[PATCH 0/3] bpf: fsession support for LoongArch

[PATCH 0/3] bpf: fsession support for LoongArch

[Hengqi Chen]

This small set implements fsession support for LoongArch.

Patch 1 introduces a helper named emit_store_stack_imm64().
Patch 2 implements fsession support.
Patch 3 enable fsession selftests on LoongArch.

Hengqi Chen (3):
  LoongArch: BPF: Introduce emit_store_stack_imm64() helper
  LoongArch: BPF: Add fsession support for trampolines
  bpf/selftests: Enable fsession tests for LoongArch

 arch/loongarch/net/bpf_jit.c                  | 100 ++++++++++++++----
 .../selftests/bpf/progs/get_func_args_test.c  |   3 +-
 .../selftests/bpf/progs/get_func_ip_test.c    |   3 +-
 3 files changed, 83 insertions(+), 23 deletions(-)

--
2.43.5

[PATCH 1/3] LoongArch: BPF: Introduce emit_store_stack_imm64() helper

[Hengqi Chen]

Introduce a helper to store 64-bit immediate on the trampoline stack.
The helper will be used in the next patch. Also refactor the existing
code to use this helper.

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 arch/loongarch/net/bpf_jit.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 3bd89f55960d..e3deb0da6a50 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1480,6 +1480,12 @@ static void restore_args(struct jit_ctx *ctx, int nargs, int args_off)
 	}
 }
 
+static void emit_store_stack_imm64(struct jit_ctx *ctx, int reg, int stack_off, u64 imm64)
+{
+	move_imm(ctx, reg, imm64, false);
+	emit_insn(ctx, std, reg, LOONGARCH_GPR_FP, stack_off);
+}
+
 static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
 			   int args_off, int retval_off, int run_ctx_off, bool save_ret)
 {
@@ -1488,12 +1494,11 @@ static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
 	struct bpf_prog *p = l->link.prog;
 	int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
 
-	if (l->cookie) {
-		move_imm(ctx, LOONGARCH_GPR_T1, l->cookie, false);
-		emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -run_ctx_off + cookie_off);
-	} else {
+	if (l->cookie)
+		emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1,
+				      -run_ctx_off + cookie_off, l->cookie);
+	else
 		emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -run_ctx_off + cookie_off);
-	}
 
 	/* arg1: prog */
 	move_imm(ctx, LOONGARCH_GPR_A0, (const s64)p, false);
@@ -1726,14 +1731,11 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 	emit_insn(ctx, std, LOONGARCH_GPR_S1, LOONGARCH_GPR_FP, -sreg_off);
 
 	/* store ip address of the traced function */
-	if (flags & BPF_TRAMP_F_IP_ARG) {
-		move_imm(ctx, LOONGARCH_GPR_T1, (const s64)func_addr, false);
-		emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -ip_off);
-	}
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -ip_off, (u64)func_addr);
 
 	/* store nargs number */
-	move_imm(ctx, LOONGARCH_GPR_T1, nargs, false);
-	emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -nargs_off);
+	emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -nargs_off, nargs);
 
 	store_args(ctx, nargs, args_off);
 
-- 
2.43.5

[PATCH 2/3] LoongArch: BPF: Add fsession support for trampolines

[Hengqi Chen]

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

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 arch/loongarch/net/bpf_jit.c | 78 +++++++++++++++++++++++++++++++-----
 1 file changed, 67 insertions(+), 11 deletions(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index e3deb0da6a50..16da53f80266 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1549,6 +1549,31 @@ 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;
+}
+
 static void invoke_bpf_mod_ret(struct jit_ctx *ctx, struct bpf_tramp_links *tl,
 			       int args_off, int retval_off, int run_ctx_off, u32 **branches)
 {
@@ -1610,13 +1635,15 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 {
 	int i, ret, save_ret;
 	int stack_size, nargs;
-	int retval_off, args_off, nargs_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off;
+	int retval_off, args_off, func_meta_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off;
+	int cookie_off, cookie_cnt;
 	bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT;
 	void *orig_call = func_addr;
 	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];
 	u32 **branches = NULL;
+	u64 func_meta;
 
 	/*
 	 * FP + 8       [ RA to parent func ] return address to parent
@@ -1634,10 +1661,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 	 *                  [ ...               ]
 	 * FP - args_off    [ arg1              ]
 	 *
-	 * FP - nargs_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  ]
@@ -1671,9 +1702,9 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 	stack_size += nargs * 8;
 	args_off = stack_size;
 
-	/* Room of trampoline frame to store args number */
+	/* function metadata, such as regs count */
 	stack_size += 8;
-	nargs_off = stack_size;
+	func_meta_off = stack_size;
 
 	/* Room of trampoline frame to store ip address */
 	if (flags & BPF_TRAMP_F_IP_ARG) {
@@ -1681,6 +1712,11 @@ 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;
@@ -1734,11 +1770,19 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
 	if (flags & BPF_TRAMP_F_IP_ARG)
 		emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -ip_off, (u64)func_addr);
 
-	/* store nargs number */
-	emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -nargs_off, nargs);
+	func_meta = nargs;
+	emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, func_meta);
 
 	store_args(ctx, nargs, 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) ||
@@ -1755,9 +1799,10 @@ 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;
 	}
@@ -1791,8 +1836,14 @@ 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;
 	}
@@ -2132,3 +2183,8 @@ bool bpf_jit_supports_subprog_tailcalls(void)
 {
 	return true;
 }
+
+bool bpf_jit_supports_fsession(void)
+{
+	return true;
+}
-- 
2.43.5

[PATCH bpf-next 3/3] bpf/selftests: Enable fsession tests for LoongArch

[Hengqi Chen]

Now that the LoongArch JIT supports BPF_TRACE_FSESSION, allow
the fsession-related tests to run on LoongArch.

    $ ./test_progs -a fsession_test,get_func_args_test,get_func_ip_test
    #136/1   fsession_test/fsession_test:OK
    #136/2   fsession_test/fsession_reattach:OK
    #136/3   fsession_test/fsession_cookie:OK
    #136     fsession_test:OK
    #138     get_func_args_test:OK
    #139     get_func_ip_test:OK
    Summary: 3/3 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 tools/testing/selftests/bpf/progs/get_func_args_test.c | 3 ++-
 tools/testing/selftests/bpf/progs/get_func_ip_test.c   | 3 ++-
 2 files changed, 4 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 075a1180ec26..afb185fdf60c 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 +167,8 @@ int BPF_PROG(tp_test2)
 }
 
 __u64 test7_result = 0;
-#if defined(bpf_target_x86) || defined(bpf_target_arm64) || defined(bpf_target_riscv)
+#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
+    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
 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 45eaa54d1ac7..3816a3616fbe 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 +106,8 @@ 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) || defined(bpf_target_riscv)
+#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
+    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
 SEC("fsession/bpf_fentry_test1")
 int BPF_PROG(test9, int a)
 {
-- 
2.43.5

Re: [PATCH bpf-next 3/3] bpf/selftests: Enable fsession tests for LoongArch

[Vincent Li]

On Wed, Feb 25, 2026 at 11:00 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> Now that the LoongArch JIT supports BPF_TRACE_FSESSION, allow
> the fsession-related tests to run on LoongArch.
>
>     $ ./test_progs -a fsession_test,get_func_args_test,get_func_ip_test
>     #136/1   fsession_test/fsession_test:OK
>     #136/2   fsession_test/fsession_reattach:OK
>     #136/3   fsession_test/fsession_cookie:OK
>     #136     fsession_test:OK
>     #138     get_func_args_test:OK
>     #139     get_func_ip_test:OK
>     Summary: 3/3 PASSED, 0 SKIPPED, 0 FAILED
>

[root@fedora bpf]# ./test_progs -a
fsession_test,get_func_args_test,get_func_ip_test
#135/1   fsession_test/fsession_test:OK
#135/2   fsession_test/fsession_reattach:OK
#135/3   fsession_test/fsession_cookie:OK
#135     fsession_test:OK
#138     get_func_args_test:OK
#139     get_func_ip_test:OK
Summary: 3/3 PASSED, 0 SKIPPED, 0 FAILED

Tested-by: Vincent Li <vincent.mc.li@gmail.com>

> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>  tools/testing/selftests/bpf/progs/get_func_args_test.c | 3 ++-
>  tools/testing/selftests/bpf/progs/get_func_ip_test.c   | 3 ++-
>  2 files changed, 4 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 075a1180ec26..afb185fdf60c 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 +167,8 @@ int BPF_PROG(tp_test2)
>  }
>
>  __u64 test7_result = 0;
> -#if defined(bpf_target_x86) || defined(bpf_target_arm64) || defined(bpf_target_riscv)
> +#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
> +    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
>  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 45eaa54d1ac7..3816a3616fbe 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 +106,8 @@ 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) || defined(bpf_target_riscv)
> +#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
> +    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
>  SEC("fsession/bpf_fentry_test1")
>  int BPF_PROG(test9, int a)
>  {
> --
> 2.43.5
>

Re: [PATCH bpf-next 3/3] bpf/selftests: Enable fsession tests for LoongArch

[Menglong Dong]

On 2026/2/26 14:59 Hengqi Chen <hengqi.chen@gmail.com> write:
> Now that the LoongArch JIT supports BPF_TRACE_FSESSION, allow
> the fsession-related tests to run on LoongArch.
> 
>     $ ./test_progs -a fsession_test,get_func_args_test,get_func_ip_test
>     #136/1   fsession_test/fsession_test:OK
>     #136/2   fsession_test/fsession_reattach:OK
>     #136/3   fsession_test/fsession_cookie:OK
>     #136     fsession_test:OK
>     #138     get_func_args_test:OK
>     #139     get_func_ip_test:OK
>     Summary: 3/3 PASSED, 0 SKIPPED, 0 FAILED

Hi Hengqi,

The testcases is updated in c1eee8d1e84f "selftests/bpf: factor out
get_func_* tests for fsession", so we don't need the 3rd patch anymore.

Thanks!
Menglong Dong

> 
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>  tools/testing/selftests/bpf/progs/get_func_args_test.c | 3 ++-
>  tools/testing/selftests/bpf/progs/get_func_ip_test.c   | 3 ++-
>  2 files changed, 4 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 075a1180ec26..afb185fdf60c 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 +167,8 @@ int BPF_PROG(tp_test2)
>  }
>  
>  __u64 test7_result = 0;
> -#if defined(bpf_target_x86) || defined(bpf_target_arm64) || defined(bpf_target_riscv)
> +#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
> +    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
>  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 45eaa54d1ac7..3816a3616fbe 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 +106,8 @@ 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) || defined(bpf_target_riscv)
> +#if defined(bpf_target_x86) || defined(bpf_target_arm64) || \
> +    defined(bpf_target_riscv) || defined(bpf_target_loongarch)
>  SEC("fsession/bpf_fentry_test1")
>  int BPF_PROG(test9, int a)
>  {
> -- 
> 2.43.5
> 
> 
> 

Re: [PATCH 1/3] LoongArch: BPF: Introduce emit_store_stack_imm64() helper

[Menglong Dong]

On 2026/2/26 14:59 Hengqi Chen <hengqi.chen@gmail.com> write:
> Introduce a helper to store 64-bit immediate on the trampoline stack.
> The helper will be used in the next patch. Also refactor the existing
> code to use this helper.
> 
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>  arch/loongarch/net/bpf_jit.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index 3bd89f55960d..e3deb0da6a50 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -1480,6 +1480,12 @@ static void restore_args(struct jit_ctx *ctx, int nargs, int args_off)
>  	}
>  }

LGTM.

Reviewed-by: Menglong Dong <menglong8.dong@gmail.com>

>  
> +static void emit_store_stack_imm64(struct jit_ctx *ctx, int reg, int stack_off, u64 imm64)
> +{
> +	move_imm(ctx, reg, imm64, false);
> +	emit_insn(ctx, std, reg, LOONGARCH_GPR_FP, stack_off);
> +}
> +
>  static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>  			   int args_off, int retval_off, int run_ctx_off, bool save_ret)
>  {
> @@ -1488,12 +1494,11 @@ static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>  	struct bpf_prog *p = l->link.prog;
>  	int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
>  
> -	if (l->cookie) {
> -		move_imm(ctx, LOONGARCH_GPR_T1, l->cookie, false);
> -		emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -run_ctx_off + cookie_off);
> -	} else {
> +	if (l->cookie)
> +		emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1,
> +				      -run_ctx_off + cookie_off, l->cookie);
> +	else
>  		emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -run_ctx_off + cookie_off);
> -	}
>  
>  	/* arg1: prog */
>  	move_imm(ctx, LOONGARCH_GPR_A0, (const s64)p, false);
> @@ -1726,14 +1731,11 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
>  	emit_insn(ctx, std, LOONGARCH_GPR_S1, LOONGARCH_GPR_FP, -sreg_off);
>  
>  	/* store ip address of the traced function */
> -	if (flags & BPF_TRAMP_F_IP_ARG) {
> -		move_imm(ctx, LOONGARCH_GPR_T1, (const s64)func_addr, false);
> -		emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -ip_off);
> -	}
> +	if (flags & BPF_TRAMP_F_IP_ARG)
> +		emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -ip_off, (u64)func_addr);
>  
>  	/* store nargs number */
> -	move_imm(ctx, LOONGARCH_GPR_T1, nargs, false);
> -	emit_insn(ctx, std, LOONGARCH_GPR_T1, LOONGARCH_GPR_FP, -nargs_off);
> +	emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -nargs_off, nargs);
>  
>  	store_args(ctx, nargs, args_off);
>  
> -- 
> 2.43.5
> 
> 
> 

Re: [PATCH 2/3] LoongArch: BPF: Add fsession support for trampolines

[Menglong Dong]

On 2026/2/26 14:59 Hengqi Chen <hengqi.chen@gmail.com> write:
> 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
> 
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>  arch/loongarch/net/bpf_jit.c | 78 +++++++++++++++++++++++++++++++-----
>  1 file changed, 67 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index e3deb0da6a50..16da53f80266 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -1549,6 +1549,31 @@ static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>  	return ret;
>  }
>  

LGTM.

Reviewed-by: Menglong Dong <menglong8.dong@gmail.com>

Some nits maybe you can do when you respin the V2 if you don't mind,
see below.

> +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)
> +{
[...]
>  
> +	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) ||
> @@ -1755,9 +1799,10 @@ 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) {

This checking is unnecessary, as invoke_bpf() will return directly
if !fentry->nr_links.

PS: I was told this when I implement the fsession for s390 this way :)


> +		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;
>  	}
> @@ -1791,8 +1836,14 @@ 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) {

And this checking.

Thanks!
Menglong Dong

> +		ret = invoke_bpf(ctx, fexit, args_off, retval_off, run_ctx_off,
> +				 func_meta_off, false, func_meta, cookie_off);
>  		if (ret)
>  			goto out;
>  	}
> @@ -2132,3 +2183,8 @@ bool bpf_jit_supports_subprog_tailcalls(void)
>  {
>  	return true;
>  }
> +
> +bool bpf_jit_supports_fsession(void)
> +{
> +	return true;
> +}
> -- 
> 2.43.5
> 
> 
> 

Re: [PATCH 0/3] bpf: fsession support for LoongArch

[Menglong Dong]

On 2026/2/26 14:59 Hengqi Chen <hengqi.chen@gmail.com> write:
> This small set implements fsession support for LoongArch.
> 
> Patch 1 introduces a helper named emit_store_stack_imm64().
> Patch 2 implements fsession support.
> Patch 3 enable fsession selftests on LoongArch.

I think this series belongs to the bpf-next tree, right? So pls add the
"bpf-next" tag in the next version.

> 
> Hengqi Chen (3):
>   LoongArch: BPF: Introduce emit_store_stack_imm64() helper
>   LoongArch: BPF: Add fsession support for trampolines
>   bpf/selftests: Enable fsession tests for LoongArch
> 
>  arch/loongarch/net/bpf_jit.c                  | 100 ++++++++++++++----
>  .../selftests/bpf/progs/get_func_args_test.c  |   3 +-
>  .../selftests/bpf/progs/get_func_ip_test.c    |   3 +-
>  3 files changed, 83 insertions(+), 23 deletions(-)
> 
> --
> 2.43.5
> 
>