6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tiezhu Yang commit fd3cb1bfeb9d98618bd709bfee9c1133e9f189e6 upstream. The legacy epilogue implementation pops the tail call counter (TCC) context via a redundant double-load pattern. It first decrements the load_offset by 2 slots to fetch 'tcc_ptr', and then immediately bumps it back up by 1 slot to load the original 'tcc' value into REG_TCC, unnecessarily overwriting the register. Optimize this sequence by adjusting the load_offset by only 1 slot. This aligns the offset directly with the higher stack slot containing the entry TCC counter (or caller state), allowing us to restore the REG_TCC register safely with a single load. This removes one redundant instruction from the epilogue hot path, improves code readability, and ensures the correct TCC register context is handed back cleanly upon normal return. Cc: stable@vger.kernel.org Fixes: c0fcc955ff82 ("LoongArch: BPF: Fix the tailcall hierarchy") Fixes: ef54c517a937 ("LoongArch: BPF: Implement PROBE_MEM32 pseudo instructions") Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen Signed-off-by: Greg Kroah-Hartman --- arch/loongarch/net/bpf_jit.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -228,14 +228,8 @@ static void __build_epilogue(struct jit_ 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 then followed by tcc. - */ - load_offset -= 2 * sizeof(long); - emit_insn(ctx, ldd, REG_TCC, LOONGARCH_GPR_SP, load_offset); - - load_offset += sizeof(long); + /* Only restore the TCC state into REG_TCC from the higher slot */ + 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);