[PATCH] powerpc/bpf: populate extable entries only during the last pass

[Christophe Leroy]

Le 06/04/2023 à 09:35, Hari Bathini a écrit :
> Since commit 85e031154c7c ("powerpc/bpf: Perform complete extra passes
> to update addresses"), two additional passes are performed to avoid
> space and CPU time wastage on powerpc. But these extra passes led to
> WARN_ON_ONCE() hits in bpf_add_extable_entry(). Fix it by not adding
> extable entries during the extra pass.

Are you sure this change is correct ?
During the extra pass the code can get shrinked or expanded (within the 
limits of the size of the preliminary pass). Shouldn't extable entries 
be populated during the last pass ?

Christophe

> 
> Fixes: 85e031154c7c ("powerpc/bpf: Perform complete extra passes to update addresses")
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>   arch/powerpc/net/bpf_jit_comp32.c | 2 +-
>   arch/powerpc/net/bpf_jit_comp64.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
> index 7f91ea064c08..e788b1fbeee6 100644
> --- a/arch/powerpc/net/bpf_jit_comp32.c
> +++ b/arch/powerpc/net/bpf_jit_comp32.c
> @@ -977,7 +977,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   			if (size != BPF_DW && !fp->aux->verifier_zext)
>   				EMIT(PPC_RAW_LI(dst_reg_h, 0));
>   
> -			if (BPF_MODE(code) == BPF_PROBE_MEM) {
> +			if (BPF_MODE(code) == BPF_PROBE_MEM && !extra_pass) {
>   				int insn_idx = ctx->idx - 1;
>   				int jmp_off = 4;
>   
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index 8dd3cabaa83a..1cc2777ec846 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -921,7 +921,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   			if (size != BPF_DW && insn_is_zext(&insn[i + 1]))
>   				addrs[++i] = ctx->idx * 4;
>   
> -			if (BPF_MODE(code) == BPF_PROBE_MEM) {
> +			if (BPF_MODE(code) == BPF_PROBE_MEM && !extra_pass) {
>   				ret = bpf_add_extable_entry(fp, image, pass, ctx, ctx->idx - 1,
>   							    4, dst_reg);
>   				if (ret)