| Message ID | 20210629023455.280998-1-chenlifu@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next,1/2] riscv: implemented auipc simulate instruction | expand |
On Mon, 28 Jun 2021 19:34:54 PDT (-0700), chenlifu@huawei.com wrote: > To test the kprobe-based event tracing, we prepare > a kernel module 'kprobe_test.ko' to add the probes. > The assembly codes (partially) of the module are as follows: > ... > 0000000000000000 <kprobe_test_branch>: > ... > 0000000000000038 <.LVL1>: > 38: 00000597 auipc a1,0x0 > 3c: 00058593 mv a1,a1 > ... > > Test the kprobe-based event tracing in qemu-system-riscv64: > First, install the kprobe test module: > insmod /root/kprobe_test.ko > > Then, add a probe as a new event at an 'auipc' instruction, > the following error occurs due to the instruction not allowed to probe yet: > echo "p:auipc kprobe_test:kprobe_test_branch+0x38 epc=%epc opcode=+0(%epc):x32" >> /sys/kernel/debug/tracing/kprobe_events > sh: write error: Invalid argument > > This patch implemented the 'auipc' simulate instruction and allowed to probe it. > Merge this patch and perform the test again, the test results are as follows: > First, add a probe at the 'auipc' instruction: > echo "p:auipc kprobe_test:kprobe_test_branch+0x38 epc=%epc opcode=+0(%epc):x32" >> /sys/kernel/debug/tracing/kprobe_events > echo 1 > /sys/kernel/debug/tracing/events/kprobes/auipc/enable > > Then, do something to run to the probe. > After that, see the traced information: > cat /sys/kernel/debug/tracing/trace > sysctl-58 [001] d... 179.126350: auipc: (kprobe_test_branch+0x38/0x10e [kprobe_test]) epc=0xffffffff016122aa opcode=0x100073 > > Now we can see the traced information. > The actual address of the symbol 'kprobe_test_branch' is as follows: > cat /proc/kallsyms | grep kprobe_test_branch > ffffffff01612272 t kprobe_test_branch [kprobe_test] > > Based on the traced information and the actual address of the symbol > 'kprobe_test_branch', we can also see that the 'auipc' instruction > has been replaced by 'ebreak(0x100073)' instruction. > > -------- > > Signed-off-by: Chen Lifu <chenlifu@huawei.com> > --- > arch/riscv/kernel/probes/decode-insn.c | 2 +- > arch/riscv/kernel/probes/simulate-insn.c | 34 ++++++++++++++++++++++++ > 2 files changed, 35 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c > index 0ed043acc882..5eb03fb61450 100644 > --- 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 2519ce26377d..b81719522d5c 100644 > --- 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; > +} Thanks. These are on for-next, with the checkpatch errors fixed and the commit messages mostly removed -- it was all pretty awkwardly phrased so I didn't want to clean it up.
diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c index 0ed043acc882..5eb03fb61450 100644 --- 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 2519ce26377d..b81719522d5c 100644 --- 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; +}
To test the kprobe-based event tracing, we prepare a kernel module 'kprobe_test.ko' to add the probes. The assembly codes (partially) of the module are as follows: ... 0000000000000000 <kprobe_test_branch>: ... 0000000000000038 <.LVL1>: 38: 00000597 auipc a1,0x0 3c: 00058593 mv a1,a1 ... Test the kprobe-based event tracing in qemu-system-riscv64: First, install the kprobe test module: insmod /root/kprobe_test.ko Then, add a probe as a new event at an 'auipc' instruction, the following error occurs due to the instruction not allowed to probe yet: echo "p:auipc kprobe_test:kprobe_test_branch+0x38 epc=%epc opcode=+0(%epc):x32" >> /sys/kernel/debug/tracing/kprobe_events sh: write error: Invalid argument This patch implemented the 'auipc' simulate instruction and allowed to probe it. Merge this patch and perform the test again, the test results are as follows: First, add a probe at the 'auipc' instruction: echo "p:auipc kprobe_test:kprobe_test_branch+0x38 epc=%epc opcode=+0(%epc):x32" >> /sys/kernel/debug/tracing/kprobe_events echo 1 > /sys/kernel/debug/tracing/events/kprobes/auipc/enable Then, do something to run to the probe. After that, see the traced information: cat /sys/kernel/debug/tracing/trace sysctl-58 [001] d... 179.126350: auipc: (kprobe_test_branch+0x38/0x10e [kprobe_test]) epc=0xffffffff016122aa opcode=0x100073 Now we can see the traced information. The actual address of the symbol 'kprobe_test_branch' is as follows: cat /proc/kallsyms | grep kprobe_test_branch ffffffff01612272 t kprobe_test_branch [kprobe_test] Based on the traced information and the actual address of the symbol 'kprobe_test_branch', we can also see that the 'auipc' instruction has been replaced by 'ebreak(0x100073)' instruction. -------- Signed-off-by: Chen Lifu <chenlifu@huawei.com> --- arch/riscv/kernel/probes/decode-insn.c | 2 +- arch/riscv/kernel/probes/simulate-insn.c | 34 ++++++++++++++++++++++++ 2 files changed, 35 insertions(+), 1 deletion(-)