[PATCH v2 1/2] powerpc/bpf: ensure module addresses are supported
Christophe Leroy
christophe.leroy at csgroup.eu
Tue Feb 13 18:53:17 AEDT 2024
Le 01/02/2024 à 18:12, Hari Bathini a écrit :
> Currently, bpf jit code on powerpc assumes all the bpf functions and
> helpers to be kernel text. This is false for kfunc case, as function
> addresses are mostly module addresses in that case. Ensure module
> addresses are supported to enable kfunc support.
>
> Assume kernel text address for programs with no kfunc call to optimize
> instruction sequence in that case. Add a check to error out if this
> assumption ever changes in the future.
>
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>
> Changes in v2:
> * Using bpf_prog_has_kfunc_call() to decide whether to use optimized
> instruction sequence or not as suggested by Naveen.
>
>
> arch/powerpc/net/bpf_jit.h | 5 +-
> arch/powerpc/net/bpf_jit_comp.c | 4 +-
> arch/powerpc/net/bpf_jit_comp32.c | 8 ++-
> arch/powerpc/net/bpf_jit_comp64.c | 109 ++++++++++++++++++++++++------
> 4 files changed, 97 insertions(+), 29 deletions(-)
>
> diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
> index cdea5dccaefe..fc56ee0ee9c5 100644
> --- a/arch/powerpc/net/bpf_jit.h
> +++ b/arch/powerpc/net/bpf_jit.h
> @@ -160,10 +160,11 @@ static inline void bpf_clear_seen_register(struct codegen_context *ctx, int i)
> }
>
> void bpf_jit_init_reg_mapping(struct codegen_context *ctx);
> -int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func);
> +int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func,
> + bool has_kfunc_call);
> int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct codegen_context *ctx,
> u32 *addrs, int pass, bool extra_pass);
> -void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx);
> +void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx, bool has_kfunc_call);
> void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx);
> void bpf_jit_realloc_regs(struct codegen_context *ctx);
> int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr);
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 0f9a21783329..7b4103b4c929 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -163,7 +163,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> * update ctgtx.idx as it pretends to output instructions, then we can
> * calculate total size from idx.
> */
> - bpf_jit_build_prologue(NULL, &cgctx);
> + bpf_jit_build_prologue(NULL, &cgctx, bpf_prog_has_kfunc_call(fp));
> addrs[fp->len] = cgctx.idx * 4;
> bpf_jit_build_epilogue(NULL, &cgctx);
>
> @@ -192,7 +192,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> /* Now build the prologue, body code & epilogue for real. */
> cgctx.idx = 0;
> cgctx.alt_exit_addr = 0;
> - bpf_jit_build_prologue(code_base, &cgctx);
> + bpf_jit_build_prologue(code_base, &cgctx, bpf_prog_has_kfunc_call(fp));
> if (bpf_jit_build_body(fp, code_base, fcode_base, &cgctx, addrs, pass,
> extra_pass)) {
> bpf_arch_text_copy(&fhdr->size, &hdr->size, sizeof(hdr->size));
> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
> index 2f39c50ca729..447747e51a58 100644
> --- a/arch/powerpc/net/bpf_jit_comp32.c
> +++ b/arch/powerpc/net/bpf_jit_comp32.c
> @@ -123,7 +123,7 @@ void bpf_jit_realloc_regs(struct codegen_context *ctx)
> }
> }
>
> -void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
> +void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx, bool has_kfunc_call)
> {
> int i;
>
> @@ -201,7 +201,8 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
> }
>
> /* Relative offset needs to be calculated based on final image location */
> -int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
> +int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func,
> + bool has_kfunc_call)
> {
> s32 rel = (s32)func - (s32)(fimage + ctx->idx);
>
> @@ -1054,7 +1055,8 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> EMIT(PPC_RAW_STW(bpf_to_ppc(BPF_REG_5), _R1, 12));
> }
>
> - ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
> + ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr,
> + bpf_prog_has_kfunc_call(fp));
> if (ret)
> return ret;
>
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index 79f23974a320..385a5df1670c 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -122,12 +122,17 @@ void bpf_jit_realloc_regs(struct codegen_context *ctx)
> {
> }
>
> -void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
> +void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx, bool has_kfunc_call)
> {
> int i;
>
> #ifndef CONFIG_PPC_KERNEL_PCREL
> - if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
> + /*
> + * If the program doesn't have a kfunc call, all BPF helpers are part of kernel text
> + * and all BPF programs/functions utilize the kernel TOC. So, optimize the
> + * instruction sequence by using kernel toc in r2 for that case.
> + */
> + if (!has_kfunc_call && IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
> EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
> #endif
>
> @@ -202,12 +207,17 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
> EMIT(PPC_RAW_BLR());
> }
>
> -static int bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, u64 func)
> +static int bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, u64 func,
> + bool has_kfunc_call)
> {
> unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0;
> long reladdr;
>
> - if (WARN_ON_ONCE(!core_kernel_text(func_addr)))
> + /*
> + * If the program doesn't have a kfunc call, all BPF helpers are assumed to be part of
> + * kernel text. Don't proceed if that assumption ever changes in future.
> + */
> + if (!has_kfunc_call && WARN_ON_ONCE(!core_kernel_text(func_addr)))
> return -EINVAL;
>
> if (IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
> @@ -225,30 +235,55 @@ static int bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, u
> EMIT(PPC_RAW_BCTR());
>
> } else {
> - reladdr = func_addr - kernel_toc_addr();
> - if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> - pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func);
> - return -ERANGE;
> - }
> + if (has_kfunc_call) {
> +#ifdef PPC64_ELF_ABI_v1
I can't see a reason for a #ifdef here, why not use IS_ENABLED() like
other places ?
> + /* func points to the function descriptor */
> + PPC_LI64(b2p[TMP_REG_2], func);
> + /* Load actual entry point from function descriptor */
> + PPC_BPF_LL(b2p[TMP_REG_1], b2p[TMP_REG_2], 0);
> + /* ... and move it to CTR */
> + EMIT(PPC_RAW_MTCTR(b2p[TMP_REG_1]));
> + /*
> + * Load TOC from function descriptor at offset 8.
> + * We can clobber r2 since we get called through a
> + * function pointer (so caller will save/restore r2)
> + * and since we don't use a TOC ourself.
> + */
> + PPC_BPF_LL(2, b2p[TMP_REG_2], 8);
> +#else
> + /* We can clobber r12 */
> + PPC_LI64(12, func);
> + EMIT(PPC_RAW_MTCTR(12));
> +#endif
> + } else {
> + reladdr = func_addr - kernel_toc_addr();
> + if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> + pr_err("eBPF: address of %ps out of range of kernel_toc.\n",
> + (void *)func);
> + return -ERANGE;
> + }
>
> - EMIT(PPC_RAW_ADDIS(_R12, _R2, PPC_HA(reladdr)));
> - EMIT(PPC_RAW_ADDI(_R12, _R12, PPC_LO(reladdr)));
> - EMIT(PPC_RAW_MTCTR(_R12));
> + EMIT(PPC_RAW_ADDIS(_R12, _R2, PPC_HA(reladdr)));
> + EMIT(PPC_RAW_ADDI(_R12, _R12, PPC_LO(reladdr)));
> + EMIT(PPC_RAW_MTCTR(_R12));
> + }
> EMIT(PPC_RAW_BCTRL());
> }
>
> return 0;
> }
>
> -int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
> +int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func,
> + bool has_kfunc_call)
> {
> unsigned int i, ctx_idx = ctx->idx;
>
> - if (WARN_ON_ONCE(func && is_module_text_address(func)))
> + if (WARN_ON_ONCE(func && !has_kfunc_call && is_module_text_address(func)))
> return -EINVAL;
>
> /* skip past descriptor if elf v1 */
> - func += FUNCTION_DESCR_SIZE;
> + if (!has_kfunc_call)
> + func += FUNCTION_DESCR_SIZE;
>
> /* Load function address into r12 */
> PPC_LI64(_R12, func);
> @@ -267,13 +302,28 @@ int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *
> for (i = ctx->idx - ctx_idx; i < 5; i++)
> EMIT(PPC_RAW_NOP());
>
> +#ifdef PPC64_ELF_ABI_v1
I can't see a reason for a #ifdef here, why not use IS_ENABLED() like
other places ?
> + if (has_kfunc_call) {
> + /*
> + * Load TOC from function descriptor at offset 8.
> + * We can clobber r2 since we get called through a
> + * function pointer (so caller will save/restore r2)
> + * and since we don't use a TOC ourself.
> + */
> + PPC_BPF_LL(2, 12, 8);
> + /* Load actual entry point from function descriptor */
> + PPC_BPF_LL(12, 12, 0);
> + }
> +#endif
> +
> EMIT(PPC_RAW_MTCTR(_R12));
> EMIT(PPC_RAW_BCTRL());
>
> return 0;
> }
>
> -static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
> +static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out,
> + bool has_kfunc_call)
> {
> /*
> * By now, the eBPF program has already setup parameters in r3, r4 and r5
> @@ -285,7 +335,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
> int b2p_index = bpf_to_ppc(BPF_REG_3);
> int bpf_tailcall_prologue_size = 8;
>
> - if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
> + if (!has_kfunc_call && IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
> bpf_tailcall_prologue_size += 4; /* skip past the toc load */
>
> /*
> @@ -325,8 +375,20 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
>
> /* goto *(prog->bpf_func + prologue_size); */
> EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), offsetof(struct bpf_prog, bpf_func)));
> - EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1),
> - FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size));
> + if (has_kfunc_call) {
> +#ifdef PPC64_ELF_ABI_v1
I can't see a reason for a #ifdef here, why not use IS_ENABLED() like
other places ?
> + /* skip past the function descriptor */
> + EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1),
> + FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size));
> +#else
> + EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1),
> + bpf_tailcall_prologue_size));
> +#endif
> + } else {
> + EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1),
> + FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size));
> + }
> +
> EMIT(PPC_RAW_MTCTR(bpf_to_ppc(TMP_REG_1)));
>
> /* tear down stack, restore NVRs, ... */
> @@ -365,6 +427,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> u32 *addrs, int pass, bool extra_pass)
> {
> enum stf_barrier_type stf_barrier = stf_barrier_type_get();
> + bool has_kfunc_call = bpf_prog_has_kfunc_call(fp);
> const struct bpf_insn *insn = fp->insnsi;
> int flen = fp->len;
> int i, ret;
> @@ -993,9 +1056,11 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> return ret;
>
> if (func_addr_fixed)
> - ret = bpf_jit_emit_func_call_hlp(image, ctx, func_addr);
> + ret = bpf_jit_emit_func_call_hlp(image, ctx, func_addr,
> + has_kfunc_call);
Doesn't this fit on a single line ?
> else
> - ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
> + ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr,
> + has_kfunc_call);
Same. Nowadays lines up to 100 chars are the norm.
>
> if (ret)
> return ret;
> @@ -1204,7 +1269,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> */
> case BPF_JMP | BPF_TAIL_CALL:
> ctx->seen |= SEEN_TAILCALL;
> - ret = bpf_jit_emit_tail_call(image, ctx, addrs[i + 1]);
> + ret = bpf_jit_emit_tail_call(image, ctx, addrs[i + 1], has_kfunc_call);
> if (ret < 0)
> return ret;
> break;
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