From 7833deb95e05bec146414b3a2feb24f025ca27c0 Mon Sep 17 00:00:00 2001 From: Hari Bathini Date: Tue, 22 Apr 2025 13:56:09 +0530 Subject: powerpc/bpf: fix JIT code size calculation of bpf trampoline commit 59ba025948be2a92e8bc9ae1cbdaf197660bd508 upstream. arch_bpf_trampoline_size() provides JIT size of the BPF trampoline before the buffer for JIT'ing it is allocated. The total number of instructions emitted for BPF trampoline JIT code depends on where the final image is located. So, the size arrived at with the dummy pass in arch_bpf_trampoline_size() can vary from the actual size needed in arch_prepare_bpf_trampoline(). When the instructions accounted in arch_bpf_trampoline_size() is less than the number of instructions emitted during the actual JIT compile of the trampoline, the below warning is produced: WARNING: CPU: 8 PID: 204190 at arch/powerpc/net/bpf_jit_comp.c:981 __arch_prepare_bpf_trampoline.isra.0+0xd2c/0xdcc which is: /* Make sure the trampoline generation logic doesn't overflow */ if (image && WARN_ON_ONCE(&image[ctx->idx] > (u32 *)rw_image_end - BPF_INSN_SAFETY)) { So, during the dummy pass, instead of providing some arbitrary image location, account for maximum possible instructions if and when there is a dependency with image location for JIT'ing. Fixes: d243b62b7bd3 ("powerpc64/bpf: Add support for bpf trampolines") Reported-by: Venkat Rao Bagalkote Closes: https://lore.kernel.org/all/6168bfc8-659f-4b5a-a6fb-90a916dde3b3@linux.ibm.com/ Cc: stable@vger.kernel.org # v6.13+ Acked-by: Naveen N Rao (AMD) Tested-by: Venkat Rao Bagalkote Signed-off-by: Hari Bathini Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20250422082609.949301-1-hbathini@linux.ibm.com Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/net/bpf_jit_comp.c | 33 ++++++++++----------------------- 1 file changed, 10 insertions(+), 23 deletions(-) (limited to 'arch/powerpc/net/bpf_jit_comp.c') diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index 2991bb171a9b..c0684733e9d6 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -504,10 +504,11 @@ static int invoke_bpf_prog(u32 *image, u32 *ro_image, struct codegen_context *ct EMIT(PPC_RAW_ADDI(_R3, _R1, regs_off)); if (!p->jited) PPC_LI_ADDR(_R4, (unsigned long)p->insnsi); - if (!create_branch(&branch_insn, (u32 *)&ro_image[ctx->idx], (unsigned long)p->bpf_func, - BRANCH_SET_LINK)) { - if (image) - image[ctx->idx] = ppc_inst_val(branch_insn); + /* Account for max possible instructions during dummy pass for size calculation */ + if (image && !create_branch(&branch_insn, (u32 *)&ro_image[ctx->idx], + (unsigned long)p->bpf_func, + BRANCH_SET_LINK)) { + image[ctx->idx] = ppc_inst_val(branch_insn); ctx->idx++; } else { EMIT(PPC_RAW_LL(_R12, _R25, offsetof(struct bpf_prog, bpf_func))); @@ -889,7 +890,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im bpf_trampoline_restore_tail_call_cnt(image, ctx, func_frame_offset, r4_off); /* Reserve space to patch branch instruction to skip fexit progs */ - im->ip_after_call = &((u32 *)ro_image)[ctx->idx]; + if (ro_image) /* image is NULL for dummy pass */ + im->ip_after_call = &((u32 *)ro_image)[ctx->idx]; EMIT(PPC_RAW_NOP()); } @@ -912,7 +914,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im } if (flags & BPF_TRAMP_F_CALL_ORIG) { - im->ip_epilogue = &((u32 *)ro_image)[ctx->idx]; + if (ro_image) /* image is NULL for dummy pass */ + im->ip_epilogue = &((u32 *)ro_image)[ctx->idx]; PPC_LI_ADDR(_R3, im); ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx, (unsigned long)__bpf_tramp_exit); @@ -973,25 +976,9 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags, struct bpf_tramp_links *tlinks, void *func_addr) { struct bpf_tramp_image im; - void *image; int ret; - /* - * Allocate a temporary buffer for __arch_prepare_bpf_trampoline(). - * This will NOT cause fragmentation in direct map, as we do not - * call set_memory_*() on this buffer. - * - * We cannot use kvmalloc here, because we need image to be in - * module memory range. - */ - image = bpf_jit_alloc_exec(PAGE_SIZE); - if (!image) - return -ENOMEM; - - ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image, - m, flags, tlinks, func_addr); - bpf_jit_free_exec(image); - + ret = __arch_prepare_bpf_trampoline(&im, NULL, NULL, NULL, m, flags, tlinks, func_addr); return ret; } -- cgit v1.2.3