From: Hengqi Chen Date: Thu, 23 Apr 2026 04:49:36 +0000 (+0800) Subject: LoongArch: BPF: Add fsession support for trampolines X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e815df29b6a5e59293500085a010d5882374cb3e;p=thirdparty%2Flinux.git LoongArch: BPF: Add fsession support for trampolines Implement BPF_TRACE_FSESSION support in LoongArch BPF JIT. The logic here is almost identical to what has been done in RISC-V JIT. The key changes are: - Allocate stack space for function meta and session cookies - Introduce invoke_bpf() as a wrapper around invoke_bpf_prog() that populates session cookies before each invocation - Implement bpf_jit_supports_fsession() callback Tested-by: Vincent Li Reviewed-by: Menglong Dong Signed-off-by: Hengqi Chen Signed-off-by: Huacai Chen --- diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index a6c001583083..ec3c25b45882 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -1737,6 +1737,29 @@ static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l, return ret; } +static int invoke_bpf(struct jit_ctx *ctx, struct bpf_tramp_links *tl, + int args_off, int retval_off, int run_ctx_off, + int func_meta_off, bool save_ret, u64 func_meta, int cookie_off) +{ + int i, cur_cookie = (cookie_off - args_off) / 8; + + for (i = 0; i < tl->nr_links; i++) { + int err; + + if (bpf_prog_calls_session_cookie(tl->links[i])) { + u64 meta = func_meta | ((u64)cur_cookie << BPF_TRAMP_COOKIE_INDEX_SHIFT); + + emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, meta); + cur_cookie--; + } + err = invoke_bpf_prog(ctx, tl->links[i], args_off, retval_off, run_ctx_off, save_ret); + if (err) + return err; + } + + return 0; +} + void *arch_alloc_bpf_trampoline(unsigned int size) { return bpf_prog_pack_alloc(size, jit_fill_hole); @@ -1788,8 +1811,10 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i void *func_addr, u32 flags) { int i, ret, save_ret; + int cookie_cnt, cookie_off; int stack_size, args_off, stk_args_off, nr_arg_slots = 0; - int retval_off, nregs_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off; + int retval_off, func_meta_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off; + unsigned long long func_meta; bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT; void *orig_call = func_addr; struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY]; @@ -1813,10 +1838,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i * [ ... ] * FP - args_off [ arg reg1 ] * - * FP - nregs_off [ arg regs count ] + * FP - func_meta_off [ regs count, etc ] * * FP - ip_off [ traced func ] BPF_TRAMP_F_IP_ARG * + * [ stack cookie N ] + * [ ... ] + * FP - cookie_off [ stack cookie 1 ] + * * FP - run_ctx_off [ bpf_tramp_run_ctx ] * * FP - sreg_off [ callee saved reg ] @@ -1859,9 +1888,9 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i stack_size += nr_arg_slots * 8; args_off = stack_size; - /* Room of trampoline frame to store args number */ + /* Room of function metadata, such as regs count */ stack_size += 8; - nregs_off = stack_size; + func_meta_off = stack_size; /* Room of trampoline frame to store ip address */ if (flags & BPF_TRAMP_F_IP_ARG) { @@ -1869,6 +1898,12 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i ip_off = stack_size; } + cookie_cnt = bpf_fsession_cookie_cnt(tlinks); + + /* Room for session cookies */ + stack_size += cookie_cnt * 8; + cookie_off = stack_size; + /* Room of trampoline frame to store struct bpf_tramp_run_ctx */ stack_size += round_up(sizeof(struct bpf_tramp_run_ctx), 8); run_ctx_off = stack_size; @@ -1929,10 +1964,20 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -ip_off, (u64)func_addr); /* store arg regs count */ - emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -nregs_off, nr_arg_slots); + func_meta = nr_arg_slots; + emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, func_meta); store_args(ctx, nr_arg_slots, args_off); + if (bpf_fsession_cnt(tlinks)) { + /* clear all session cookies' value */ + for (i = 0; i < cookie_cnt; i++) + emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -cookie_off + 8 * i); + + /* clear return value to make sure fentry always get 0 */ + emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -retval_off); + } + /* To traced function */ /* Ftrace jump skips 2 NOP instructions */ if (is_kernel_text((unsigned long)orig_call) || @@ -1949,9 +1994,9 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i return ret; } - for (i = 0; i < fentry->nr_links; i++) { - ret = invoke_bpf_prog(ctx, fentry->links[i], args_off, retval_off, - run_ctx_off, flags & BPF_TRAMP_F_RET_FENTRY_RET); + if (fentry->nr_links) { + ret = invoke_bpf(ctx, fentry, args_off, retval_off, run_ctx_off, func_meta_off, + flags & BPF_TRAMP_F_RET_FENTRY_RET, func_meta, cookie_off); if (ret) return ret; } @@ -1995,8 +2040,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i *branches[i] = larch_insn_gen_bne(LOONGARCH_GPR_T1, LOONGARCH_GPR_ZERO, offset); } - for (i = 0; i < fexit->nr_links; i++) { - ret = invoke_bpf_prog(ctx, fexit->links[i], args_off, retval_off, run_ctx_off, false); + /* Set "is_return" flag for fsession */ + func_meta |= (1ULL << BPF_TRAMP_IS_RETURN_SHIFT); + if (bpf_fsession_cnt(tlinks)) + emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, func_meta); + + if (fexit->nr_links) { + ret = invoke_bpf(ctx, fexit, args_off, retval_off, run_ctx_off, + func_meta_off, false, func_meta, cookie_off); if (ret) goto out; } @@ -2331,6 +2382,11 @@ bool bpf_jit_supports_arena(void) return true; } +bool bpf_jit_supports_fsession(void) +{ + return true; +} + /* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */ bool bpf_jit_supports_subprog_tailcalls(void) {