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RISC-V software breakpoint trap handlers are used for {k,u}probes.
When trapping from kernelmode, only the kernelmode handlers should be
considered. Vice versa, only usermode handlers for usermode
traps. This is not the case on RISC-V, which can trigger a bug if a
userspace process uses uprobes, and a WARN() is triggered from
kernelmode (which is implemented via {c.,}ebreak).
The kernel will trap on the kernelmode {c.,}ebreak, look for uprobes
handlers, realize incorrectly that uprobes need to be handled, and
exit the trap handler early. The trap returns to re-executing the
{c.,}ebreak, and enter an infinite trap-loop.
The issue was found running the BPF selftest [1].
Fix this issue by only considering the swbp/ss handlers for
kernel/usermode respectively. Also, move CONFIG ifdeffery from traps.c
to the asm/{k,u}probes.h headers.
Note that linux/uprobes.h only include asm/uprobes.h if CONFIG_UPROBES
is defined, which is why asm/uprobes.h needs to be unconditionally
included in traps.c
Link: https://lore.kernel.org/linux-riscv/87v8d19aun.fsf@all.your.base.are.belong.to.us/ # [1]
Fixes: 74784081aa ("riscv: Add uprobes supported")
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Nam Cao <namcaov@gmail.com>
Tested-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20230912065619.62020-1-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copied from arch/arm64/include/asm/kprobes.h
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*
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* Copyright (C) 2013 Linaro Limited
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* Copyright (C) 2017 SiFive
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*/
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#ifndef _ASM_RISCV_KPROBES_H
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#define _ASM_RISCV_KPROBES_H
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#include <asm-generic/kprobes.h>
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#ifdef CONFIG_KPROBES
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/percpu.h>
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#define __ARCH_WANT_KPROBES_INSN_SLOT
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#define MAX_INSN_SIZE 2
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#define flush_insn_slot(p) do { } while (0)
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#define kretprobe_blacklist_size 0
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#include <asm/probes.h>
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struct prev_kprobe {
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struct kprobe *kp;
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unsigned int status;
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};
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/* per-cpu kprobe control block */
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struct kprobe_ctlblk {
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unsigned int kprobe_status;
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unsigned long saved_status;
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struct prev_kprobe prev_kprobe;
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};
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void arch_remove_kprobe(struct kprobe *p);
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int kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr);
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bool kprobe_breakpoint_handler(struct pt_regs *regs);
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bool kprobe_single_step_handler(struct pt_regs *regs);
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#else
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static inline bool kprobe_breakpoint_handler(struct pt_regs *regs)
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{
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return false;
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}
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static inline bool kprobe_single_step_handler(struct pt_regs *regs)
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{
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return false;
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}
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#endif /* CONFIG_KPROBES */
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#endif /* _ASM_RISCV_KPROBES_H */
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