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