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riscv: kprobes: implement the branch instructions

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This has been tested by probing a module that contains each of the
flavors of branches we have.

Signed-off-by: Chen Lifu <chenlifu@huawei.com>
[Palmer: commit message, fix kconfig errors]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
This commit is contained in:
Chen Lifu 2021-06-29 10:34:55 +08:00 committed by Palmer Dabbelt
parent b7d2be48cc
commit 67979e927d
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GPG Key ID: 2E1319F35FBB1889
2 changed files with 79 additions and 2 deletions
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3
arch/riscv/kernel/probes/decode-insn.c
View File

@ -38,11 +38,10 @@ riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
RISCV_INSN_REJECTED(c_ebreak, insn);
#endif
RISCV_INSN_REJECTED(branch, insn);
RISCV_INSN_SET_SIMULATE(jal, insn);
RISCV_INSN_SET_SIMULATE(jalr, insn);
RISCV_INSN_SET_SIMULATE(auipc, insn);
RISCV_INSN_SET_SIMULATE(branch, insn);
return INSN_GOOD;
}

78
arch/riscv/kernel/probes/simulate-insn.c
View File

@ -117,3 +117,81 @@ bool __kprobes simulate_auipc(u32 opcode, unsigned long addr, struct pt_regs *re
return true;
}
#define branch_rs1_idx(opcode) \
(((opcode) >> 15) & 0x1f)
#define branch_rs2_idx(opcode) \
(((opcode) >> 20) & 0x1f)
#define branch_funct3(opcode) \
(((opcode) >> 12) & 0x7)
#define branch_imm(opcode) \
(((((opcode) >> 8) & 0xf ) << 1) | \
((((opcode) >> 25) & 0x3f) << 5) | \
((((opcode) >> 7) & 0x1 ) << 11) | \
((((opcode) >> 31) & 0x1 ) << 12))
#define branch_offset(opcode) \
sign_extend32((branch_imm(opcode)), 12)
#define BRANCH_BEQ 0x0
#define BRANCH_BNE 0x1
#define BRANCH_BLT 0x4
#define BRANCH_BGE 0x5
#define BRANCH_BLTU 0x6
#define BRANCH_BGEU 0x7
bool __kprobes simulate_branch(u32 opcode, unsigned long addr, struct pt_regs *regs)
{
/*
* branch instructions:
* 31 30 25 24 20 19 15 14 12 11 8 7 6 0
* | imm[12] | imm[10:5] | rs2 | rs1 | funct3 | imm[4:1] | imm[11] | opcode |
* 1 6 5 5 3 4 1 7
* imm[12|10:5] rs2 rs1 000 imm[4:1|11] 1100011 BEQ
* imm[12|10:5] rs2 rs1 001 imm[4:1|11] 1100011 BNE
* imm[12|10:5] rs2 rs1 100 imm[4:1|11] 1100011 BLT
* imm[12|10:5] rs2 rs1 101 imm[4:1|11] 1100011 BGE
* imm[12|10:5] rs2 rs1 110 imm[4:1|11] 1100011 BLTU
* imm[12|10:5] rs2 rs1 111 imm[4:1|11] 1100011 BGEU
*/
s32 offset;
s32 offset_tmp;
unsigned long rs1_val;
unsigned long rs2_val;
if (!rv_insn_reg_get_val(regs, branch_rs1_idx(opcode), &rs1_val) ||
!rv_insn_reg_get_val(regs, branch_rs2_idx(opcode), &rs2_val))
return false;
offset_tmp = branch_offset(opcode);
switch (branch_funct3(opcode)) {
case BRANCH_BEQ:
offset = (rs1_val == rs2_val) ? offset_tmp : 4;
break;
case BRANCH_BNE:
offset = (rs1_val != rs2_val) ? offset_tmp : 4;
break;
case BRANCH_BLT:
offset = ((long)rs1_val < (long)rs2_val) ? offset_tmp : 4;
break;
case BRANCH_BGE:
offset = ((long)rs1_val >= (long)rs2_val) ? offset_tmp : 4;
break;
case BRANCH_BLTU:
offset = (rs1_val < rs2_val) ? offset_tmp : 4;
break;
case BRANCH_BGEU:
offset = (rs1_val >= rs2_val) ? offset_tmp : 4;
break;
default:
return false;
}
instruction_pointer_set(regs, addr + offset);
return true;
}