* [PATCH bpf-next 0/3] bpf: fsession support for riscv
@ 2026-02-03 5:52 Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline Menglong Dong
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-03 5:52 UTC (permalink / raw)
To: ast
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline
2026-02-03 5:52 [PATCH bpf-next 0/3] bpf: fsession support for riscv Menglong Dong
@ 2026-02-03 5:52 ` Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines Menglong Dong
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-03 5:52 UTC (permalink / raw)
To: ast
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines
2026-02-03 5:52 [PATCH bpf-next 0/3] bpf: fsession support for riscv Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline Menglong Dong
@ 2026-02-03 5:52 ` Menglong Dong
2026-02-03 6:20 ` Leon Hwang
2026-02-06 11:22 ` Björn Töpel
2026-02-03 5:52 ` [PATCH bpf-next 3/3] selftests/bpf: enable fsession_test on riscv64 Menglong Dong
2026-02-06 11:20 ` [PATCH bpf-next 0/3] bpf: fsession support for riscv Björn Töpel
3 siblings, 2 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-03 5:52 UTC (permalink / raw)
To: ast
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH bpf-next 3/3] selftests/bpf: enable fsession_test on riscv64
2026-02-03 5:52 [PATCH bpf-next 0/3] bpf: fsession support for riscv Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines Menglong Dong
@ 2026-02-03 5:52 ` Menglong Dong
2026-02-06 11:20 ` [PATCH bpf-next 0/3] bpf: fsession support for riscv Björn Töpel
3 siblings, 0 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-03 5:52 UTC (permalink / raw)
To: ast
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines
2026-02-03 5:52 ` [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines Menglong Dong
@ 2026-02-03 6:20 ` Leon Hwang
2026-02-03 6:25 ` Menglong Dong
2026-02-06 11:22 ` Björn Töpel
1 sibling, 1 reply; 10+ messages in thread
From: Leon Hwang @ 2026-02-03 6:20 UTC (permalink / raw)
To: Menglong Dong, ast
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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;
> +}
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines
2026-02-03 6:20 ` Leon Hwang
@ 2026-02-03 6:25 ` Menglong Dong
0 siblings, 0 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-03 6:25 UTC (permalink / raw)
To: Menglong Dong, ast, Leon Hwang
Cc: daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, bjorn, pulehui,
puranjay, pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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;
> > +}
>
>
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 0/3] bpf: fsession support for riscv
2026-02-03 5:52 [PATCH bpf-next 0/3] bpf: fsession support for riscv Menglong Dong
` (2 preceding siblings ...)
2026-02-03 5:52 ` [PATCH bpf-next 3/3] selftests/bpf: enable fsession_test on riscv64 Menglong Dong
@ 2026-02-06 11:20 ` Björn Töpel
2026-02-06 11:29 ` Menglong Dong
3 siblings, 1 reply; 10+ messages in thread
From: Björn Töpel @ 2026-02-06 11:20 UTC (permalink / raw)
To: Menglong Dong
Cc: ast, daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, pulehui, puranjay,
pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel, Leon Hwang
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>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines
2026-02-03 5:52 ` [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines Menglong Dong
2026-02-03 6:20 ` Leon Hwang
@ 2026-02-06 11:22 ` Björn Töpel
2026-02-06 12:07 ` Menglong Dong
1 sibling, 1 reply; 10+ messages in thread
From: Björn Töpel @ 2026-02-06 11:22 UTC (permalink / raw)
To: Menglong Dong
Cc: ast, daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, pulehui, puranjay,
pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 0/3] bpf: fsession support for riscv
2026-02-06 11:20 ` [PATCH bpf-next 0/3] bpf: fsession support for riscv Björn Töpel
@ 2026-02-06 11:29 ` Menglong Dong
0 siblings, 0 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-06 11:29 UTC (permalink / raw)
To: Menglong Dong, Björn Töpel
Cc: ast, daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, pulehui, puranjay,
pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel, Leon Hwang
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 :)
>
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines
2026-02-06 11:22 ` Björn Töpel
@ 2026-02-06 12:07 ` Menglong Dong
0 siblings, 0 replies; 10+ messages in thread
From: Menglong Dong @ 2026-02-06 12:07 UTC (permalink / raw)
To: Menglong Dong, Björn Töpel
Cc: ast, daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, pulehui, puranjay,
pjw, palmer, aou, alex, jiang.biao, bpf, linux-riscv,
linux-kernel
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
>
>
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2026-02-06 12:08 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-02-03 5:52 [PATCH bpf-next 0/3] bpf: fsession support for riscv Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 1/3] bpf, riscv: introduce emit_store_stack_imm64() for trampoline Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 2/3] bpf, riscv: add fsession support for trampolines Menglong Dong
2026-02-03 6:20 ` Leon Hwang
2026-02-03 6:25 ` Menglong Dong
2026-02-06 11:22 ` Björn Töpel
2026-02-06 12:07 ` Menglong Dong
2026-02-03 5:52 ` [PATCH bpf-next 3/3] selftests/bpf: enable fsession_test on riscv64 Menglong Dong
2026-02-06 11:20 ` [PATCH bpf-next 0/3] bpf: fsession support for riscv Björn Töpel
2026-02-06 11:29 ` Menglong Dong
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