summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/net/bpf_jit_comp.c
blob: 43e6341265148aade647f9a35da6a19d4ca48dd3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
// SPDX-License-Identifier: GPL-2.0-only
/*
 * eBPF JIT compiler
 *
 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
 *		  IBM Corporation
 *
 * Based on the powerpc classic BPF JIT compiler by Matt Evans
 */
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
#include <asm/asm-compat.h>
#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <asm/kprobes.h>
#include <linux/bpf.h>

#include "bpf_jit.h"

static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
{
	memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
}

/* Fix updated addresses (for subprog calls, ldimm64, et al) during extra pass */
static int bpf_jit_fixup_addresses(struct bpf_prog *fp, u32 *image,
				   struct codegen_context *ctx, u32 *addrs)
{
	const struct bpf_insn *insn = fp->insnsi;
	bool func_addr_fixed;
	u64 func_addr;
	u32 tmp_idx;
	int i, j, ret;

	for (i = 0; i < fp->len; i++) {
		/*
		 * During the extra pass, only the branch target addresses for
		 * the subprog calls need to be fixed. All other instructions
		 * can left untouched.
		 *
		 * The JITed image length does not change because we already
		 * ensure that the JITed instruction sequence for these calls
		 * are of fixed length by padding them with NOPs.
		 */
		if (insn[i].code == (BPF_JMP | BPF_CALL) &&
		    insn[i].src_reg == BPF_PSEUDO_CALL) {
			ret = bpf_jit_get_func_addr(fp, &insn[i], true,
						    &func_addr,
						    &func_addr_fixed);
			if (ret < 0)
				return ret;

			/*
			 * Save ctx->idx as this would currently point to the
			 * end of the JITed image and set it to the offset of
			 * the instruction sequence corresponding to the
			 * subprog call temporarily.
			 */
			tmp_idx = ctx->idx;
			ctx->idx = addrs[i] / 4;
			ret = bpf_jit_emit_func_call_rel(image, ctx, func_addr);
			if (ret)
				return ret;

			/*
			 * Restore ctx->idx here. This is safe as the length
			 * of the JITed sequence remains unchanged.
			 */
			ctx->idx = tmp_idx;
		} else if (insn[i].code == (BPF_LD | BPF_IMM | BPF_DW)) {
			tmp_idx = ctx->idx;
			ctx->idx = addrs[i] / 4;
#ifdef CONFIG_PPC32
			PPC_LI32(bpf_to_ppc(insn[i].dst_reg) - 1, (u32)insn[i + 1].imm);
			PPC_LI32(bpf_to_ppc(insn[i].dst_reg), (u32)insn[i].imm);
			for (j = ctx->idx - addrs[i] / 4; j < 4; j++)
				EMIT(PPC_RAW_NOP());
#else
			func_addr = ((u64)(u32)insn[i].imm) | (((u64)(u32)insn[i + 1].imm) << 32);
			PPC_LI64(bpf_to_ppc(insn[i].dst_reg), func_addr);
			/* overwrite rest with nops */
			for (j = ctx->idx - addrs[i] / 4; j < 5; j++)
				EMIT(PPC_RAW_NOP());
#endif
			ctx->idx = tmp_idx;
			i++;
		}
	}

	return 0;
}

int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
{
	if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
		PPC_JMP(exit_addr);
	} else if (ctx->alt_exit_addr) {
		if (WARN_ON(!is_offset_in_branch_range((long)ctx->alt_exit_addr - (ctx->idx * 4))))
			return -1;
		PPC_JMP(ctx->alt_exit_addr);
	} else {
		ctx->alt_exit_addr = ctx->idx * 4;
		bpf_jit_build_epilogue(image, ctx);
	}

	return 0;
}

struct powerpc64_jit_data {
	struct bpf_binary_header *header;
	u32 *addrs;
	u8 *image;
	u32 proglen;
	struct codegen_context ctx;
};

bool bpf_jit_needs_zext(void)
{
	return true;
}

struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
{
	u32 proglen;
	u32 alloclen;
	u8 *image = NULL;
	u32 *code_base;
	u32 *addrs;
	struct powerpc64_jit_data *jit_data;
	struct codegen_context cgctx;
	int pass;
	int flen;
	struct bpf_binary_header *bpf_hdr;
	struct bpf_prog *org_fp = fp;
	struct bpf_prog *tmp_fp;
	bool bpf_blinded = false;
	bool extra_pass = false;
	u32 extable_len;
	u32 fixup_len;

	if (!fp->jit_requested)
		return org_fp;

	tmp_fp = bpf_jit_blind_constants(org_fp);
	if (IS_ERR(tmp_fp))
		return org_fp;

	if (tmp_fp != org_fp) {
		bpf_blinded = true;
		fp = tmp_fp;
	}

	jit_data = fp->aux->jit_data;
	if (!jit_data) {
		jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
		if (!jit_data) {
			fp = org_fp;
			goto out;
		}
		fp->aux->jit_data = jit_data;
	}

	flen = fp->len;
	addrs = jit_data->addrs;
	if (addrs) {
		cgctx = jit_data->ctx;
		image = jit_data->image;
		bpf_hdr = jit_data->header;
		proglen = jit_data->proglen;
		extra_pass = true;
		goto skip_init_ctx;
	}

	addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
	if (addrs == NULL) {
		fp = org_fp;
		goto out_addrs;
	}

	memset(&cgctx, 0, sizeof(struct codegen_context));
	bpf_jit_init_reg_mapping(&cgctx);

	/* Make sure that the stack is quadword aligned. */
	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)) {
		/* We hit something illegal or unsupported. */
		fp = org_fp;
		goto out_addrs;
	}

	/*
	 * If we have seen a tail call, we need a second pass.
	 * This is because bpf_jit_emit_common_epilogue() is called
	 * from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
	 * We also need a second pass if we ended up with too large
	 * a program so as to ensure BPF_EXIT branches are in range.
	 */
	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)) {
			fp = org_fp;
			goto out_addrs;
		}
	}

	bpf_jit_realloc_regs(&cgctx);
	/*
	 * Pretend to build prologue, given the features we've seen.  This will
	 * update ctgtx.idx as it pretends to output instructions, then we can
	 * calculate total size from idx.
	 */
	bpf_jit_build_prologue(0, &cgctx);
	addrs[fp->len] = cgctx.idx * 4;
	bpf_jit_build_epilogue(0, &cgctx);

	fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
	extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);

	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) {
		fp = org_fp;
		goto out_addrs;
	}

	if (extable_len)
		fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len;

skip_init_ctx:
	code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);

	if (extra_pass) {
		/*
		 * Do not touch the prologue and epilogue as they will remain
		 * unchanged. Only fix the branch target address for subprog
		 * calls in the body, and ldimm64 instructions.
		 *
		 * This does not change the offsets and lengths of the subprog
		 * call instruction sequences and hence, the size of the JITed
		 * image as well.
		 */
		bpf_jit_fixup_addresses(fp, code_base, &cgctx, addrs);

		/* There is no need to perform the usual passes. */
		goto skip_codegen_passes;
	}

	/* Code generation passes 1-2 */
	for (pass = 1; pass < 3; pass++) {
		/* Now build the prologue, body code & epilogue for real. */
		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)) {
			bpf_jit_binary_free(bpf_hdr);
			fp = org_fp;
			goto out_addrs;
		}
		bpf_jit_build_epilogue(code_base, &cgctx);

		if (bpf_jit_enable > 1)
			pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
				proglen - (cgctx.idx * 4), cgctx.seen);
	}

skip_codegen_passes:
	if (bpf_jit_enable > 1)
		/*
		 * 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);

#ifdef CONFIG_PPC64_ELF_ABI_V1
	/* Function descriptor nastiness: Address + TOC */
	((u64 *)image)[0] = (u64)code_base;
	((u64 *)image)[1] = local_paca->kernel_toc;
#endif

	fp->bpf_func = (void *)image;
	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);
		bpf_prog_fill_jited_linfo(fp, addrs);
out_addrs:
		kfree(addrs);
		kfree(jit_data);
		fp->aux->jit_data = NULL;
	} else {
		jit_data->addrs = addrs;
		jit_data->ctx = cgctx;
		jit_data->proglen = proglen;
		jit_data->image = image;
		jit_data->header = bpf_hdr;
	}

out:
	if (bpf_blinded)
		bpf_jit_prog_release_other(fp, fp == org_fp ? tmp_fp : org_fp);

	return 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)
{
	off_t offset;
	unsigned long pc;
	struct exception_table_entry *ex;
	u32 *fixup;

	/* Populate extable entries only in the last pass */
	if (pass != 2)
		return 0;

	if (!fp->aux->extable ||
	    WARN_ON_ONCE(ctx->exentry_idx >= fp->aux->num_exentries))
		return -EINVAL;

	pc = (unsigned long)&image[insn_idx];

	fixup = (void *)fp->aux->extable -
		(fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
		(ctx->exentry_idx * BPF_FIXUP_LEN * 4);

	fixup[0] = PPC_RAW_LI(dst_reg, 0);
	if (IS_ENABLED(CONFIG_PPC32))
		fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */

	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];

	offset = pc - (long)&ex->insn;
	if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
		return -ERANGE;
	ex->insn = offset;

	offset = (long)fixup - (long)&ex->fixup;
	if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
		return -ERANGE;
	ex->fixup = offset;

	ctx->exentry_idx++;
	return 0;
}