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Subject[PATCH 1/3] riscv: kprobes: simulate c.j instruction
Date
kprobes currently rejects c.j instruction. Implement it.

Signed-off-by: Nam Cao <namcaov@gmail.com>
---
arch/riscv/kernel/probes/decode-insn.c | 3 ++-
arch/riscv/kernel/probes/simulate-insn.c | 24 ++++++++++++++++++++++++
arch/riscv/kernel/probes/simulate-insn.h | 1 +
3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c
index 64f6183b4717..39adb07a342d 100644
--- a/arch/riscv/kernel/probes/decode-insn.c
+++ b/arch/riscv/kernel/probes/decode-insn.c
@@ -29,13 +29,14 @@ riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
* TODO: the REJECTED ones below need to be implemented
*/
#ifdef CONFIG_RISCV_ISA_C
- RISCV_INSN_REJECTED(c_j, insn);
RISCV_INSN_REJECTED(c_jr, insn);
RISCV_INSN_REJECTED(c_jal, insn);
RISCV_INSN_REJECTED(c_jalr, insn);
RISCV_INSN_REJECTED(c_beqz, insn);
RISCV_INSN_REJECTED(c_bnez, insn);
RISCV_INSN_REJECTED(c_ebreak, insn);
+
+ RISCV_INSN_SET_SIMULATE(c_j, insn);
#endif

RISCV_INSN_SET_SIMULATE(jal, insn);
diff --git a/arch/riscv/kernel/probes/simulate-insn.c b/arch/riscv/kernel/probes/simulate-insn.c
index 7441ac8a6843..3ba45c612cd8 100644
--- a/arch/riscv/kernel/probes/simulate-insn.c
+++ b/arch/riscv/kernel/probes/simulate-insn.c
@@ -188,3 +188,27 @@ bool __kprobes simulate_branch(u32 opcode, unsigned long addr, struct pt_regs *r

return true;
}
+
+bool __kprobes simulate_c_j(u32 opcode, unsigned long addr, struct pt_regs *regs)
+{
+ /*
+ * 15 13 12 2 1 0
+ * | funct3 | offset[11|4|9:8|10|6|7|3:1|5] | opcode |
+ * 3 11 2
+ */
+
+ s32 offset;
+
+ offset = ((opcode >> 3) & 0x7) << 1;
+ offset |= ((opcode >> 11) & 0x1) << 4;
+ offset |= ((opcode >> 2) & 0x1) << 5;
+ offset |= ((opcode >> 7) & 0x1) << 6;
+ offset |= ((opcode >> 6) & 0x1) << 7;
+ offset |= ((opcode >> 9) & 0x3) << 8;
+ offset |= ((opcode >> 8) & 0x1) << 10;
+ offset |= ((opcode >> 12) & 0x1) << 11;
+
+ instruction_pointer_set(regs, addr + sign_extend32(offset, 11));
+
+ return true;
+}
diff --git a/arch/riscv/kernel/probes/simulate-insn.h b/arch/riscv/kernel/probes/simulate-insn.h
index 61e35db31001..4bd6c266e7d3 100644
--- a/arch/riscv/kernel/probes/simulate-insn.h
+++ b/arch/riscv/kernel/probes/simulate-insn.h
@@ -24,5 +24,6 @@ bool simulate_auipc(u32 opcode, unsigned long addr, struct pt_regs *regs);
bool simulate_branch(u32 opcode, unsigned long addr, struct pt_regs *regs);
bool simulate_jal(u32 opcode, unsigned long addr, struct pt_regs *regs);
bool simulate_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs);
+bool simulate_c_j(u32 opcode, unsigned long addr, struct pt_regs *regs);

#endif /* _RISCV_KERNEL_PROBES_SIMULATE_INSN_H */
--
2.34.1
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