Unverified Commit b18256d9 authored by Nam Cao's avatar Nam Cao Committed by Palmer Dabbelt
Browse files

riscv: kprobes: simulate c.jr and c.jalr instructions 



kprobes currently rejects c.jr and c.jalr instructions. Implement them.

Signed-off-by: default avatarNam Cao <namcaov@gmail.com>
Reviewed-by: default avatarCharlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/db8b7787e9208654cca50484f68334f412be2ea9.1690704360.git.namcaov@gmail.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent a9389297

arch/riscv/kernel/probes/decode-insn.c

+2 −2
Original line number Diff line number Diff line
@@ -29,14 +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_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);

	RISCV_INSN_SET_SIMULATE(c_jr,		insn);

	RISCV_INSN_SET_SIMULATE(c_jalr,		insn);

#endif



	RISCV_INSN_SET_SIMULATE(jal,		insn);

arch/riscv/kernel/probes/simulate-insn.c

+37 −0
Original line number Diff line number Diff line
@@ -212,3 +212,40 @@ bool __kprobes simulate_c_j(u32 opcode, unsigned long addr, struct pt_regs *regs 


	return true;

}



static bool __kprobes simulate_c_jr_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs,

					 bool is_jalr)

{

	/*

	 *  15    12 11  7 6   2 1  0

	 * | funct4 | rs1 | rs2 | op |

	 *     4       5     5    2

	 */



	unsigned long jump_addr;



	u32 rs1 = (opcode >> 7) & 0x1f;



	if (rs1 == 0) /* C.JR is only valid when rs1 != x0 */

		return false;



	if (!rv_insn_reg_get_val(regs, rs1, &jump_addr))

		return false;



	if (is_jalr && !rv_insn_reg_set_val(regs, 1, addr + 2))

		return false;



	instruction_pointer_set(regs, jump_addr);



	return true;

}



bool __kprobes simulate_c_jr(u32 opcode, unsigned long addr, struct pt_regs *regs)

{

	return simulate_c_jr_jalr(opcode, addr, regs, false);

}



bool __kprobes simulate_c_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs)

{

	return simulate_c_jr_jalr(opcode, addr, regs, true);

}

arch/riscv/kernel/probes/simulate-insn.h

+2 −0
Original line number Diff line number Diff line
@@ -25,5 +25,7 @@ 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);

bool simulate_c_jr(u32 opcode, unsigned long addr, struct pt_regs *regs);

bool simulate_c_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs);



#endif /* _RISCV_KERNEL_PROBES_SIMULATE_INSN_H */