tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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powerpc64/bpf: do not increment tailcall count when prog is NULL

Do not increment tailcall count, if tailcall did not succeed due to
missing BPF program.

Fixes: ce0761419fae ("powerpc/bpf: Implement support for tail calls")
Cc: stable@vger.kernel.org
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260303181031.390073-2-hbathini@linux.ibm.com

authored by

Hari Bathini and committed by
Madhavan Srinivasan 521bd39d db54c287

+21 -18
+21 -18
arch/powerpc/net/bpf_jit_comp64.c
··· 522 522 523 523 /* 524 524 * tail_call_info++; <- Actual value of tcc here 525 + * Writeback this updated value only if tailcall succeeds. 525 526 */ 526 527 EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), 1)); 528 + 529 + /* prog = array->ptrs[index]; */ 530 + EMIT(PPC_RAW_MULI(bpf_to_ppc(TMP_REG_2), b2p_index, 8)); 531 + EMIT(PPC_RAW_ADD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2), b2p_bpf_array)); 532 + EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2), 533 + offsetof(struct bpf_array, ptrs))); 534 + 535 + /* 536 + * if (prog == NULL) 537 + * goto out; 538 + */ 539 + EMIT(PPC_RAW_CMPLDI(bpf_to_ppc(TMP_REG_2), 0)); 540 + PPC_BCC_SHORT(COND_EQ, out); 541 + 542 + /* goto *(prog->bpf_func + prologue_size); */ 543 + EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2), 544 + offsetof(struct bpf_prog, bpf_func))); 545 + EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2), 546 + FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size)); 547 + EMIT(PPC_RAW_MTCTR(bpf_to_ppc(TMP_REG_2))); 527 548 528 549 /* 529 550 * Before writing updated tail_call_info, distinguish if current frame ··· 559 538 EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_2), _R1, bpf_jit_stack_tailcallinfo_offset(ctx))); 560 539 /* Writeback updated value to tail_call_info */ 561 540 EMIT(PPC_RAW_STD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_2), 0)); 562 - 563 - /* prog = array->ptrs[index]; */ 564 - EMIT(PPC_RAW_MULI(bpf_to_ppc(TMP_REG_1), b2p_index, 8)); 565 - EMIT(PPC_RAW_ADD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), b2p_bpf_array)); 566 - EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), offsetof(struct bpf_array, ptrs))); 567 - 568 - /* 569 - * if (prog == NULL) 570 - * goto out; 571 - */ 572 - EMIT(PPC_RAW_CMPLDI(bpf_to_ppc(TMP_REG_1), 0)); 573 - PPC_BCC_SHORT(COND_EQ, out); 574 - 575 - /* goto *(prog->bpf_func + prologue_size); */ 576 - EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), offsetof(struct bpf_prog, bpf_func))); 577 - EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), 578 - FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size)); 579 - EMIT(PPC_RAW_MTCTR(bpf_to_ppc(TMP_REG_1))); 580 541 581 542 /* tear down stack, restore NVRs, ... */ 582 543 bpf_jit_emit_common_epilogue(image, ctx);