Commit 35b3515b authored by Menglong Dong's avatar Menglong Dong Committed by Alexei Starovoitov
Browse files

bpf, riscv: add fsession support for trampolines 



Implement BPF_TRACE_FSESSION support in the RISC-V trampoline JIT. The
logic here is similar to what we did in x86_64.

In order to simply the logic, we factor out the function invoke_bpf() for
fentry and fexit.

Signed-off-by: default avatarMenglong Dong <dongml2@chinatelecom.cn>
Tested-by: default avatarBjörn Töpel <bjorn@kernel.org>
Acked-by: default avatarBjörn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20260208053311.698352-3-dongml2@chinatelecom.cn


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Reviewed-by: default avatarPu Lehui <pulehui@huawei.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 93fd420d

arch/riscv/net/bpf_jit_comp64.c

+64 −10
Original line number Diff line number Diff line
@@ -996,6 +996,29 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of 
	return ret;

}



static int invoke_bpf(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, struct rv_jit_context *ctx)

{

	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(RV_REG_T1, -func_meta_off, meta, ctx);

			cur_cookie--;

		}

		err = invoke_bpf_prog(tl->links[i], args_off, retval_off, run_ctx_off,

				      save_ret, ctx);

		if (err)

			return err;

	}

	return 0;

}



static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,

					 const struct btf_func_model *m,

					 struct bpf_tramp_links *tlinks,
@@ -1005,13 +1028,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
	int i, ret, offset;

	int *branches_off = NULL;

	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;

	int retval_off, args_off, func_meta_off, ip_off, run_ctx_off, sreg_off, stk_arg_off;

	int cookie_off, cookie_cnt;

	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];

	bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT;

	void *orig_call = func_addr;

	bool save_ret;

	u64 func_meta;

	u32 insn;



	/* Two types of generated trampoline stack layout:
@@ -1042,10 +1067,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
	 *                  [ ...               ]

	 * FP - args_off    [ arg1              ]

	 *

	 * FP - nregs_off   [ 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	]
@@ -1077,14 +1106,20 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
	stack_size += nr_arg_slots * 8;

	args_off = stack_size;



	/* function metadata, such as regs count */

	stack_size += 8;

	nregs_off = stack_size;

	func_meta_off = stack_size;



	if (flags & BPF_TRAMP_F_IP_ARG) {

		stack_size += 8;

		ip_off = stack_size;

	}



	cookie_cnt = bpf_fsession_cookie_cnt(tlinks);

	/* room for session cookies */

	stack_size += cookie_cnt * 8;

	cookie_off = stack_size;



	stack_size += round_up(sizeof(struct bpf_tramp_run_ctx), 8);

	run_ctx_off = stack_size;
@@ -1132,10 +1167,19 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
	if (flags & BPF_TRAMP_F_IP_ARG)

		emit_store_stack_imm64(RV_REG_T1, -ip_off, (u64)func_addr, ctx);



	emit_store_stack_imm64(RV_REG_T1, -nregs_off, nr_arg_slots, ctx);

	func_meta = nr_arg_slots;

	emit_store_stack_imm64(RV_REG_T1, -func_meta_off, func_meta, ctx);



	store_args(nr_arg_slots, args_off, ctx);



	if (bpf_fsession_cnt(tlinks)) {

		/* clear all session cookies' value */

		for (i = 0; i < cookie_cnt; i++)

			emit_sd(RV_REG_FP, -cookie_off + 8 * i, RV_REG_ZERO, ctx);

		/* clear return value to make sure fentry always get 0 */

		emit_sd(RV_REG_FP, -retval_off, RV_REG_ZERO, ctx);

	}



	if (flags & BPF_TRAMP_F_CALL_ORIG) {

		emit_imm(RV_REG_A0, ctx->insns ? (const s64)im : RV_MAX_COUNT_IMM, ctx);

		ret = emit_call((const u64)__bpf_tramp_enter, true, ctx);
@@ -1143,9 +1187,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
			return ret;

	}



	for (i = 0; i < fentry->nr_links; i++) {

		ret = invoke_bpf_prog(fentry->links[i], args_off, retval_off, run_ctx_off,

				      flags & BPF_TRAMP_F_RET_FENTRY_RET, ctx);

	if (fentry->nr_links) {

		ret = invoke_bpf(fentry, args_off, retval_off, run_ctx_off, func_meta_off,

				 flags & BPF_TRAMP_F_RET_FENTRY_RET, func_meta, cookie_off, ctx);

		if (ret)

			return ret;

	}
@@ -1192,9 +1236,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 
		*(u32 *)(ctx->insns + branches_off[i]) = insn;

	}



	for (i = 0; i < fexit->nr_links; i++) {

		ret = invoke_bpf_prog(fexit->links[i], args_off, retval_off,

				      run_ctx_off, false, ctx);

	/* set "is_return" flag for fsession */

	func_meta |= (1ULL << BPF_TRAMP_IS_RETURN_SHIFT);

	if (bpf_fsession_cnt(tlinks))

		emit_store_stack_imm64(RV_REG_T1, -func_meta_off, func_meta, ctx);



	if (fexit->nr_links) {

		ret = invoke_bpf(fexit, args_off, retval_off, run_ctx_off, func_meta_off,

				 false, func_meta, cookie_off, ctx);

		if (ret)

			goto out;

	}
@@ -2094,3 +2143,8 @@ bool bpf_jit_inlines_helper_call(s32 imm) 
		return false;

	}

}



bool bpf_jit_supports_fsession(void)

{

	return true;

}