[PATCH bpf-next 0/3] bpf: fsession support for riscv

[PATCH bpf-next 0/3] bpf: fsession support for riscv

[Menglong Dong]

Implement bpf fsession for the riscv architecture.

Menglong Dong (3):
  bpf,riscv: introduce emit_store_stack_imm64() for trampoline
  bpf,riscv: add fsession support for trampolines
  selftests/bpf: enable fsession_test on riscv64

 arch/riscv/net/bpf_jit_comp64.c               | 92 +++++++++++++++----
 .../selftests/bpf/progs/get_func_args_test.c  |  2 +-
 .../selftests/bpf/progs/get_func_ip_test.c    |  2 +-
 3 files changed, 74 insertions(+), 22 deletions(-)

-- 
2.52.0


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[PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

[Menglong Dong]

Introduce a helper to store 64-bit immediate on the trampoline stack with
a help of a register.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
 arch/riscv/net/bpf_jit_comp64.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 37888abee70c..e4f45e2e7e2f 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -926,6 +926,14 @@ static void restore_stack_args(int nr_stack_args, int args_off, int stk_arg_off,
 	}
 }
 
+static void emit_store_stack_imm64(u8 reg, int stack_off, u64 imm64,
+				   struct rv_jit_context *ctx)
+{
+	/* Load imm64 into reg and store it at [FP + stack_off]. */
+	emit_imm(reg, (s64)imm64, ctx);
+	emit_sd(RV_REG_FP, stack_off, reg, ctx);
+}
+
 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)
 {
@@ -933,12 +941,10 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
 	struct bpf_prog *p = l->link.prog;
 	int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
 
-	if (l->cookie) {
-		emit_imm(RV_REG_T1, l->cookie, ctx);
-		emit_sd(RV_REG_FP, -run_ctx_off + cookie_off, RV_REG_T1, ctx);
-	} else {
+	if (l->cookie)
+		emit_store_stack_imm64(RV_REG_T1, -run_ctx_off + cookie_off, l->cookie, ctx);
+	else
 		emit_sd(RV_REG_FP, -run_ctx_off + cookie_off, RV_REG_ZERO, ctx);
-	}
 
 	/* arg1: prog */
 	emit_imm(RV_REG_A0, (const s64)p, ctx);
@@ -1123,13 +1129,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	emit_sd(RV_REG_FP, -sreg_off, RV_REG_S1, ctx);
 
 	/* store ip address of the traced function */
-	if (flags & BPF_TRAMP_F_IP_ARG) {
-		emit_imm(RV_REG_T1, (const s64)func_addr, ctx);
-		emit_sd(RV_REG_FP, -ip_off, RV_REG_T1, ctx);
-	}
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		emit_store_stack_imm64(RV_REG_T1, -ip_off, (u64)func_addr, ctx);
 
-	emit_li(RV_REG_T1, nr_arg_slots, ctx);
-	emit_sd(RV_REG_FP, -nregs_off, RV_REG_T1, ctx);
+	emit_store_stack_imm64(RV_REG_T1, -nregs_off, nr_arg_slots, ctx);
 
 	store_args(nr_arg_slots, args_off, ctx);
 
-- 
2.52.0


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[PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines

[Menglong Dong]

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: Menglong Dong <dongml2@chinatelecom.cn>
---
 arch/riscv/net/bpf_jit_comp64.c | 74 ++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index e4f45e2e7e2f..f10418ff6a9b 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -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 (tl->links[i]->link.prog->call_session_cookie) {
+			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 ]  always
 	 *
 	 * 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;
+}
-- 
2.52.0


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Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines

[Leon Hwang]

On 3/2/26 13:52, Menglong Dong wrote:
> 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: Menglong Dong <dongml2@chinatelecom.cn>
> ---
>  arch/riscv/net/bpf_jit_comp64.c | 74 ++++++++++++++++++++++++++++-----
>  1 file changed, 64 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index e4f45e2e7e2f..f10418ff6a9b 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -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 (tl->links[i]->link.prog->call_session_cookie) {

NIT: we have helper bpf_prog_calls_session_cookie() to read
call_session_cookie.

Thanks,
Leon

> +			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 ]  always
>  	 *
>  	 * 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;
> +}


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Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines

[Menglong Dong]

On 2026/2/3 14:20 Leon Hwang <leon.hwang@linux.dev> write:
> 
> On 3/2/26 13:52, Menglong Dong wrote:
> > 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: Menglong Dong <dongml2@chinatelecom.cn>
> > ---
> >  arch/riscv/net/bpf_jit_comp64.c | 74 ++++++++++++++++++++++++++++-----
> >  1 file changed, 64 insertions(+), 10 deletions(-)
> > 
> > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> > index e4f45e2e7e2f..f10418ff6a9b 100644
> > --- a/arch/riscv/net/bpf_jit_comp64.c
> > +++ b/arch/riscv/net/bpf_jit_comp64.c
> > @@ -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 (tl->links[i]->link.prog->call_session_cookie) {
> 
> NIT: we have helper bpf_prog_calls_session_cookie() to read
> call_session_cookie.

Ah, right, I forget that helper. I'll update it and send the V2 after
getting more feedback.

Thanks!
Menglong Dong

> 
> Thanks,
> Leon
> 
> > +			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 ]  always
> >  	 *
> >  	 * 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;
> > +}
> 
> 
> 





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Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines

[Björn Töpel]

On Tue, 3 Feb 2026 at 06:53, Menglong Dong <menglong8.dong@gmail.com> wrote:

> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index e4f45e2e7e2f..f10418ff6a9b 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c

> @@ -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 ]  always

Nit: Please remove the "always" comment. It's not helpful.

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Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines

[Menglong Dong]

On 2026/2/6 19:22, Björn Töpel wrote:
> On Tue, 3 Feb 2026 at 06:53, Menglong Dong <menglong8.dong@gmail.com> wrote:
> 
> > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> > index e4f45e2e7e2f..f10418ff6a9b 100644
> > --- a/arch/riscv/net/bpf_jit_comp64.c
> > +++ b/arch/riscv/net/bpf_jit_comp64.c
> 
> > @@ -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 ]  always
> 
> Nit: Please remove the "always" comment. It's not helpful.

Ah, sorry that I send out the V2 before I saw this email. Let
me spin a V3.

Thanks!
Menglong Dong

> 
> 





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[PATCH bpf-next 3/3] selftests/bpf: enable fsession_test on riscv64

[Menglong Dong]

Now that the RISC-V trampoline JIT supports BPF_TRACE_FSESSION, run
the fsession selftest on riscv64 as well as x86_64.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
 tools/testing/selftests/bpf/progs/get_func_args_test.c | 2 +-
 tools/testing/selftests/bpf/progs/get_func_ip_test.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/get_func_args_test.c b/tools/testing/selftests/bpf/progs/get_func_args_test.c
index 180ba5098ca1..075a1180ec26 100644
--- a/tools/testing/selftests/bpf/progs/get_func_args_test.c
+++ b/tools/testing/selftests/bpf/progs/get_func_args_test.c
@@ -167,7 +167,7 @@ int BPF_PROG(tp_test2)
 }
 
 __u64 test7_result = 0;
-#if defined(bpf_target_x86) || defined(bpf_target_arm64)
+#if defined(bpf_target_x86) || defined(bpf_target_arm64) || defined(bpf_target_riscv)
 SEC("fsession/bpf_fentry_test1")
 int BPF_PROG(test7)
 {
diff --git a/tools/testing/selftests/bpf/progs/get_func_ip_test.c b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
index 43ff836a8ed8..45eaa54d1ac7 100644
--- a/tools/testing/selftests/bpf/progs/get_func_ip_test.c
+++ b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
@@ -106,7 +106,7 @@ int BPF_URETPROBE(test8, int ret)
 
 __u64 test9_entry_result = 0;
 __u64 test9_exit_result = 0;
-#if defined(bpf_target_x86) || defined(bpf_target_arm64)
+#if defined(bpf_target_x86) || defined(bpf_target_arm64) || defined(bpf_target_riscv)
 SEC("fsession/bpf_fentry_test1")
 int BPF_PROG(test9, int a)
 {
-- 
2.52.0


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Re: [PATCH bpf-next 0/3] bpf: fsession support for riscv

[Björn Töpel]

Thank you for working on this!

On Tue, 3 Feb 2026 at 06:52, Menglong Dong <menglong8.dong@gmail.com> wrote:
>
> Implement bpf fsession for the riscv architecture.
>
> Menglong Dong (3):
>   bpf,riscv: introduce emit_store_stack_imm64() for trampoline
>   bpf,riscv: add fsession support for trampolines
>   selftests/bpf: enable fsession_test on riscv64

I'm happy with either addressing Leon's comment with a follow-up, or
spinning a V2.

For this version plus Leon's nit as a follow-up, or a V2:
Tested-by: Björn Töpel <bjorn@kernel.org> # QEMU/RVA23/DT
Acked-by: Björn Töpel <bjorn@kernel.org>

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Re: [PATCH bpf-next 0/3] bpf: fsession support for riscv

[Menglong Dong]

On 2026/2/6 19:20, Björn Töpel wrote:
> Thank you for working on this!
> 
> On Tue, 3 Feb 2026 at 06:52, Menglong Dong <menglong8.dong@gmail.com> wrote:
> >
> > Implement bpf fsession for the riscv architecture.
> >
> > Menglong Dong (3):
> >   bpf,riscv: introduce emit_store_stack_imm64() for trampoline
> >   bpf,riscv: add fsession support for trampolines
> >   selftests/bpf: enable fsession_test on riscv64
> 
> I'm happy with either addressing Leon's comment with a follow-up, or
> spinning a V2.
> 
> For this version plus Leon's nit as a follow-up, or a V2:
> Tested-by: Björn Töpel <bjorn@kernel.org> # QEMU/RVA23/DT
> Acked-by: Björn Töpel <bjorn@kernel.org>

Hi, Björn. Thanks for your reviewing and testing. I'll send a V2
now :)

> 
> 





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