. It means that "the upper bits, bits[63:32], are
* RES0.". RES0 is heavily used in the ARM architecture documents as a
* way to leave space for future architecture changes. So to translate a
* little for people who don't spend their spare time reading ARM architecture
* manuals, what "is a 32-bit register" actually means in this context is
* "is a 64-bit register but one with no meaning allocated to any of the
* upper 32-bits... *yet*".
*
* Perhaps then we should not be surprised that this has led to some
* confusion. Specifically a patch, influenced by the above translation,
* that extended PSTATE to 64-bit was accepted into gdb-7.7 but the patch
* was reverted in gdb-7.8.1 and all later releases, when this was
* discovered to be an undocumented protocol change.
*
* So... it is *not* wrong for us to only allocate 32-bits to PSTATE
* here even though the kernel itself allocates 64-bits for the same
* state. That is because this bit of code tells the kernel how the gdb
* remote protocol (well most versions of it) describes the register state.
*
* Note that if you are using one of the versions of gdb that supports
* the gdb-7.7 version of the protocol you cannot use kgdb directly
* without providing a custom register description (gdb can load new
* protocol descriptions at runtime).
*/
#define _GP_REGS 33
#define _FP_REGS 32
#define _EXTRA_REGS 3
/*
* general purpose registers size in bytes.
* pstate is only 4 bytes. subtract 4 bytes
*/
#define GP_REG_BYTES (_GP_REGS * 8)
#define DBG_MAX_REG_NUM (_GP_REGS + _FP_REGS + _EXTRA_REGS)
/*
* Size of I/O buffer for gdb packet.
* considering to hold all register contents, size is set
*/
#define BUFMAX 2048
/*
* Number of bytes required for gdb_regs buffer.
* _GP_REGS: 8 bytes, _FP_REGS: 16 bytes and _EXTRA_REGS: 4 bytes each
* GDB fails to connect for size beyond this with error
* "'g' packet reply is too long"
*/
#define NUMREGBYTES ((_GP_REGS * 8) + (_FP_REGS * 16) + \
(_EXTRA_REGS * 4))
#endif /* __ASM_KGDB_H */
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