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

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

Signed-off-by: Nam Cao <namcaov@gmail.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/db8b7787e9208654cca50484f68334f412be2ea9.1690704360.git.namcaov@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Nam Cao 2023-07-30 10:27:08 +02:00 committed by Palmer Dabbelt
parent a93892974f
commit b18256d9b7
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
3 changed files with 41 additions and 2 deletions
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4
arch/riscv/kernel/probes/decode-insn.c
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@ -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);

37
arch/riscv/kernel/probes/simulate-insn.c
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@ -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);
}

2
arch/riscv/kernel/probes/simulate-insn.h
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@ -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 */