On Mon, Dec 05, 2022 at 04:31:08PM +0100, Heiko Stübner wrote: > Am Sonntag, 4. Dezember 2022, 18:46:20 CET schrieb Jisheng Zhang: > > Alternatives live in a different section, so offsets used by jal > > instruction will point to wrong locations after the patch got applied. > > > > Similar to arm64, adjust the location to consider that offset. > > > > Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxx> > > --- > > arch/riscv/include/asm/alternative.h | 2 ++ > > arch/riscv/kernel/alternative.c | 38 ++++++++++++++++++++++++++++ > > arch/riscv/kernel/cpufeature.c | 3 +++ > > 3 files changed, 43 insertions(+) > > > > diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h > > index c58ec3cc4bc3..33eae9541684 100644 > > --- a/arch/riscv/include/asm/alternative.h > > +++ b/arch/riscv/include/asm/alternative.h > > @@ -29,6 +29,8 @@ void apply_module_alternatives(void *start, size_t length); > > > > void riscv_alternative_fix_auipc_jalr(void *alt_ptr, unsigned int len, > > int patch_offset); > > +void riscv_alternative_fix_jal(void *alt_ptr, unsigned int len, > > + int patch_offset); > > > > struct alt_entry { > > void *old_ptr; /* address of original instruciton or data */ > > diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c > > index 292cc42dc3be..9d88375624b5 100644 > > --- a/arch/riscv/kernel/alternative.c > > +++ b/arch/riscv/kernel/alternative.c > > @@ -125,6 +125,44 @@ void riscv_alternative_fix_auipc_jalr(void *alt_ptr, unsigned int len, > > } > > } > > > > +#define to_jal_imm(value) \ > > + (((value & (RV_J_IMM_10_1_MASK << RV_J_IMM_10_1_OFF)) << RV_I_IMM_11_0_OPOFF) | \ > > + ((value & (RV_J_IMM_11_MASK << RV_J_IMM_11_OFF)) << RV_J_IMM_11_OPOFF) | \ > > + ((value & (RV_J_IMM_19_12_OPOFF << RV_J_IMM_19_12_OFF)) << RV_J_IMM_19_12_OPOFF) | \ > > + ((value & (1 << RV_J_IMM_SIGN_OFF)) << RV_J_IMM_SIGN_OPOFF)) > > + > > +void riscv_alternative_fix_jal(void *alt_ptr, unsigned int len, > > + int patch_offset) > > +{ > > I think we might want to unfiy this into a common function like > > riscv_alternative_fix_offsets(...) > > so that we only run through the code block once > > for (i = 0; i < num_instr; i++) { > if (riscv_insn_is_auipc_jalr(inst1, inst2)) { > riscv_alternative_fix_auipc_jalr(...) > continue; > } > > if (riscv_insn_is_jal(inst)) { > riscv_alternative_fix_jal(...) > continue; > } > } > > This would also remove the need from calling multiple functions > after patching alternatives. Yesterday, I also wanted to unify the two instruction fix into one. But that would need to roll back the riscv_alternative_fix_auipc_jalr() to your v1 version. And IMHO, it's better if you can split the Zbb string optimizations series into two: one for alternative improvements, another for Zbb. Then we may get the alternative improvements and this inst extension series merged in v6.2-rc1. > > Thoughts? > > > Heiko > > > + int num_instr = len / sizeof(u32); > > + unsigned int call; > > + int i; > > + int imm; > > + > > + for (i = 0; i < num_instr; i++) { > > + u32 inst = riscv_instruction_at(alt_ptr, i); > > + > > + if (!riscv_insn_is_jal(inst)) > > + continue; > > + > > + /* get and adjust new target address */ > > + imm = RV_EXTRACT_JTYPE_IMM(inst); > > + imm -= patch_offset; > > + > > + /* pick the original jal */ > > + call = inst; > > + > > + /* drop the old IMMs, all jal imm bits sit at 31:12 */ > > + call &= ~GENMASK(31, 12); > > + > > + /* add the adapted IMMs */ > > + call |= to_jal_imm(imm); > > + > > + /* patch the call place again */ > > + patch_text_nosync(alt_ptr + i * sizeof(u32), &call, 4); > > + } > > +} > > + > > /* > > * This is called very early in the boot process (directly after we run > > * a feature detect on the boot CPU). No need to worry about other CPUs > > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c > > index ba62a4ff5ccd..c743f0adc794 100644 > > --- a/arch/riscv/kernel/cpufeature.c > > +++ b/arch/riscv/kernel/cpufeature.c > > @@ -324,6 +324,9 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin, > > riscv_alternative_fix_auipc_jalr(alt->old_ptr, > > alt->alt_len, > > alt->old_ptr - alt->alt_ptr); > > + riscv_alternative_fix_jal(alt->old_ptr, > > + alt->alt_len, > > + alt->old_ptr - alt->alt_ptr); > > } > > } > > } > > > > > >