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riscv: kprobes: simulate c.beqz and c.bnez

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kprobes currently rejects instruction c.beqz and c.bnez. Implement them.

Signed-off-by: Nam Cao <namcaov@gmail.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/1d879dba4e4ee9a82e27625d6483b5c9cfed684f.1690704360.git.namcaov@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Nam Cao 2023-07-30 10:27:09 +02:00 committed by Palmer Dabbelt
parent b18256d9b7
commit d943705fba
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
3 changed files with 48 additions and 2 deletions
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4
arch/riscv/kernel/probes/decode-insn.c
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@ -30,13 +30,13 @@ riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
*/
#ifdef CONFIG_RISCV_ISA_C
RISCV_INSN_REJECTED(c_jal, 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);
RISCV_INSN_SET_SIMULATE(c_beqz, insn);
RISCV_INSN_SET_SIMULATE(c_bnez, insn);
#endif
RISCV_INSN_SET_SIMULATE(jal, insn);

44
arch/riscv/kernel/probes/simulate-insn.c
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@ -249,3 +249,47 @@ bool __kprobes simulate_c_jalr(u32 opcode, unsigned long addr, struct pt_regs *r
{
return simulate_c_jr_jalr(opcode, addr, regs, true);
}
static bool __kprobes simulate_c_bnez_beqz(u32 opcode, unsigned long addr, struct pt_regs *regs,
bool is_bnez)
{
/*
* 15 13 12 10 9 7 6 2 1 0
* | funct3 | offset[8|4:3] | rs1' | offset[7:6|2:1|5] | op |
* 3 3 3 5 2
*/
s32 offset;
u32 rs1;
unsigned long rs1_val;
rs1 = 0x8 | ((opcode >> 7) & 0x7);
if (!rv_insn_reg_get_val(regs, rs1, &rs1_val))
return false;
if ((rs1_val != 0 && is_bnez) || (rs1_val == 0 && !is_bnez)) {
offset = ((opcode >> 3) & 0x3) << 1;
offset |= ((opcode >> 10) & 0x3) << 3;
offset |= ((opcode >> 2) & 0x1) << 5;
offset |= ((opcode >> 5) & 0x3) << 6;
offset |= ((opcode >> 12) & 0x1) << 8;
offset = sign_extend32(offset, 8);
} else {
offset = 2;
}
instruction_pointer_set(regs, addr + offset);
return true;
}
bool __kprobes simulate_c_bnez(u32 opcode, unsigned long addr, struct pt_regs *regs)
{
return simulate_c_bnez_beqz(opcode, addr, regs, true);
}
bool __kprobes simulate_c_beqz(u32 opcode, unsigned long addr, struct pt_regs *regs)
{
return simulate_c_bnez_beqz(opcode, addr, regs, false);
}

2
arch/riscv/kernel/probes/simulate-insn.h
View File

@ -27,5 +27,7 @@ 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);
bool simulate_c_bnez(u32 opcode, unsigned long addr, struct pt_regs *regs);
bool simulate_c_beqz(u32 opcode, unsigned long addr, struct pt_regs *regs);
#endif /* _RISCV_KERNEL_PROBES_SIMULATE_INSN_H */