Pu Lehui <pulehui@xxxxxxxxxxxxxxx> writes: > From: Pu Lehui <pulehui@xxxxxxxxxx> > > This patch adds 12 function arguments support for riscv64 bpf > trampoline. The current bpf trampoline supports <= sizeof(u64) bytes > scalar arguments [0] and <= 16 bytes struct arguments [1]. Therefore, we > focus on the situation where scalars are at most XLEN bits and > aggregates whose total size does not exceed 2×XLEN bits in the riscv > calling convention [2]. > > Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6184 [0] > Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6769 [1] > Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/download/draft-20230929-e5c800e661a53efe3c2678d71a306323b60eb13b/riscv-abi.pdf [2] > Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx> > Acked-by: Björn Töpel <bjorn@xxxxxxxxxx> > Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx> > --- > arch/riscv/net/bpf_jit_comp64.c | 66 +++++++++++++++++++++++---------- > 1 file changed, 47 insertions(+), 19 deletions(-) > > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c > index 351e1484205e..685c7389ae7e 100644 > --- a/arch/riscv/net/bpf_jit_comp64.c > +++ b/arch/riscv/net/bpf_jit_comp64.c > @@ -15,6 +15,7 @@ > #include <asm/percpu.h> > #include "bpf_jit.h" > > +#define RV_MAX_REG_ARGS 8 > #define RV_FENTRY_NINSNS 2 > /* imm that allows emit_imm to emit max count insns */ > #define RV_MAX_COUNT_IMM 0x7FFF7FF7FF7FF7FF > @@ -692,26 +693,45 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type, > return ret; > } > > -static void store_args(int nregs, int args_off, struct rv_jit_context *ctx) > +static void store_args(int nr_arg_slots, int args_off, struct rv_jit_context *ctx) > { > int i; > > - for (i = 0; i < nregs; i++) { > - emit_sd(RV_REG_FP, -args_off, RV_REG_A0 + i, ctx); > + for (i = 0; i < nr_arg_slots; i++) { > + if (i < RV_MAX_REG_ARGS) { > + emit_sd(RV_REG_FP, -args_off, RV_REG_A0 + i, ctx); > + } else { > + /* skip slots for T0 and FP of traced function */ > + emit_ld(RV_REG_T1, 16 + (i - RV_MAX_REG_ARGS) * 8, RV_REG_FP, ctx); > + emit_sd(RV_REG_FP, -args_off, RV_REG_T1, ctx); > + } > args_off -= 8; > } > } > > -static void restore_args(int nregs, int args_off, struct rv_jit_context *ctx) > +static void restore_args(int nr_reg_args, int args_off, struct rv_jit_context *ctx) > { > int i; > > - for (i = 0; i < nregs; i++) { > + for (i = 0; i < nr_reg_args; i++) { > emit_ld(RV_REG_A0 + i, -args_off, RV_REG_FP, ctx); > args_off -= 8; > } > } > > +static void restore_stack_args(int nr_stack_args, int args_off, int stk_arg_off, > + struct rv_jit_context *ctx) > +{ > + int i; > + > + for (i = 0; i < nr_stack_args; i++) { > + emit_ld(RV_REG_T1, -(args_off - RV_MAX_REG_ARGS * 8), RV_REG_FP, ctx); > + emit_sd(RV_REG_FP, -stk_arg_off, RV_REG_T1, ctx); > + args_off -= 8; > + stk_arg_off -= 8; > + } > +} > + > static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_off, > int run_ctx_off, bool save_ret, struct rv_jit_context *ctx) > { > @@ -784,8 +804,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > { > int i, ret, offset; > int *branches_off = NULL; > - int stack_size = 0, nregs = m->nr_args; > - int retval_off, args_off, nregs_off, ip_off, run_ctx_off, sreg_off; > + int stack_size = 0, nr_arg_slots = 0; > + int retval_off, args_off, nregs_off, ip_off, run_ctx_off, sreg_off, stk_arg_off; > struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY]; > struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT]; > struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN]; > @@ -831,20 +851,21 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > * FP - sreg_off [ callee saved reg ] > * > * [ pads ] pads for 16 bytes alignment > + * > + * [ stack_argN ] > + * [ ... ] > + * FP - stk_arg_off [ stack_arg1 ] BPF_TRAMP_F_CALL_ORIG > */ > > if (flags & (BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_SHARE_IPMODIFY)) > return -ENOTSUPP; > > - /* extra regiters for struct arguments */ > - for (i = 0; i < m->nr_args; i++) > - if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) > - nregs += round_up(m->arg_size[i], 8) / 8 - 1; > - > - /* 8 arguments passed by registers */ > - if (nregs > 8) > + if (m->nr_args > MAX_BPF_FUNC_ARGS) > return -ENOTSUPP; > > + for (i = 0; i < m->nr_args; i++) > + nr_arg_slots += round_up(m->arg_size[i], 8) / 8; > + > /* room of trampoline frame to store return address and frame pointer */ > stack_size += 16; > > @@ -854,7 +875,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > retval_off = stack_size; > } > > - stack_size += nregs * 8; > + stack_size += nr_arg_slots * 8; > args_off = stack_size; > > stack_size += 8; > @@ -871,8 +892,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, > stack_size += 8; > sreg_off = stack_size; > > + if (nr_arg_slots - RV_MAX_REG_ARGS > 0) > + stack_size += (nr_arg_slots - RV_MAX_REG_ARGS) * 8; Hi Pu, Although this is merged now, while working on this for arm64 I realised that the above doesn't check for BPF_TRAMP_F_CALL_ORIG and can waste some stack space, we should change this to: if ((flags & BPF_TRAMP_F_CALL_ORIG) && (nr_arg_slots - RV_MAX_REG_ARGS > 0)) stack_size += (nr_arg_slots - RV_MAX_REG_ARGS) * 8; It will save some stack space when BPF_TRAMP_F_CALL_ORIG is not set? I can send a patch if you think this is worth fixing. Thanks, Puranjay
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