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403b48aad5
Software stepping checks for the correct handler by iterating over a list of dynamically registered handlers and calling all of them until one handles the exception. This is the only generic way to handle software stepping handlers in arm64 as the exception does not provide an immediate that could be checked, contrary to software breakpoints. However, the registration mechanism is not exported and has only two current users : the KGDB stepping handler, and the uprobe single step handler. Given that one comes from user mode and the other from kernel mode, call the appropriate one by checking the source EL of the exception. Add a stand-in that returns DBG_HOOK_ERROR when the configuration options are not enabled. Remove `arch_init_uprobes()` as it is not useful anymore and is specific to arm64. Unify the naming of the handler to XXX_single_step_handler(), making it clear they are related. Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com> Tested-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Reviewed-by: Will Deacon <will@kernel.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20250707114109.35672-5-ada.coupriediaz@arm.com Signed-off-by: Will Deacon <will@kernel.org>
114 lines
3.6 KiB
C
114 lines
3.6 KiB
C
/* 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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int kgdb_brk_handler(struct pt_regs *regs, unsigned long esr);
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int kgdb_compiled_brk_handler(struct pt_regs *regs, unsigned long esr);
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#ifdef CONFIG_KGDB
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int kgdb_single_step_handler(struct pt_regs *regs, unsigned long esr);
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#else
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static inline int kgdb_single_step_handler(struct pt_regs *regs,
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unsigned long esr)
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{
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return DBG_HOOK_ERROR;
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}
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#endif
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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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