riscv: kprobes: implement the auipc instruction

This has been tested by probing a module that contains an auipc
instruction.

Signed-off-by: Chen Lifu <chenlifu@huawei.com>
[Palmer: commit message]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c
index 0ed043a..5eb03fb 100644 (file)
--- a/arch/riscv/kernel/probes/decode-insn.c
+++ b/arch/riscv/kernel/probes/decode-insn.c
@@ -38,11 +38,11 @@ riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
        RISCV_INSN_REJECTED(c_ebreak,           insn);
 #endif
 
-       RISCV_INSN_REJECTED(auipc,              insn);
        RISCV_INSN_REJECTED(branch,             insn);
 
        RISCV_INSN_SET_SIMULATE(jal,            insn);
        RISCV_INSN_SET_SIMULATE(jalr,           insn);
+       RISCV_INSN_SET_SIMULATE(auipc,          insn);
 
        return INSN_GOOD;
 }

diff --git a/arch/riscv/kernel/probes/simulate-insn.c b/arch/riscv/kernel/probes/simulate-insn.c
index 2519ce2..b817195 100644 (file)
--- a/arch/riscv/kernel/probes/simulate-insn.c
+++ b/arch/riscv/kernel/probes/simulate-insn.c
@@ -83,3 +83,37 @@ bool __kprobes simulate_jalr(u32 opcode, unsigned long addr, struct pt_regs *reg
 
        return ret;
 }
+
+#define auipc_rd_idx(opcode) \
+       ((opcode >> 7) & 0x1f)
+
+#define auipc_imm(opcode) \
+       ((((opcode) >> 12) & 0xfffff) << 12)
+
+#if __riscv_xlen == 64
+#define auipc_offset(opcode)   sign_extend64(auipc_imm(opcode), 31)
+#elif __riscv_xlen == 32
+#define auipc_offset(opcode)   auipc_imm(opcode)
+#else
+#error "Unexpected __riscv_xlen"
+#endif
+
+bool __kprobes simulate_auipc(u32 opcode, unsigned long addr, struct pt_regs *regs)
+{
+       /*
+        * auipc instruction:
+        *  31        12 11 7 6      0
+        * | imm[31:12] | rd | opcode |
+        *        20       5     7
+        */
+
+       u32 rd_idx = auipc_rd_idx(opcode);
+       unsigned long rd_val = addr + auipc_offset(opcode);
+
+       if (!rv_insn_reg_set_val(regs, rd_idx, rd_val))
+               return false;
+
+       instruction_pointer_set(regs, addr + 4);
+
+       return true;
+}