[v3] bpf: fsession support for riscv

[PATCH bpf-next v3 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

Posted by Menglong Dong 2 days, 15 hours ago

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>
Tested-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
---
 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);
 
-- 
2.53.0

Re: [PATCH bpf-next v3 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

Posted by Pu Lehui 2 days, 2 hours ago

On 2026/2/6 20:20, Menglong Dong wrote:
> 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>
> Tested-by: Björn Töpel <bjorn@kernel.org>
> Acked-by: Björn Töpel <bjorn@kernel.org>
> ---
>   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)

Some nit. The first parameter can be removed by using a fixed RV_REG_T1. 
Also, placing imm64 before stack_off might looks better.

> +{
> +	/* 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);
>

Re: [PATCH bpf-next v3 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

Posted by Menglong Dong 1 day, 16 hours ago

On 2026/2/7 09:13, Pu Lehui wrote:
> 
> On 2026/2/6 20:20, Menglong Dong wrote:
> > 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>
> > Tested-by: Björn Töpel <bjorn@kernel.org>
> > Acked-by: Björn Töpel <bjorn@kernel.org>
> > ---
> >   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)
> 
> Some nit. The first parameter can be removed by using a fixed RV_REG_T1. 
> Also, placing imm64 before stack_off might looks better.

Hi, Lehui. When I implement the emit_store_stack_imm64() in x86,
Andrii suggested that we'd better use the register explicitly to indicate
the register is used. So maybe it's better to keep this part still?

I can place the imm64 before stack_off.

Thanks!
Menglong Dong

> 
> > +{
> > +	/* 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);
> >   
> 
>

Re: [PATCH bpf-next v3 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline

Posted by Pu Lehui 1 day, 1 hour ago


On 2026/2/7 18:53, Menglong Dong wrote:
> On 2026/2/7 09:13, Pu Lehui wrote:
>>
>> On 2026/2/6 20:20, Menglong Dong wrote:
>>> 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>
>>> Tested-by: Björn Töpel <bjorn@kernel.org>
>>> Acked-by: Björn Töpel <bjorn@kernel.org>
>>> ---
>>>    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)
>>
>> Some nit. The first parameter can be removed by using a fixed RV_REG_T1.
>> Also, placing imm64 before stack_off might looks better.
> 
> Hi, Lehui. When I implement the emit_store_stack_imm64() in x86,
> Andrii suggested that we'd better use the register explicitly to indicate
> the register is used. So maybe it's better to keep this part still?

No problem, the impact is minimal. And in that case, just leave imm64 
and stack_off as they are. :)

> 
> I can place the imm64 before stack_off.
> 
> Thanks!
> Menglong Dong
> 
>>
>>> +{
>>> +	/* 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);
>>>    
>>
>>
> 
> 
> 
> 
> 
>