Re: [PATCH v2 4/4] powerpc/bpf: use bpf_jit_binary_pack_[alloc|finalize|free]

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Le 09/03/2023 à 19:02, Hari Bathini a écrit :
> Use bpf_jit_binary_pack_alloc in powerpc jit. The jit engine first
> writes the program to the rw buffer. When the jit is done, the program
> is copied to the final location with bpf_jit_binary_pack_finalize.
> With multiple jit_subprogs, bpf_jit_free is called on some subprograms
> that haven't got bpf_jit_binary_pack_finalize() yet. Implement custom
> bpf_jit_free() like in commit 1d5f82d9dd47 ("bpf, x86: fix freeing of
> not-finalized bpf_prog_pack") to call bpf_jit_binary_pack_finalize(),
> if necessary. While here, correct the misnomer powerpc64_jit_data to
> powerpc_jit_data as it is meant for both ppc32 and ppc64.

root@vgoip:~# echo 1 > /proc/sys/net/core/bpf_jit_enable
root@vgoip:~# insmod test_bpf.ko
[  570.270983] kernel tried to execute exec-protected page (bd42c198) - 
exploit attempt? (uid: 0)
[  570.279414] BUG: Unable to handle kernel instruction fetch
[  570.284822] Faulting instruction address: 0xbd42c198
[  570.289734] Oops: Kernel access of bad area, sig: 11 [#1]
[  570.295062] BE PAGE_SIZE=16K PREEMPT CMPC885
[  570.302811] Modules linked in: test_bpf(+) test_module
[  570.307891] CPU: 0 PID: 559 Comm: insmod Not tainted 
6.3.0-rc1-s3k-dev-g4ae0418b3500 #258
[  570.315975] Hardware name: MIAE 8xx 0x500000 CMPC885
[  570.320882] NIP:  bd42c198 LR: be8180ec CTR: be818010
[  570.325873] REGS: cae2bc40 TRAP: 0400   Not tainted 
(6.3.0-rc1-s3k-dev-g4ae0418b3500)
[  570.333704] MSR:  40009032 <EE,ME,IR,DR,RI>  CR: 88008222  XER: 00000000
[  570.340503]
[  570.340503] GPR00: be806eac cae2bd00 c2977340 00000000 c2c40900 
00000000 c1a18a80 00000000
[  570.340503] GPR08: 00000002 00000001 00000000 00000000 ffffffff 
100d815e ca6a0000 00000001
[  570.340503] GPR16: 1234aaaa ca242250 c1180000 00000001 1234aaab 
c9050030 00000000 00000000
[  570.340503] GPR24: c2c40900 00000000 ffffffff 00000000 c1a18a80 
00000000 00000002 ca24225c
[  570.376819] NIP [bd42c198] 0xbd42c198
[  570.380436] LR [be8180ec] 0xbe8180ec
[  570.383965] Call Trace:
[  570.386373] [cae2bd00] [0000000b] 0xb (unreliable)
[  570.391107] [cae2bd50] [be806eac] __run_one+0x58/0x224 [test_bpf]
[  570.397390] [cae2bd90] [be80ca94] test_bpf_init+0x8d8/0x1010 [test_bpf]
[  570.404189] [cae2be20] [c00049f0] do_one_initcall+0x38/0x1e4
[  570.409782] [cae2be80] [c0090aa8] do_init_module+0x50/0x234
[  570.415291] [cae2bea0] [c0092e08] sys_finit_module+0xb4/0xf8
[  570.420884] [cae2bf20] [c000e344] system_call_exception+0x94/0x150
[  570.426995] [cae2bf30] [c00120a8] ret_from_syscall+0x0/0x28
[  570.432502] --- interrupt: c00 at 0xfd5fca0
[  570.436632] NIP:  0fd5fca0 LR: 10014568 CTR: 10013294
[  570.441625] REGS: cae2bf40 TRAP: 0c00   Not tainted 
(6.3.0-rc1-s3k-dev-g4ae0418b3500)
[  570.449455] MSR:  0000d032 <EE,PR,ME,IR,DR,RI>  CR: 44002224  XER: 
00000000
[  570.456513]
[  570.456513] GPR00: 00000161 7f868d30 77ed34d0 00000003 100bc4ef 
00000000 0fd51868 0000d032
[  570.456513] GPR08: 000007b1 10013294 00000000 00000002 52454753 
100d815e 100a44b8 00000000
[  570.456513] GPR16: 100d167c 100b0000 1198426c 119854cd 100d0000 
100d0000 00000000 100a4498
[  570.456513] GPR24: ffffffa2 ffffffff 11984244 00000003 1198426c 
100bc4ef 11984288 1198426c
[  570.492828] NIP [0fd5fca0] 0xfd5fca0
[  570.496358] LR [10014568] 0x10014568
[  570.499887] --- interrupt: c00
[  570.502902] Code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
XXXXXXXX XXXXXXXX XXXXXXXX
[  570.517973] ---[ end trace 0000000000000000 ]---
[  570.522523]
[  570.523986] note: insmod[559] exited with irqs disabled
Segmentation fault

Christophe

> 
> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> ---
>   arch/powerpc/net/bpf_jit.h        |   7 +-
>   arch/powerpc/net/bpf_jit_comp.c   | 104 +++++++++++++++++++++---------
>   arch/powerpc/net/bpf_jit_comp32.c |   4 +-
>   arch/powerpc/net/bpf_jit_comp64.c |   6 +-
>   4 files changed, 83 insertions(+), 38 deletions(-)
> 
> diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
> index d767e39d5645..a8b7480c4d43 100644
> --- a/arch/powerpc/net/bpf_jit.h
> +++ b/arch/powerpc/net/bpf_jit.h
> @@ -168,15 +168,16 @@ 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, struct codegen_context *ctx, u64 func);
> -int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
> +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_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);
>   
> -int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct codegen_context *ctx,
> -			  int insn_idx, int jmp_off, int dst_reg);
> +int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass,
> +			  struct codegen_context *ctx, int insn_idx,
> +			  int jmp_off, int dst_reg);
>   
>   #endif
>   
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index d1794d9f0154..ece75c829499 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -42,10 +42,11 @@ int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg,
>   	return 0;
>   }
>   
> -struct powerpc64_jit_data {
> -	struct bpf_binary_header *header;
> +struct powerpc_jit_data {
> +	struct bpf_binary_header *hdr;
> +	struct bpf_binary_header *fhdr;
>   	u32 *addrs;
> -	u8 *image;
> +	u8 *fimage;
>   	u32 proglen;
>   	struct codegen_context ctx;
>   };
> @@ -62,15 +63,18 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   	u8 *image = NULL;
>   	u32 *code_base;
>   	u32 *addrs;
> -	struct powerpc64_jit_data *jit_data;
> +	struct powerpc_jit_data *jit_data;
>   	struct codegen_context cgctx;
>   	int pass;
>   	int flen;
> -	struct bpf_binary_header *bpf_hdr;
> +	struct bpf_binary_header *fhdr = NULL;
> +	struct bpf_binary_header *hdr = NULL;
>   	struct bpf_prog *org_fp = fp;
>   	struct bpf_prog *tmp_fp;
>   	bool bpf_blinded = false;
>   	bool extra_pass = false;
> +	u8 *fimage = NULL;
> +	u32 *fcode_base;
>   	u32 extable_len;
>   	u32 fixup_len;
>   
> @@ -100,9 +104,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   	addrs = jit_data->addrs;
>   	if (addrs) {
>   		cgctx = jit_data->ctx;
> -		image = jit_data->image;
> -		bpf_hdr = jit_data->header;
> +		fimage = jit_data->fimage;
> +		fhdr = jit_data->fhdr;
>   		proglen = jit_data->proglen;
> +		hdr = jit_data->hdr;
> +		image = (void *)hdr + ((void *)fimage - (void *)fhdr);
>   		extra_pass = true;
>   		goto skip_init_ctx;
>   	}
> @@ -120,7 +126,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   	cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
>   
>   	/* Scouting faux-generate pass 0 */
> -	if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0, false)) {
> +	if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
>   		/* We hit something illegal or unsupported. */
>   		fp = org_fp;
>   		goto out_addrs;
> @@ -135,7 +141,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   	 */
>   	if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) {
>   		cgctx.idx = 0;
> -		if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0, false)) {
> +		if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
>   			fp = org_fp;
>   			goto out_addrs;
>   		}
> @@ -157,17 +163,19 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   	proglen = cgctx.idx * 4;
>   	alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
>   
> -	bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns);
> -	if (!bpf_hdr) {
> +	fhdr = bpf_jit_binary_pack_alloc(alloclen, &fimage, 4, &hdr, &image,
> +					      bpf_jit_fill_ill_insns);
> +	if (!fhdr) {
>   		fp = org_fp;
>   		goto out_addrs;
>   	}
>   
>   	if (extable_len)
> -		fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len;
> +		fp->aux->extable = (void *)fimage + FUNCTION_DESCR_SIZE + proglen + fixup_len;
>   
>   skip_init_ctx:
>   	code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
> +	fcode_base = (u32 *)(fimage + FUNCTION_DESCR_SIZE);
>   
>   	/* Code generation passes 1-2 */
>   	for (pass = 1; pass < 3; pass++) {
> @@ -175,8 +183,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   		cgctx.idx = 0;
>   		cgctx.alt_exit_addr = 0;
>   		bpf_jit_build_prologue(code_base, &cgctx);
> -		if (bpf_jit_build_body(fp, code_base, &cgctx, addrs, pass, extra_pass)) {
> -			bpf_jit_binary_free(bpf_hdr);
> +		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));
> +			bpf_jit_binary_pack_free(fhdr, hdr);
>   			fp = org_fp;
>   			goto out_addrs;
>   		}
> @@ -192,21 +201,23 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   		 * Note that we output the base address of the code_base
>   		 * rather than image, since opcodes are in code_base.
>   		 */
> -		bpf_jit_dump(flen, proglen, pass, code_base);
> +		bpf_jit_dump(flen, proglen, pass, fcode_base);
>   
>   #ifdef CONFIG_PPC64_ELF_ABI_V1
>   	/* Function descriptor nastiness: Address + TOC */
> -	((u64 *)image)[0] = (u64)code_base;
> +	((u64 *)image)[0] = (u64)fcode_base;
>   	((u64 *)image)[1] = local_paca->kernel_toc;
>   #endif
>   
> -	fp->bpf_func = (void *)image;
> +	fp->bpf_func = (void *)fimage;
>   	fp->jited = 1;
>   	fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
>   
> -	bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + bpf_hdr->size);
>   	if (!fp->is_func || extra_pass) {
> -		bpf_jit_binary_lock_ro(bpf_hdr);
> +		if (bpf_jit_binary_pack_finalize(fp, fhdr, hdr)) {
> +			fp = org_fp;
> +			goto out_addrs;
> +		}
>   		bpf_prog_fill_jited_linfo(fp, addrs);
>   out_addrs:
>   		kfree(addrs);
> @@ -216,8 +227,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>   		jit_data->addrs = addrs;
>   		jit_data->ctx = cgctx;
>   		jit_data->proglen = proglen;
> -		jit_data->image = image;
> -		jit_data->header = bpf_hdr;
> +		jit_data->fimage = fimage;
> +		jit_data->fhdr = fhdr;
> +		jit_data->hdr = hdr;
>   	}
>   
>   out:
> @@ -231,12 +243,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>    * The caller should check for (BPF_MODE(code) == BPF_PROBE_MEM) before calling
>    * this function, as this only applies to BPF_PROBE_MEM, for now.
>    */
> -int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct codegen_context *ctx,
> -			  int insn_idx, int jmp_off, int dst_reg)
> +int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass,
> +			  struct codegen_context *ctx, int insn_idx, int jmp_off,
> +			  int dst_reg)
>   {
>   	off_t offset;
>   	unsigned long pc;
> -	struct exception_table_entry *ex;
> +	struct exception_table_entry *ex, *ex_entry;
>   	u32 *fixup;
>   
>   	/* Populate extable entries only in the last pass */
> @@ -247,9 +260,16 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code
>   	    WARN_ON_ONCE(ctx->exentry_idx >= fp->aux->num_exentries))
>   		return -EINVAL;
>   
> +	/*
> +	 * Program is firt written to image before copying to the
> +	 * final location (fimage). Accordingly, update in the image first.
> +	 * As all offsets used are relative, copying as is to the
> +	 * final location should be alright.
> +	 */
>   	pc = (unsigned long)&image[insn_idx];
> +	ex = (void *)fp->aux->extable - (void *)fimage + (void *)image;
>   
> -	fixup = (void *)fp->aux->extable -
> +	fixup = (void *)ex -
>   		(fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
>   		(ctx->exentry_idx * BPF_FIXUP_LEN * 4);
>   
> @@ -260,17 +280,17 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code
>   	fixup[BPF_FIXUP_LEN - 1] =
>   		PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]);
>   
> -	ex = &fp->aux->extable[ctx->exentry_idx];
> +	ex_entry = &ex[ctx->exentry_idx];
>   
> -	offset = pc - (long)&ex->insn;
> +	offset = pc - (long)&ex_entry->insn;
>   	if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
>   		return -ERANGE;
> -	ex->insn = offset;
> +	ex_entry->insn = offset;
>   
> -	offset = (long)fixup - (long)&ex->fixup;
> +	offset = (long)fixup - (long)&ex_entry->fixup;
>   	if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
>   		return -ERANGE;
> -	ex->fixup = offset;
> +	ex_entry->fixup = offset;
>   
>   	ctx->exentry_idx++;
>   	return 0;
> @@ -308,3 +328,27 @@ int bpf_arch_text_invalidate(void *dst, size_t len)
>   
>   	return ret;
>   }
> +
> +void bpf_jit_free(struct bpf_prog *fp)
> +{
> +	if (fp->jited) {
> +		struct powerpc_jit_data *jit_data = fp->aux->jit_data;
> +		struct bpf_binary_header *hdr;
> +
> +		/*
> +		 * If we fail the final pass of JIT (from jit_subprogs),
> +		 * the program may not be finalized yet. Call finalize here
> +		 * before freeing it.
> +		 */
> +		if (jit_data) {
> +			bpf_jit_binary_pack_finalize(fp, jit_data->fhdr, jit_data->hdr);
> +			kvfree(jit_data->addrs);
> +			kfree(jit_data);
> +		}
> +		hdr = bpf_jit_binary_pack_hdr(fp);
> +		bpf_jit_binary_pack_free(hdr, NULL);
> +		WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
> +	}
> +
> +	bpf_prog_unlock_free(fp);
> +}
> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
> index 7f91ea064c08..fb2761b54d64 100644
> --- a/arch/powerpc/net/bpf_jit_comp32.c
> +++ b/arch/powerpc/net/bpf_jit_comp32.c
> @@ -278,7 +278,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
>   }
>   
>   /* Assemble the body code between the prologue & epilogue */
> -int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
> +int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct codegen_context *ctx,
>   		       u32 *addrs, int pass, bool extra_pass)
>   {
>   	const struct bpf_insn *insn = fp->insnsi;
> @@ -997,7 +997,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   					jmp_off += 4;
>   				}
>   
> -				ret = bpf_add_extable_entry(fp, image, pass, ctx, insn_idx,
> +				ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx, insn_idx,
>   							    jmp_off, dst_reg);
>   				if (ret)
>   					return ret;
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index 8dd3cabaa83a..37a8970a7065 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -343,7 +343,7 @@ asm (
>   );
>   
>   /* Assemble the body code between the prologue & epilogue */
> -int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
> +int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct codegen_context *ctx,
>   		       u32 *addrs, int pass, bool extra_pass)
>   {
>   	enum stf_barrier_type stf_barrier = stf_barrier_type_get();
> @@ -922,8 +922,8 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   				addrs[++i] = ctx->idx * 4;
>   
>   			if (BPF_MODE(code) == BPF_PROBE_MEM) {
> -				ret = bpf_add_extable_entry(fp, image, pass, ctx, ctx->idx - 1,
> -							    4, dst_reg);
> +				ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx,
> +							    ctx->idx - 1, 4, dst_reg);
>   				if (ret)
>   					return ret;
>   			}




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