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Commit 26eb042e authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf, arm64: add support for constant blinding 



This patch adds recently added constant blinding helpers into the
arm64 eBPF JIT. In the bpf_int_jit_compile() path, requirements are
to utilize bpf_jit_blind_constants()/bpf_jit_prog_release_other()
pair for rewriting the program into a blinded one, and to map the
BPF_REG_AX register to a CPU register. The mapping is on x9.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarZi Shen Lim <zlim.lnx@gmail.com>
Acked-by: default avatarYang Shi <yang.shi@linaro.org>
Tested-by: default avatarYang Shi <yang.shi@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 959a7579

arch/arm64/net/bpf_jit_comp.c

+40 −12
Original line number Diff line number Diff line
@@ -31,8 +31,8 @@ 


int bpf_jit_enable __read_mostly;



#define TMP_REG_1 (MAX_BPF_REG + 0)

#define TMP_REG_2 (MAX_BPF_REG + 1)

#define TMP_REG_1 (MAX_BPF_JIT_REG + 0)

#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)



/* Map BPF registers to A64 registers */

static const int bpf2a64[] = {
@@ -54,6 +54,8 @@ static const int bpf2a64[] = { 
	/* temporary register for internal BPF JIT */

	[TMP_REG_1] = A64_R(23),

	[TMP_REG_2] = A64_R(24),

	/* temporary register for blinding constants */

	[BPF_REG_AX] = A64_R(9),

};



struct jit_ctx {
@@ -764,26 +766,43 @@ void bpf_jit_compile(struct bpf_prog *prog) 


struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)

{

	struct bpf_prog *tmp, *orig_prog = prog;

	struct bpf_binary_header *header;

	bool tmp_blinded = false;

	struct jit_ctx ctx;

	int image_size;

	u8 *image_ptr;



	if (!bpf_jit_enable)

		return prog;

		return orig_prog;



	tmp = bpf_jit_blind_constants(prog);

	/* If blinding was requested and we failed during blinding,

	 * we must fall back to the interpreter.

	 */

	if (IS_ERR(tmp))

		return orig_prog;

	if (tmp != prog) {

		tmp_blinded = true;

		prog = tmp;

	}



	memset(&ctx, 0, sizeof(ctx));

	ctx.prog = prog;



	ctx.offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);

	if (ctx.offset == NULL)

		return prog;

	if (ctx.offset == NULL) {

		prog = orig_prog;

		goto out;

	}



	/* 1. Initial fake pass to compute ctx->idx. */



	/* Fake pass to fill in ctx->offset and ctx->tmp_used. */

	if (build_body(&ctx))

		goto out;

	if (build_body(&ctx)) {

		prog = orig_prog;

		goto out_off;

	}



	build_prologue(&ctx);
@@ -794,8 +813,10 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
	image_size = sizeof(u32) * ctx.idx;

	header = bpf_jit_binary_alloc(image_size, &image_ptr,

				      sizeof(u32), jit_fill_hole);

	if (header == NULL)

		goto out;

	if (header == NULL) {

		prog = orig_prog;

		goto out_off;

	}



	/* 2. Now, the actual pass. */
@@ -806,7 +827,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 


	if (build_body(&ctx)) {

		bpf_jit_binary_free(header);

		goto out;

		prog = orig_prog;

		goto out_off;

	}



	build_epilogue(&ctx);
@@ -814,7 +836,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
	/* 3. Extra pass to validate JITed code. */

	if (validate_code(&ctx)) {

		bpf_jit_binary_free(header);

		goto out;

		prog = orig_prog;

		goto out_off;

	}



	/* And we're done. */
@@ -826,8 +849,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
	set_memory_ro((unsigned long)header, header->pages);

	prog->bpf_func = (void *)ctx.image;

	prog->jited = 1;

out:



out_off:

	kfree(ctx.offset);

out:

	if (tmp_blinded)

		bpf_jit_prog_release_other(prog, prog == orig_prog ?

					   tmp : orig_prog);

	return prog;

}