diff options
| author | Tiezhu Yang <yangtiezhu@loongson.cn> | 2026-08-17 22:07:23 +0800 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2026-08-17 22:07:23 +0800 |
| commit | 37d545d12f21c4d50612ecaebd7ae1e5bf91b2d8 (patch) | |
| tree | b279888506bb2197cb6b6b6f44a3068dc333d24f /arch/loongarch/net | |
| parent | cd7e356b07a27e91394838cf3fb655862b519294 (diff) | |
LoongArch: BPF: Refactor jump offset calculation in tail call
The old macro-based jmp_offset calculation derives the jump distance
from a stale prior-pass code stride, which can lead to wrong branch
offsets and soft lockups under extra JIT passes.
Fix this by calculating the offset directly on the absolute target:
"ctx->offset[insn + 1] - ctx->idx".
To avoid a false 16-bit range check abort during size estimation, add
a "ctx->image == NULL" guard to inject a safe dummy offset.
Cc: stable@vger.kernel.org
Fixes: cd39d9e6b7e4 ("LoongArch: BPF: Fix jump offset calculation in tailcall")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch/loongarch/net')
| -rw-r--r-- | arch/loongarch/net/bpf_jit.c | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index fd5f8c4e5360..846d652b0d22 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -290,17 +290,13 @@ bool bpf_jit_supports_far_kfunc_call(void) static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn) { - int off, tc_ninsn = 0; + int off, jmp_offset; 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; u8 t2 = LOONGARCH_GPR_T2; u8 t3 = LOONGARCH_GPR_T3; - const int idx0 = ctx->idx; - -#define cur_offset (ctx->idx - idx0) -#define jmp_offset (tc_ninsn - (cur_offset)) /* * a0: &ctx @@ -310,12 +306,12 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn) * if (index >= array->map.max_entries) * goto out; */ - tc_ninsn = insn ? ctx->offset[insn+1] - ctx->offset[insn] : ctx->offset[0]; emit_zext_32(ctx, a2, true); off = offsetof(struct bpf_array, map.max_entries); emit_insn(ctx, ldwu, t1, a1, off); /* bgeu $a2, $t1, jmp_offset */ + jmp_offset = ctx->image ? (ctx->offset[insn + 1] - ctx->idx) : 0; if (emit_tailcall_jmp(ctx, BPF_JGE, a2, t1, jmp_offset) < 0) goto toofar; @@ -326,6 +322,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn) emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, tcc_ptr_off); emit_insn(ctx, ldd, t3, REG_TCC, 0); emit_insn(ctx, addid, t2, LOONGARCH_GPR_ZERO, MAX_TAIL_CALL_CNT); + jmp_offset = ctx->image ? (ctx->offset[insn + 1] - ctx->idx) : 0; if (emit_tailcall_jmp(ctx, BPF_JSGE, t3, t2, jmp_offset) < 0) goto toofar; @@ -340,6 +337,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn) off = offsetof(struct bpf_array, ptrs); emit_insn(ctx, ldd, t2, t2, off); /* beq $t2, $zero, jmp_offset */ + jmp_offset = ctx->image ? (ctx->offset[insn + 1] - ctx->idx) : 0; if (emit_tailcall_jmp(ctx, BPF_JEQ, t2, LOONGARCH_GPR_ZERO, jmp_offset) < 0) goto toofar; @@ -355,8 +353,6 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn) toofar: pr_info_once("tail_call: jump too far\n"); return -1; -#undef cur_offset -#undef jmp_offset } static void emit_store_stack_imm64(struct jit_ctx *ctx, int reg, int stack_off, u64 imm64) |