9f564b92cf
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>
51 lines
1 KiB
C
51 lines
1 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef _ASM_RISCV_UPROBES_H
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#define _ASM_RISCV_UPROBES_H
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#include <asm/probes.h>
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#include <asm/patch.h>
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#include <asm/bug.h>
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#define MAX_UINSN_BYTES 8
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#ifdef CONFIG_RISCV_ISA_C
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#define UPROBE_SWBP_INSN __BUG_INSN_16
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#define UPROBE_SWBP_INSN_SIZE 2
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#else
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#define UPROBE_SWBP_INSN __BUG_INSN_32
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#define UPROBE_SWBP_INSN_SIZE 4
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#endif
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#define UPROBE_XOL_SLOT_BYTES MAX_UINSN_BYTES
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typedef u32 uprobe_opcode_t;
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struct arch_uprobe_task {
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unsigned long saved_cause;
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};
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struct arch_uprobe {
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union {
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u8 insn[MAX_UINSN_BYTES];
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u8 ixol[MAX_UINSN_BYTES];
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};
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struct arch_probe_insn api;
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unsigned long insn_size;
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bool simulate;
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};
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#ifdef CONFIG_UPROBES
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bool uprobe_breakpoint_handler(struct pt_regs *regs);
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bool uprobe_single_step_handler(struct pt_regs *regs);
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#else
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static inline bool uprobe_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 uprobe_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_UPROBES */
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#endif /* _ASM_RISCV_UPROBES_H */
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