* [PATCH v2 0/2] Fix two tailcall-related issues
@ 2025-07-08 7:18 Haoran Jiang
2025-07-08 7:18 ` [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function Haoran Jiang
2025-07-08 7:18 ` [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy Haoran Jiang
0 siblings, 2 replies; 7+ messages in thread
From: Haoran Jiang @ 2025-07-08 7:18 UTC (permalink / raw)
To: loongarch
Cc: bpf, kernel, chenhuacai, hengqi.chen, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
v2:
1,Add a Fixes tag.
2,Ctx as the first parameter of emit_bpf_tail_call.
3,Define jmp_offset as a macro in emit_bpf_tail_call.
After merging these two patches, the test results are as follows:
./test_progs --allow=tailcalls
tester_init:PASS:tester_log_buf 0 nsec
process_subtest:PASS:obj_open_mem 0 nsec
process_subtest:PASS:specs_alloc 0 nsec
#413/1 tailcalls/tailcall_1:OK
#413/2 tailcalls/tailcall_2:OK
#413/3 tailcalls/tailcall_3:OK
#413/4 tailcalls/tailcall_4:OK
#413/5 tailcalls/tailcall_5:OK
#413/6 tailcalls/tailcall_6:OK
#413/7 tailcalls/tailcall_bpf2bpf_1:OK
#413/8 tailcalls/tailcall_bpf2bpf_2:OK
#413/9 tailcalls/tailcall_bpf2bpf_3:OK
#413/10 tailcalls/tailcall_bpf2bpf_4:OK
#413/11 tailcalls/tailcall_bpf2bpf_5:OK
#413/12 tailcalls/tailcall_bpf2bpf_6:OK
test_tailcall_count:PASS:open fentry_obj file 0 nsec
test_tailcall_count:PASS:find fentry prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/13 tailcalls/tailcall_bpf2bpf_fentry:FAIL
test_tailcall_count:PASS:open fexit_obj file 0 nsec
test_tailcall_count:PASS:find fexit prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fexit_obj 0 nsec
libbpf: prog 'fexit': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/14 tailcalls/tailcall_bpf2bpf_fexit:FAIL
test_tailcall_count:PASS:open fentry_obj file 0 nsec
test_tailcall_count:PASS:find fentry prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:FAIL
test_tailcall_bpf2bpf_fentry_entry:PASS:load tgt_obj 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find jmp_table map 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find jmp_table map fd 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find classifier_0 prog 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find classifier_0 prog fd 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:update jmp_table 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:open fentry_obj file 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find fentry prog 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:set_attach_target classifier_0 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_bpf2bpf_fentry_entry:FAIL:attach_trace unexpected error: -524
#413/16 tailcalls/tailcall_bpf2bpf_fentry_entry:FAIL
#413/17 tailcalls/tailcall_poke:OK
#413/18 tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/19 tailcalls/tailcall_bpf2bpf_hierarchy_fentry:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fexit_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fexit prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fexit_obj 0 nsec
libbpf: prog 'fexit': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/20 tailcalls/tailcall_bpf2bpf_hierarchy_fexit:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/21 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target entry 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
tester_init:PASS:tester_log_buf 0 nsec
process_subtest:PASS:obj_open_mem 0 nsec
process_subtest:PASS:specs_alloc 0 nsec
#413/22 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:FAIL
#413/23 tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
#413/24 tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
test_tailcall_freplace:PASS:tailcall_freplace__open 0 nsec
test_tailcall_freplace:PASS:tc_bpf2bpf__open_and_load 0 nsec
test_tailcall_freplace:PASS:set_attach_target 0 nsec
test_tailcall_freplace:PASS:tailcall_freplace__load 0 nsec
test_tailcall_freplace:PASS:update jmp_table failure 0 nsec
libbpf: prog 'entry_freplace': failed to attach to freplace: -ENOTSUPP
test_tailcall_freplace:FAIL:attach_freplace unexpected error: -524
#413/25 tailcalls/tailcall_freplace:FAIL
test_tailcall_bpf2bpf_freplace:PASS:tc_bpf2bpf__open_and_load 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:tailcall_freplace__open 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:set_attach_target 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:tailcall_freplace__load 0 nsec
libbpf: prog 'entry_freplace': failed to attach to freplace: -ENOTSUPP
test_tailcall_bpf2bpf_freplace:FAIL:attach_freplace unexpected error: -524
#413/26 tailcalls/tailcall_bpf2bpf_freplace:FAIL
#413/27 tailcalls/tailcall_failure:OK
#413/28 tailcalls/reject_tail_call_spin_lock:OK
#413/29 tailcalls/reject_tail_call_rcu_lock:OK
#413/30 tailcalls/reject_tail_call_preempt_lock:OK
#413/31 tailcalls/reject_tail_call_ref:OK
#413 tailcalls:FAIL
All error logs:
tester_init:PASS:tester_log_buf 0 nsec
process_subtest:PASS:obj_open_mem 0 nsec
process_subtest:PASS:specs_alloc 0 nsec
test_tailcall_count:PASS:open fentry_obj file 0 nsec
test_tailcall_count:PASS:find fentry prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/13 tailcalls/tailcall_bpf2bpf_fentry:FAIL
test_tailcall_count:PASS:open fexit_obj file 0 nsec
test_tailcall_count:PASS:find fexit prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fexit_obj 0 nsec
libbpf: prog 'fexit': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/14 tailcalls/tailcall_bpf2bpf_fexit:FAIL
test_tailcall_count:PASS:open fentry_obj file 0 nsec
test_tailcall_count:PASS:find fentry prog 0 nsec
test_tailcall_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_count:FAIL:attach_trace unexpected error: -524
#413/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:FAIL
test_tailcall_bpf2bpf_fentry_entry:PASS:load tgt_obj 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find jmp_table map 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find jmp_table map fd 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find classifier_0 prog 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find classifier_0 prog fd 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:update jmp_table 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:open fentry_obj file 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:find fentry prog 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:set_attach_target classifier_0 0 nsec
test_tailcall_bpf2bpf_fentry_entry:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_bpf2bpf_fentry_entry:FAIL:attach_trace unexpected error: -524
#413/16 tailcalls/tailcall_bpf2bpf_fentry_entry:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/19 tailcalls/tailcall_bpf2bpf_hierarchy_fentry:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fexit_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fexit prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fexit_obj 0 nsec
libbpf: prog 'fexit': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/20 tailcalls/tailcall_bpf2bpf_hierarchy_fexit:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:find jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:map_fd 0 nsec
test_tailcall_hierarchy_count:PASS:update jmp_table 0 nsec
test_tailcall_hierarchy_count:PASS:find data_map 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target subprog_tail 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
#413/21 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:FAIL
test_tailcall_hierarchy_count:PASS:load obj 0 nsec
test_tailcall_hierarchy_count:PASS:find entry prog 0 nsec
test_tailcall_hierarchy_count:PASS:prog_fd 0 nsec
test_tailcall_hierarchy_count:PASS:open fentry_obj file 0 nsec
test_tailcall_hierarchy_count:PASS:find fentry prog 0 nsec
test_tailcall_hierarchy_count:PASS:set_attach_target entry 0 nsec
test_tailcall_hierarchy_count:PASS:load fentry_obj 0 nsec
libbpf: prog 'fentry': failed to attach: -ENOTSUPP
test_tailcall_hierarchy_count:FAIL:attach_trace unexpected error: -524
tester_init:PASS:tester_log_buf 0 nsec
process_subtest:PASS:obj_open_mem 0 nsec
process_subtest:PASS:specs_alloc 0 nsec
#413/22 tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:FAIL
test_tailcall_freplace:PASS:tailcall_freplace__open 0 nsec
test_tailcall_freplace:PASS:tc_bpf2bpf__open_and_load 0 nsec
test_tailcall_freplace:PASS:set_attach_target 0 nsec
test_tailcall_freplace:PASS:tailcall_freplace__load 0 nsec
test_tailcall_freplace:PASS:update jmp_table failure 0 nsec
libbpf: prog 'entry_freplace': failed to attach to freplace: -ENOTSUPP
test_tailcall_freplace:FAIL:attach_freplace unexpected error: -524
#413/25 tailcalls/tailcall_freplace:FAIL
test_tailcall_bpf2bpf_freplace:PASS:tc_bpf2bpf__open_and_load 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:tailcall_freplace__open 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:set_attach_target 0 nsec
test_tailcall_bpf2bpf_freplace:PASS:tailcall_freplace__load 0 nsec
libbpf: prog 'entry_freplace': failed to attach to freplace: -ENOTSUPP
test_tailcall_bpf2bpf_freplace:FAIL:attach_freplace unexpected error: -524
#413/26 tailcalls/tailcall_bpf2bpf_freplace:FAIL
#413 tailcalls:FAIL
Summary: 0/21 PASSED, 0 SKIPPED, 1 FAILED
----------------------------------------------------------------------
v1:
1,Fix the jmp_offset calculation error in the emit_bpf_tail_call function.
2,Fix the issue that MAX_TAIL_CALL_CNT limit bypass in hybrid tailcall and BPF-to-BPF call
After applying this patch, testing results are as follows:
./test_progs --allow=tailcalls/tailcall_bpf2bpf_hierarchy_1
413/18 tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
413 tailcalls:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
./test_progs --allow=tailcalls/tailcall_bpf2bpf_hierarchy_2
413/23 tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
413 tailcalls:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
./test_progs --allow=tailcalls/tailcall_bpf2bpf_hierarchy_3
413/24 tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
413 tailcalls:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
Haoran Jiang (2):
LoongArch: BPF: Optimize the calculation method of jmp_offset in the
emit_bpf_tail_call function
LoongArch: BPF: Fix tailcall hierarchy
arch/loongarch/net/bpf_jit.c | 133 +++++++++++++++++++----------------
1 file changed, 74 insertions(+), 59 deletions(-)
--
2.43.0
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function
2025-07-08 7:18 [PATCH v2 0/2] Fix two tailcall-related issues Haoran Jiang
@ 2025-07-08 7:18 ` Haoran Jiang
2025-07-16 1:31 ` Hengqi Chen
2025-07-08 7:18 ` [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy Haoran Jiang
1 sibling, 1 reply; 7+ messages in thread
From: Haoran Jiang @ 2025-07-08 7:18 UTC (permalink / raw)
To: loongarch
Cc: bpf, kernel, chenhuacai, hengqi.chen, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
The extra pass of bpf_int_jit_compile() skips JIT context initialization
which essentially skips offset calculation leaving out_offset = -1,
the jmp_offset in emit_bpf_tail_call is calculated
by #define jmp_offset (out_offset - (cur_offset)) is a negative number,
which does not meet expectations.The final generated assembly as follow.
54: bgeu $a2, $t1, -8 # 0x0000004c
58: addi.d $a6, $s5, -1
5c: bltz $a6, -16 # 0x0000004c
60: alsl.d $t2, $a2, $a1, 0x3
64: ld.d $t2, $t2, 264
68: beq $t2, $zero, -28 # 0x0000004c
Before apply this patch, the follow test case will reveal soft lock issues.
cd tools/testing/selftests/bpf/
./test_progs --allow=tailcalls/tailcall_bpf2bpf_1
dmesg:
watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
---
arch/loongarch/net/bpf_jit.c | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index fa1500d4aa3e..5061bfc978f2 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -208,9 +208,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
return true;
}
-/* initialized on the first pass of build_body() */
-static int out_offset = -1;
-static int emit_bpf_tail_call(struct jit_ctx *ctx)
+static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
{
int off;
u8 tcc = tail_call_reg(ctx);
@@ -220,9 +218,10 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
u8 t2 = LOONGARCH_GPR_T2;
u8 t3 = LOONGARCH_GPR_T3;
const int idx0 = ctx->idx;
+ int tc_ninsn = 0;
#define cur_offset (ctx->idx - idx0)
-#define jmp_offset (out_offset - (cur_offset))
+#define jmp_offset (tc_ninsn - (cur_offset))
/*
* a0: &ctx
@@ -232,6 +231,8 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
* if (index >= array->map.max_entries)
* goto out;
*/
+ tc_ninsn = insn ? ctx->offset[insn+1] - ctx->offset[insn] :
+ ctx->offset[0];
off = offsetof(struct bpf_array, map.max_entries);
emit_insn(ctx, ldwu, t1, a1, off);
/* bgeu $a2, $t1, jmp_offset */
@@ -263,15 +264,6 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
emit_insn(ctx, ldd, t3, t2, off);
__build_epilogue(ctx, true);
- /* out: */
- if (out_offset == -1)
- out_offset = cur_offset;
- if (cur_offset != out_offset) {
- pr_err_once("tail_call out_offset = %d, expected %d!\n",
- cur_offset, out_offset);
- return -1;
- }
-
return 0;
toofar:
@@ -916,7 +908,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
/* tail call */
case BPF_JMP | BPF_TAIL_CALL:
mark_tail_call(ctx);
- if (emit_bpf_tail_call(ctx) < 0)
+ if (emit_bpf_tail_call(ctx, i) < 0)
return -EINVAL;
break;
@@ -1342,7 +1334,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ? tmp : orig_prog);
- out_offset = -1;
return prog;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy
2025-07-08 7:18 [PATCH v2 0/2] Fix two tailcall-related issues Haoran Jiang
2025-07-08 7:18 ` [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function Haoran Jiang
@ 2025-07-08 7:18 ` Haoran Jiang
2025-07-16 2:28 ` Hengqi Chen
1 sibling, 1 reply; 7+ messages in thread
From: Haoran Jiang @ 2025-07-08 7:18 UTC (permalink / raw)
To: loongarch
Cc: bpf, kernel, chenhuacai, hengqi.chen, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
In specific use cases combining tailcalls and BPF-to-BPF calls，
MAX_TAIL_CALL_CNT won't work because of missing tail_call_cnt
back-propagation from callee to caller。This patch fixes this
tailcall issue caused by abusing the tailcall in bpf2bpf feature
on LoongArch like the way of "bpf, x64: Fix tailcall hierarchy".
push tail_call_cnt_ptr and tail_call_cnt into the stack,
tail_call_cnt_ptr is passed between tailcall and bpf2bpf,
uses tail_call_cnt_ptr to increment tail_call_cnt.
Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf and tailcalls")
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
---
arch/loongarch/net/bpf_jit.c | 112 +++++++++++++++++++++--------------
1 file changed, 68 insertions(+), 44 deletions(-)
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 5061bfc978f2..45f804b7c556 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -7,10 +7,9 @@
#include "bpf_jit.h"
#define REG_TCC LOONGARCH_GPR_A6
-#define TCC_SAVED LOONGARCH_GPR_S5
-#define SAVE_RA BIT(0)
-#define SAVE_TCC BIT(1)
+#define BPF_TAIL_CALL_CNT_PTR_STACK_OFF(stack) (round_up(stack, 16) - 80)
+
static const int regmap[] = {
/* return value from in-kernel function, and exit value for eBPF program */
@@ -32,32 +31,37 @@ static const int regmap[] = {
[BPF_REG_AX] = LOONGARCH_GPR_T0,
};
-static void mark_call(struct jit_ctx *ctx)
+static void prepare_bpf_tail_call_cnt(struct jit_ctx *ctx, int *store_offset)
{
- ctx->flags |= SAVE_RA;
-}
+ const struct bpf_prog *prog = ctx->prog;
+ const bool is_main_prog = !bpf_is_subprog(prog);
-static void mark_tail_call(struct jit_ctx *ctx)
-{
- ctx->flags |= SAVE_TCC;
-}
+ if (is_main_prog) {
+ emit_insn(ctx, addid, LOONGARCH_GPR_T3, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
+ *store_offset -= sizeof(long);
-static bool seen_call(struct jit_ctx *ctx)
-{
- return (ctx->flags & SAVE_RA);
-}
+ emit_tailcall_jmp(ctx, BPF_JGT, REG_TCC, LOONGARCH_GPR_T3, 4);
-static bool seen_tail_call(struct jit_ctx *ctx)
-{
- return (ctx->flags & SAVE_TCC);
-}
+ /* If REG_TCC < MAX_TAIL_CALL_CNT, push REG_TCC into stack */
+ emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
-static u8 tail_call_reg(struct jit_ctx *ctx)
-{
- if (seen_call(ctx))
- return TCC_SAVED;
+ /* Calculate the pointer to REG_TCC in the stack and assign it to REG_TCC */
+ emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
+
+ emit_uncond_jmp(ctx, 2);
+
+ emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
- return REG_TCC;
+ *store_offset -= sizeof(long);
+ emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
+
+ } else {
+ *store_offset -= sizeof(long);
+ emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
+
+ *store_offset -= sizeof(long);
+ emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
+ }
}
/*
@@ -80,6 +84,10 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
* | $s4 |
* +-------------------------+
* | $s5 |
+ * +-------------------------+
+ * | reg_tcc |
+ * +-------------------------+
+ * | reg_tcc_ptr |
* +-------------------------+ <--BPF_REG_FP
* | prog->aux->stack_depth |
* | (optional) |
@@ -89,21 +97,24 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
static void build_prologue(struct jit_ctx *ctx)
{
int stack_adjust = 0, store_offset, bpf_stack_adjust;
+ const struct bpf_prog *prog = ctx->prog;
+ const bool is_main_prog = !bpf_is_subprog(prog);
bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
- /* To store ra, fp, s0, s1, s2, s3, s4 and s5. */
- stack_adjust += sizeof(long) * 8;
+ /* To store ra, fp, s0, s1, s2, s3, s4, s5, reg_tcc and reg_tcc_ptr */
+ stack_adjust += sizeof(long) * 10;
stack_adjust = round_up(stack_adjust, 16);
stack_adjust += bpf_stack_adjust;
/*
- * First instruction initializes the tail call count (TCC).
- * On tail call we skip this instruction, and the TCC is
+ * First instruction initializes the tail call count (TCC) register
+ * to zero. On tail call we skip this instruction, and the TCC is
* passed in REG_TCC from the caller.
*/
- emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
+ if (is_main_prog)
+ emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, 0);
emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_adjust);
@@ -131,20 +142,13 @@ static void build_prologue(struct jit_ctx *ctx)
store_offset -= sizeof(long);
emit_insn(ctx, std, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, store_offset);
+ prepare_bpf_tail_call_cnt(ctx, &store_offset);
+
emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_adjust);
if (bpf_stack_adjust)
emit_insn(ctx, addid, regmap[BPF_REG_FP], LOONGARCH_GPR_SP, bpf_stack_adjust);
- /*
- * Program contains calls and tail calls, so REG_TCC need
- * to be saved across calls.
- */
- if (seen_tail_call(ctx) && seen_call(ctx))
- move_reg(ctx, TCC_SAVED, REG_TCC);
- else
- emit_insn(ctx, nop);
-
ctx->stack_size = stack_adjust;
}
@@ -177,6 +181,17 @@ static void __build_epilogue(struct jit_ctx *ctx, bool is_tail_call)
load_offset -= sizeof(long);
emit_insn(ctx, ldd, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, load_offset);
+ /*
+ * When push into the stack, follow the order of tcc then tcc_ptr.
+ * When pop from the stack, first pop tcc_ptr followed by tcc
+ */
+ load_offset -= 2*sizeof(long);
+ emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
+
+ /* pop tcc_ptr to REG_TCC */
+ load_offset += sizeof(long);
+ emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
+
emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_adjust);
if (!is_tail_call) {
@@ -211,7 +226,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
{
int off;
- u8 tcc = tail_call_reg(ctx);
+ int tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
u8 a1 = LOONGARCH_GPR_A1;
u8 a2 = LOONGARCH_GPR_A2;
u8 t1 = LOONGARCH_GPR_T1;
@@ -240,11 +255,15 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
goto toofar;
/*
- * if (--TCC < 0)
- * goto out;
+ * if ((*tcc_ptr)++ >= MAX_TAIL_CALL_CNT)
+ * goto out;
*/
- emit_insn(ctx, addid, REG_TCC, tcc, -1);
- if (emit_tailcall_jmp(ctx, BPF_JSLT, REG_TCC, LOONGARCH_GPR_ZERO, jmp_offset) < 0)
+ emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
+ emit_insn(ctx, ldd, t3, REG_TCC, 0);
+ emit_insn(ctx, addid, t3, t3, 1);
+ emit_insn(ctx, std, t3, REG_TCC, 0);
+ emit_insn(ctx, addid, t2, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
+ if (emit_tailcall_jmp(ctx, BPF_JSGT, t3, t2, jmp_offset) < 0)
goto toofar;
/*
@@ -465,6 +484,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
const s16 off = insn->off;
const s32 imm = insn->imm;
const bool is32 = BPF_CLASS(insn->code) == BPF_ALU || BPF_CLASS(insn->code) == BPF_JMP32;
+ int tcc_ptr_off;
switch (code) {
/* dst = src */
@@ -891,12 +911,17 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
/* function call */
case BPF_JMP | BPF_CALL:
- mark_call(ctx);
ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
&func_addr, &func_addr_fixed);
if (ret < 0)
return ret;
+ if (insn->src_reg == BPF_PSEUDO_CALL) {
+ tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
+ emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
+ }
+
+
move_addr(ctx, t1, func_addr);
emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0);
@@ -907,7 +932,6 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
/* tail call */
case BPF_JMP | BPF_TAIL_CALL:
- mark_tail_call(ctx);
if (emit_bpf_tail_call(ctx, i) < 0)
return -EINVAL;
break;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function
2025-07-08 7:18 ` [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function Haoran Jiang
@ 2025-07-16 1:31 ` Hengqi Chen
2025-07-22 9:34 ` re：[PATCH " jianghaoran
0 siblings, 1 reply; 7+ messages in thread
From: Hengqi Chen @ 2025-07-16 1:31 UTC (permalink / raw)
To: Haoran Jiang
Cc: loongarch, bpf, kernel, chenhuacai, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
Hi Haoran,
On Tue, Jul 8, 2025 at 3:19 PM Haoran Jiang <jianghaoran@kylinos.cn> wrote:
>
> The extra pass of bpf_int_jit_compile() skips JIT context initialization
> which essentially skips offset calculation leaving out_offset = -1,
> the jmp_offset in emit_bpf_tail_call is calculated
> by #define jmp_offset (out_offset - (cur_offset)) is a negative number,
> which does not meet expectations.The final generated assembly as follow.
>
"does not meet expectations" ? Simply "is wrong" ?
The subject line should be something like:
Fix jump offset calculation in tailcall
It's a fix, not optimization.
Other than that, feel free to add:
Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
> 54: bgeu $a2, $t1, -8 # 0x0000004c
> 58: addi.d $a6, $s5, -1
> 5c: bltz $a6, -16 # 0x0000004c
> 60: alsl.d $t2, $a2, $a1, 0x3
> 64: ld.d $t2, $t2, 264
> 68: beq $t2, $zero, -28 # 0x0000004c
>
> Before apply this patch, the follow test case will reveal soft lock issues.
>
> cd tools/testing/selftests/bpf/
> ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1
>
> dmesg:
> watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]
>
> Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
> Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
> ---
> arch/loongarch/net/bpf_jit.c | 21 ++++++---------------
> 1 file changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index fa1500d4aa3e..5061bfc978f2 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -208,9 +208,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
> return true;
> }
>
> -/* initialized on the first pass of build_body() */
> -static int out_offset = -1;
> -static int emit_bpf_tail_call(struct jit_ctx *ctx)
> +static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> {
> int off;
> u8 tcc = tail_call_reg(ctx);
> @@ -220,9 +218,10 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
> u8 t2 = LOONGARCH_GPR_T2;
> u8 t3 = LOONGARCH_GPR_T3;
> const int idx0 = ctx->idx;
> + int tc_ninsn = 0;
>
> #define cur_offset (ctx->idx - idx0)
> -#define jmp_offset (out_offset - (cur_offset))
> +#define jmp_offset (tc_ninsn - (cur_offset))
>
> /*
> * a0: &ctx
> @@ -232,6 +231,8 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
> * if (index >= array->map.max_entries)
> * goto out;
> */
> + tc_ninsn = insn ? ctx->offset[insn+1] - ctx->offset[insn] :
> + ctx->offset[0];
> off = offsetof(struct bpf_array, map.max_entries);
> emit_insn(ctx, ldwu, t1, a1, off);
> /* bgeu $a2, $t1, jmp_offset */
> @@ -263,15 +264,6 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
> emit_insn(ctx, ldd, t3, t2, off);
> __build_epilogue(ctx, true);
>
> - /* out: */
> - if (out_offset == -1)
> - out_offset = cur_offset;
> - if (cur_offset != out_offset) {
> - pr_err_once("tail_call out_offset = %d, expected %d!\n",
> - cur_offset, out_offset);
> - return -1;
> - }
> -
> return 0;
>
> toofar:
> @@ -916,7 +908,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> /* tail call */
> case BPF_JMP | BPF_TAIL_CALL:
> mark_tail_call(ctx);
> - if (emit_bpf_tail_call(ctx) < 0)
> + if (emit_bpf_tail_call(ctx, i) < 0)
> return -EINVAL;
> break;
>
> @@ -1342,7 +1334,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> if (tmp_blinded)
> bpf_jit_prog_release_other(prog, prog == orig_prog ? tmp : orig_prog);
>
> - out_offset = -1;
>
> return prog;
>
> --
> 2.43.0
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy
2025-07-08 7:18 ` [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy Haoran Jiang
@ 2025-07-16 2:28 ` Hengqi Chen
2025-07-22 9:56 ` re：[PATCH " jianghaoran
0 siblings, 1 reply; 7+ messages in thread
From: Hengqi Chen @ 2025-07-16 2:28 UTC (permalink / raw)
To: Haoran Jiang
Cc: loongarch, bpf, kernel, chenhuacai, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
On Tue, Jul 8, 2025 at 3:19 PM Haoran Jiang <jianghaoran@kylinos.cn> wrote:
>
> In specific use cases combining tailcalls and BPF-to-BPF calls，
> MAX_TAIL_CALL_CNT won't work because of missing tail_call_cnt
> back-propagation from callee to caller。This patch fixes this
> tailcall issue caused by abusing the tailcall in bpf2bpf feature
> on LoongArch like the way of "bpf, x64: Fix tailcall hierarchy".
>
> push tail_call_cnt_ptr and tail_call_cnt into the stack,
> tail_call_cnt_ptr is passed between tailcall and bpf2bpf,
> uses tail_call_cnt_ptr to increment tail_call_cnt.
>
> Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf and tailcalls")
> Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
> Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
> ---
> arch/loongarch/net/bpf_jit.c | 112 +++++++++++++++++++++--------------
> 1 file changed, 68 insertions(+), 44 deletions(-)
>
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index 5061bfc978f2..45f804b7c556 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -7,10 +7,9 @@
> #include "bpf_jit.h"
>
> #define REG_TCC LOONGARCH_GPR_A6
> -#define TCC_SAVED LOONGARCH_GPR_S5
>
> -#define SAVE_RA BIT(0)
> -#define SAVE_TCC BIT(1)
> +#define BPF_TAIL_CALL_CNT_PTR_STACK_OFF(stack) (round_up(stack, 16) - 80)
> +
>
> static const int regmap[] = {
> /* return value from in-kernel function, and exit value for eBPF program */
> @@ -32,32 +31,37 @@ static const int regmap[] = {
> [BPF_REG_AX] = LOONGARCH_GPR_T0,
> };
>
> -static void mark_call(struct jit_ctx *ctx)
> +static void prepare_bpf_tail_call_cnt(struct jit_ctx *ctx, int *store_offset)
Consider adding more comments(e.g. pseudocode) for prepare_bpf_tail_call_cnt().
Assembly is hard to read. (At least for me :))
> {
> - ctx->flags |= SAVE_RA;
> -}
> + const struct bpf_prog *prog = ctx->prog;
> + const bool is_main_prog = !bpf_is_subprog(prog);
>
> -static void mark_tail_call(struct jit_ctx *ctx)
> -{
> - ctx->flags |= SAVE_TCC;
> -}
> + if (is_main_prog) {
> + emit_insn(ctx, addid, LOONGARCH_GPR_T3, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> + *store_offset -= sizeof(long);
>
> -static bool seen_call(struct jit_ctx *ctx)
> -{
> - return (ctx->flags & SAVE_RA);
> -}
> + emit_tailcall_jmp(ctx, BPF_JGT, REG_TCC, LOONGARCH_GPR_T3, 4);
Why emit_tailcall_jmp() here ? Shouldn't this be emit_cond_jmp() ?
>
> -static bool seen_tail_call(struct jit_ctx *ctx)
> -{
> - return (ctx->flags & SAVE_TCC);
> -}
> + /* If REG_TCC < MAX_TAIL_CALL_CNT, push REG_TCC into stack */
> + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
>
> -static u8 tail_call_reg(struct jit_ctx *ctx)
> -{
> - if (seen_call(ctx))
> - return TCC_SAVED;
> + /* Calculate the pointer to REG_TCC in the stack and assign it to REG_TCC */
> + emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> +
> + emit_uncond_jmp(ctx, 2);
> +
> + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
>
> - return REG_TCC;
> + *store_offset -= sizeof(long);
> + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> +
> + } else {
> + *store_offset -= sizeof(long);
> + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> +
> + *store_offset -= sizeof(long);
> + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> + }
> }
>
> /*
> @@ -80,6 +84,10 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
> * | $s4 |
> * +-------------------------+
> * | $s5 |
> + * +-------------------------+
> + * | reg_tcc |
> + * +-------------------------+
> + * | reg_tcc_ptr |
> * +-------------------------+ <--BPF_REG_FP
> * | prog->aux->stack_depth |
> * | (optional) |
> @@ -89,21 +97,24 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
> static void build_prologue(struct jit_ctx *ctx)
> {
> int stack_adjust = 0, store_offset, bpf_stack_adjust;
> + const struct bpf_prog *prog = ctx->prog;
> + const bool is_main_prog = !bpf_is_subprog(prog);
>
> bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
>
> - /* To store ra, fp, s0, s1, s2, s3, s4 and s5. */
> - stack_adjust += sizeof(long) * 8;
> + /* To store ra, fp, s0, s1, s2, s3, s4, s5, reg_tcc and reg_tcc_ptr */
> + stack_adjust += sizeof(long) * 10;
>
> stack_adjust = round_up(stack_adjust, 16);
> stack_adjust += bpf_stack_adjust;
>
> /*
> - * First instruction initializes the tail call count (TCC).
> - * On tail call we skip this instruction, and the TCC is
> + * First instruction initializes the tail call count (TCC) register
> + * to zero. On tail call we skip this instruction, and the TCC is
> * passed in REG_TCC from the caller.
> */
> - emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> + if (is_main_prog)
> + emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, 0);
>
> emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_adjust);
>
> @@ -131,20 +142,13 @@ static void build_prologue(struct jit_ctx *ctx)
> store_offset -= sizeof(long);
> emit_insn(ctx, std, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, store_offset);
>
> + prepare_bpf_tail_call_cnt(ctx, &store_offset);
> +
> emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_adjust);
>
> if (bpf_stack_adjust)
> emit_insn(ctx, addid, regmap[BPF_REG_FP], LOONGARCH_GPR_SP, bpf_stack_adjust);
>
> - /*
> - * Program contains calls and tail calls, so REG_TCC need
> - * to be saved across calls.
> - */
> - if (seen_tail_call(ctx) && seen_call(ctx))
> - move_reg(ctx, TCC_SAVED, REG_TCC);
> - else
> - emit_insn(ctx, nop);
> -
> ctx->stack_size = stack_adjust;
> }
>
> @@ -177,6 +181,17 @@ static void __build_epilogue(struct jit_ctx *ctx, bool is_tail_call)
> load_offset -= sizeof(long);
> emit_insn(ctx, ldd, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, load_offset);
>
> + /*
> + * When push into the stack, follow the order of tcc then tcc_ptr.
> + * When pop from the stack, first pop tcc_ptr followed by tcc
> + */
> + load_offset -= 2*sizeof(long);
> + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
> +
> + /* pop tcc_ptr to REG_TCC */
> + load_offset += sizeof(long);
> + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
> +
> emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_adjust);
>
> if (!is_tail_call) {
> @@ -211,7 +226,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
> static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> {
> int off;
> - u8 tcc = tail_call_reg(ctx);
> + int tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
> u8 a1 = LOONGARCH_GPR_A1;
> u8 a2 = LOONGARCH_GPR_A2;
> u8 t1 = LOONGARCH_GPR_T1;
> @@ -240,11 +255,15 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> goto toofar;
>
> /*
> - * if (--TCC < 0)
> - * goto out;
> + * if ((*tcc_ptr)++ >= MAX_TAIL_CALL_CNT)
> + * goto out;
> */
> - emit_insn(ctx, addid, REG_TCC, tcc, -1);
> - if (emit_tailcall_jmp(ctx, BPF_JSLT, REG_TCC, LOONGARCH_GPR_ZERO, jmp_offset) < 0)
> + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
> + emit_insn(ctx, ldd, t3, REG_TCC, 0);
> + emit_insn(ctx, addid, t3, t3, 1);
> + emit_insn(ctx, std, t3, REG_TCC, 0);
> + emit_insn(ctx, addid, t2, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> + if (emit_tailcall_jmp(ctx, BPF_JSGT, t3, t2, jmp_offset) < 0)
> goto toofar;
>
> /*
> @@ -465,6 +484,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> const s16 off = insn->off;
> const s32 imm = insn->imm;
> const bool is32 = BPF_CLASS(insn->code) == BPF_ALU || BPF_CLASS(insn->code) == BPF_JMP32;
> + int tcc_ptr_off;
>
> switch (code) {
> /* dst = src */
> @@ -891,12 +911,17 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
>
> /* function call */
> case BPF_JMP | BPF_CALL:
> - mark_call(ctx);
> ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
> &func_addr, &func_addr_fixed);
> if (ret < 0)
> return ret;
>
> + if (insn->src_reg == BPF_PSEUDO_CALL) {
> + tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
> + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
> + }
> +
> +
> move_addr(ctx, t1, func_addr);
> emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0);
>
> @@ -907,7 +932,6 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
>
> /* tail call */
> case BPF_JMP | BPF_TAIL_CALL:
> - mark_tail_call(ctx);
> if (emit_bpf_tail_call(ctx, i) < 0)
> return -EINVAL;
> break;
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* re：[PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function
2025-07-16 1:31 ` Hengqi Chen
@ 2025-07-22 9:34 ` jianghaoran
0 siblings, 0 replies; 7+ messages in thread
From: jianghaoran @ 2025-07-22 9:34 UTC (permalink / raw)
To: Hengqi Chen
Cc: loongarch, bpf, kernel, chenhuacai, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
在 2025-07-16星期三的 09:31 +0800，Hengqi Chen写道：
> Hi Haoran,
>
> On Tue, Jul 8, 2025 at 3:19 PM Haoran Jiang <
jianghaoran@kylinos.cn> > wrote:
> >
> > The extra pass of bpf_int_jit_compile() skips JIT context initialization
> > which essentially skips offset calculation leaving out_offset = -1,
> > the jmp_offset in emit_bpf_tail_call is calculated
> > by #define jmp_offset (out_offset - (cur_offset)) is a negative number,
> > which does not meet expectations.The final generated assembly as follow.
> >
>
> "does not meet expectations" ? Simply "is wrong" ?
>
> The subject line should be something like:
> Fix jump offset calculation in tailcall
>
> It's a fix, not optimization.
>
> Other than that, feel free to add:
> Reviewed-by: Hengqi Chen <
hengqi.chen@gmail.com> >
I will make the modification in the next version.
> > 54: bgeu $a2, $t1, -8 # 0x0000004c
> > 58: addi.d $a6, $s5, -1
> > 5c: bltz $a6, -16 # 0x0000004c
> > 60: alsl.d $t2, $a2, $a1, 0x3
> > 64: ld.d $t2, $t2, 264
> > 68: beq $t2, $zero, -28 # 0x0000004c
> >
> > Before apply this patch, the follow test case will reveal soft
> > lock issues.
> >
> > cd tools/testing/selftests/bpf/
> > ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1
> >
> > dmesg:
> > watchdog: BUG: soft lockup - CPU#2 stuck for 26s!
> > [test_progs:25056]
> >
> > Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
> > Signed-off-by: Haoran Jiang <
> > jianghaoran@kylinos.cn
> > >
> > ---
> > arch/loongarch/net/bpf_jit.c | 21 ++++++---------------
> > 1 file changed, 6 insertions(+), 15 deletions(-)
> >
> > diff --git a/arch/loongarch/net/bpf_jit.c
> > b/arch/loongarch/net/bpf_jit.c
> > index fa1500d4aa3e..5061bfc978f2 100644
> > --- a/arch/loongarch/net/bpf_jit.c
> > +++ b/arch/loongarch/net/bpf_jit.c
> > @@ -208,9 +208,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
> > return true;
> > }
> >
> > -/* initialized on the first pass of build_body() */
> > -static int out_offset = -1;
> > -static int emit_bpf_tail_call(struct jit_ctx *ctx)
> > +static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> > {
> > int off;
> > u8 tcc = tail_call_reg(ctx);
> > @@ -220,9 +218,10 @@ static int emit_bpf_tail_call(struct
> > jit_ctx *ctx)
> > u8 t2 = LOONGARCH_GPR_T2;
> > u8 t3 = LOONGARCH_GPR_T3;
> > const int idx0 = ctx->idx;
> > + int tc_ninsn = 0;
> >
> > #define cur_offset (ctx->idx - idx0)
> > -#define jmp_offset (out_offset - (cur_offset))
> > +#define jmp_offset (tc_ninsn - (cur_offset))
> >
> > /*
> > * a0: &ctx
> > @@ -232,6 +231,8 @@ static int emit_bpf_tail_call(struct
> > jit_ctx *ctx)
> > * if (index >= array->map.max_entries)
> > * goto out;
> > */
> > + tc_ninsn = insn ? ctx->offset[insn+1] - ctx-
> > >offset[insn] :
> > + ctx->offset[0];
> > off = offsetof(struct bpf_array, map.max_entries);
> > emit_insn(ctx, ldwu, t1, a1, off);
> > /* bgeu $a2, $t1, jmp_offset */
> > @@ -263,15 +264,6 @@ static int emit_bpf_tail_call(struct
> > jit_ctx *ctx)
> > emit_insn(ctx, ldd, t3, t2, off);
> > __build_epilogue(ctx, true);
> >
> > - /* out: */
> > - if (out_offset == -1)
> > - out_offset = cur_offset;
> > - if (cur_offset != out_offset) {
> > - pr_err_once("tail_call out_offset = %d,
> > expected %d!\n",
> > - cur_offset, out_offset);
> > - return -1;
> > - }
> > -
> > return 0;
> >
> > toofar:
> > @@ -916,7 +908,7 @@ static int build_insn(const struct bpf_insn
> > *insn, struct jit_ctx *ctx, bool ext
> > /* tail call */
> > case BPF_JMP | BPF_TAIL_CALL:
> > mark_tail_call(ctx);
> > - if (emit_bpf_tail_call(ctx) < 0)
> > + if (emit_bpf_tail_call(ctx, i) < 0)
> > return -EINVAL;
> > break;
> >
> > @@ -1342,7 +1334,6 @@ struct bpf_prog
> > *bpf_int_jit_compile(struct bpf_prog *prog)
> > if (tmp_blinded)
> > bpf_jit_prog_release_other(prog, prog ==
> > orig_prog ? tmp : orig_prog);
> >
> > - out_offset = -1;
> >
> > return prog;
> >
> > --
> > 2.43.0
> >
> >
^ permalink raw reply [flat|nested] 7+ messages in thread
* re：[PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy
2025-07-16 2:28 ` Hengqi Chen
@ 2025-07-22 9:56 ` jianghaoran
0 siblings, 0 replies; 7+ messages in thread
From: jianghaoran @ 2025-07-22 9:56 UTC (permalink / raw)
To: Hengqi Chen
Cc: loongarch, bpf, kernel, chenhuacai, yangtiezhu, jolsa, haoluo,
sdf, kpsingh, john.fastabend, yonghong.song, song, eddyz87,
martin.lau, andrii, daniel, ast
在 2025-07-16星期三的 10:28 +0800，Hengqi Chen写道：
> On Tue, Jul 8, 2025 at 3:19 PM Haoran Jiang <
> jianghaoran@kylinos.cn
> > wrote:
> > In specific use cases combining tailcalls and BPF-to-BPF calls，
> > MAX_TAIL_CALL_CNT won't work because of missing tail_call_cnt
> > back-propagation from callee to caller。This patch fixes this
> > tailcall issue caused by abusing the tailcall in bpf2bpf
> > feature
> > on LoongArch like the way of "bpf, x64: Fix tailcall
> > hierarchy".
> >
> > push tail_call_cnt_ptr and tail_call_cnt into the stack,
> > tail_call_cnt_ptr is passed between tailcall and bpf2bpf,
> > uses tail_call_cnt_ptr to increment tail_call_cnt.
> >
> > Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf
> > and tailcalls")
> > Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
> > Signed-off-by: Haoran Jiang <
> > jianghaoran@kylinos.cn
> > >
> > ---
> > arch/loongarch/net/bpf_jit.c | 112 +++++++++++++++++++++----
> > ----------
> > 1 file changed, 68 insertions(+), 44 deletions(-)
> >
> > diff --git a/arch/loongarch/net/bpf_jit.c
> > b/arch/loongarch/net/bpf_jit.c
> > index 5061bfc978f2..45f804b7c556 100644
> > --- a/arch/loongarch/net/bpf_jit.c
> > +++ b/arch/loongarch/net/bpf_jit.c
> > @@ -7,10 +7,9 @@
> > #include "bpf_jit.h"
> >
> > #define REG_TCC LOONGARCH_GPR_A6
> > -#define TCC_SAVED LOONGARCH_GPR_S5
> >
> > -#define SAVE_RA BIT(0)
> > -#define SAVE_TCC BIT(1)
> > +#define BPF_TAIL_CALL_CNT_PTR_STACK_OFF(stack)
> > (round_up(stack, 16) - 80)
> > +
> >
> > static const int regmap[] = {
> > /* return value from in-kernel function, and exit value
> > for eBPF program */
> > @@ -32,32 +31,37 @@ static const int regmap[] = {
> > [BPF_REG_AX] = LOONGARCH_GPR_T0,
> > };
> >
> > -static void mark_call(struct jit_ctx *ctx)
> > +static void prepare_bpf_tail_call_cnt(struct jit_ctx *ctx, int
> > *store_offset)
>
> Consider adding more comments(e.g. pseudocode) for
> prepare_bpf_tail_call_cnt().
> Assembly is hard to read. (At least for me :))
>
I will improve the comment information in the next version.\x01\b
>
> > {
> > - ctx->flags |= SAVE_RA;
> > -}
> > + const struct bpf_prog *prog = ctx->prog;
> > + const bool is_main_prog = !bpf_is_subprog(prog);
> >
> > -static void mark_tail_call(struct jit_ctx *ctx)
> > -{
> > - ctx->flags |= SAVE_TCC;
> > -}
> > + if (is_main_prog) {
> > + emit_insn(ctx, addid, LOONGARCH_GPR_T3, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> > + *store_offset -= sizeof(long);
> >
> > -static bool seen_call(struct jit_ctx *ctx)
> > -{
> > - return (ctx->flags & SAVE_RA);
> > -}
> > + emit_tailcall_jmp(ctx, BPF_JGT, REG_TCC, LOONGARCH_GPR_T3, 4);
>
> Why emit_tailcall_jmp() here ? Shouldn't this be emit_cond_jmp() ?
It's more appropriate to use emit_cond_jmp here.
>
> >
> > -static bool seen_tail_call(struct jit_ctx *ctx)
> > -{
> > - return (ctx->flags & SAVE_TCC);
> > -}
> > + /* If REG_TCC < MAX_TAIL_CALL_CNT, push REG_TCC into stack */
> > + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> >
> > -static u8 tail_call_reg(struct jit_ctx *ctx)
> > -{
> > - if (seen_call(ctx))
> > - return TCC_SAVED;
> > + /* Calculate the pointer to REG_TCC in the stack and assign it to REG_TCC */
> > + emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> > +
> > + emit_uncond_jmp(ctx, 2);
> > +
> > + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> >
> > - return REG_TCC;
> > + *store_offset -= sizeof(long);
> > + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> > +
> > + } else {
> > + *store_offset -= sizeof(long);
> > + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> > +
> > + *store_offset -= sizeof(long);
> > + emit_insn(ctx, std, REG_TCC, LOONGARCH_GPR_SP, *store_offset);
> > + }
> > }
> >
> > /*
> > @@ -80,6 +84,10 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
> > * | $s4 |
> > * +-------------------------+
> > * | $s5 |
> > + * +-------------------------+
> > + * | reg_tcc |
> > + * +-------------------------+
> > + * | reg_tcc_ptr |
> > * +-------------------------+ <--BPF_REG_FP
> > * | prog->aux->stack_depth |
> > * | (optional) |
> > @@ -89,21 +97,24 @@ static u8 tail_call_reg(struct jit_ctx *ctx)
> > static void build_prologue(struct jit_ctx *ctx)
> > {
> > int stack_adjust = 0, store_offset, bpf_stack_adjust;
> > + const struct bpf_prog *prog = ctx->prog;
> > + const bool is_main_prog = !bpf_is_subprog(prog);
> >
> > bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
> >
> > - /* To store ra, fp, s0, s1, s2, s3, s4 and s5. */
> > - stack_adjust += sizeof(long) * 8;
> > + /* To store ra, fp, s0, s1, s2, s3, s4, s5, reg_tcc and reg_tcc_ptr */
> > + stack_adjust += sizeof(long) * 10;
> >
> > stack_adjust = round_up(stack_adjust, 16);
> > stack_adjust += bpf_stack_adjust;
> >
> > /*
> > - * First instruction initializes the tail call count (TCC).
> > - * On tail call we skip this instruction, and the TCC is
> > + * First instruction initializes the tail call count (TCC) register
> > + * to zero. On tail call we skip this instruction, and the TCC is
> > * passed in REG_TCC from the caller.
> > */
> > - emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> > + if (is_main_prog)
> > + emit_insn(ctx, addid, REG_TCC, LOONGARCH_GPR_ZERO, 0);
> >
> > emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_adjust);
> >
> > @@ -131,20 +142,13 @@ static void build_prologue(struct jit_ctx *ctx)
> > store_offset -= sizeof(long);
> > emit_insn(ctx, std, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, store_offset);
> >
> > + prepare_bpf_tail_call_cnt(ctx, &store_offset);
> > +
> > emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_adjust);
> >
> > if (bpf_stack_adjust)
> > emit_insn(ctx, addid, regmap[BPF_REG_FP], LOONGARCH_GPR_SP, bpf_stack_adjust);
> >
> > - /*
> > - * Program contains calls and tail calls, so REG_TCC need
> > - * to be saved across calls.
> > - */
> > - if (seen_tail_call(ctx) && seen_call(ctx))
> > - move_reg(ctx, TCC_SAVED, REG_TCC);
> > - else
> > - emit_insn(ctx, nop);
> > -
> > ctx->stack_size = stack_adjust;
> > }
> >
> > @@ -177,6 +181,17 @@ static void __build_epilogue(struct jit_ctx *ctx, bool is_tail_call)
> > load_offset -= sizeof(long);
> > emit_insn(ctx, ldd, LOONGARCH_GPR_S5, LOONGARCH_GPR_SP, load_offset);
> >
> > + /*
> > + * When push into the stack, follow the order of tcc then tcc_ptr.
> > + * When pop from the stack, first pop tcc_ptr followed by tcc
> > + */
> > + load_offset -= 2*sizeof(long);
> > + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
> > +
> > + /* pop tcc_ptr to REG_TCC */
> > + load_offset += sizeof(long);
> > + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset);
> > +
> > emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_adjust);
> >
> > if (!is_tail_call) {
> > @@ -211,7 +226,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
> > static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> > {
> > int off;
> > - u8 tcc = tail_call_reg(ctx);
> > + int tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
> > u8 a1 = LOONGARCH_GPR_A1;
> > u8 a2 = LOONGARCH_GPR_A2;
> > u8 t1 = LOONGARCH_GPR_T1;
> > @@ -240,11 +255,15 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
> > goto toofar;
> >
> > /*
> > - * if (--TCC < 0)
> > - * goto out;
> > + * if ((*tcc_ptr)++ >= MAX_TAIL_CALL_CNT)
> > + * goto out;
> > */
> > - emit_insn(ctx, addid, REG_TCC, tcc, -1);
> > - if (emit_tailcall_jmp(ctx, BPF_JSLT, REG_TCC, LOONGARCH_GPR_ZERO, jmp_offset) < 0)
> > + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
> > + emit_insn(ctx, ldd, t3, REG_TCC, 0);
> > + emit_insn(ctx, addid, t3, t3, 1);
> > + emit_insn(ctx, std, t3, REG_TCC, 0);
> > + emit_insn(ctx, addid, t2, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT);
> > + if (emit_tailcall_jmp(ctx, BPF_JSGT, t3, t2, jmp_offset) < 0)
> > goto toofar;
> >
> > /*
> > @@ -465,6 +484,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> > const s16 off = insn->off;
> > const s32 imm = insn->imm;
> > const bool is32 = BPF_CLASS(insn->code) == BPF_ALU || BPF_CLASS(insn->code) == BPF_JMP32;
> > + int tcc_ptr_off;
> >
> > switch (code) {
> > /* dst = src */
> > @@ -891,12 +911,17 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> >
> > /* function call */
> > case BPF_JMP | BPF_CALL:
> > - mark_call(ctx);
> > ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
> > &func_addr, &func_addr_fixed);
> > if (ret < 0)
> > return ret;
> >
> > + if (insn->src_reg == BPF_PSEUDO_CALL) {
> > + tcc_ptr_off = BPF_TAIL_CALL_CNT_PTR_STACK_OFF(ctx->stack_size);
> > + emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off);
> > + }
> > +
> > +
> > move_addr(ctx, t1, func_addr);
> > emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0);
> >
> > @@ -907,7 +932,6 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
> >
> > /* tail call */
> > case BPF_JMP | BPF_TAIL_CALL:
> > - mark_tail_call(ctx);
> > if (emit_bpf_tail_call(ctx, i) < 0)
> > return -EINVAL;
> > break;
> > --
> > 2.43.0
> >
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2025-07-22 9:56 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-07-08 7:18 [PATCH v2 0/2] Fix two tailcall-related issues Haoran Jiang
2025-07-08 7:18 ` [PATCH v2 1/2] LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function Haoran Jiang
2025-07-16 1:31 ` Hengqi Chen
2025-07-22 9:34 ` re：[PATCH " jianghaoran
2025-07-08 7:18 ` [PATCH v2 2/2] LoongArch: BPF: Fix tailcall hierarchy Haoran Jiang
2025-07-16 2:28 ` Hengqi Chen
2025-07-22 9:56 ` re：[PATCH " jianghaoran
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).