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/*
* Decoder of classic BPF programs.
*
* Copyright (c) 2015-2017 Dmitry V. Levin <ldv@altlinux.org>
* Copyright (c) 2017-2018 The strace developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "defs.h"
#include "bpf_filter.h"
#include "bpf_fprog.h"
#include <linux/filter.h>
#include "xlat/bpf_class.h"
#include "xlat/bpf_miscop.h"
#include "xlat/bpf_mode.h"
#include "xlat/bpf_op_alu.h"
#include "xlat/bpf_op_jmp.h"
#include "xlat/bpf_rval.h"
#include "xlat/bpf_size.h"
#include "xlat/bpf_src.h"
#include "xlat/ebpf_class.h"
#include "xlat/ebpf_mode.h"
#include "xlat/ebpf_op_alu.h"
#include "xlat/ebpf_op_jmp.h"
#include "xlat/ebpf_size.h"
void
print_bpf_filter_code(const uint16_t code, bool extended)
{
const struct xlat *mode = extended ? ebpf_mode : bpf_mode;
uint16_t i = code & ~BPF_CLASS(code);
if (extended)
printxval_index(ebpf_class, BPF_CLASS(code), "BPF_???");
else
printxval_index(bpf_class, BPF_CLASS(code), "BPF_???");
switch (BPF_CLASS(code)) {
case BPF_ST:
case BPF_STX:
if (!extended) {
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
ATTRIBUTE_FALLTHROUGH; /* extended == true */
case BPF_LD:
case BPF_LDX:
tprints("|");
printxvals(BPF_SIZE(code), "BPF_???",
bpf_size, extended ? ebpf_size : NULL, NULL);
tprints("|");
printxval(mode, BPF_MODE(code), "BPF_???");
break;
case BPF_MISC: /* BPF_ALU64 in eBPF */
if (!extended) {
tprints("|");
printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
i &= ~BPF_MISCOP(code);
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
ATTRIBUTE_FALLTHROUGH; /* extended == true */
case BPF_ALU:
tprints("|");
printxval(bpf_src, BPF_SRC(code), "BPF_???");
tprints("|");
printxvals(BPF_OP(code), "BPF_???",
bpf_op_alu,
extended ? ebpf_op_alu : NULL, NULL);
break;
case BPF_JMP:
tprints("|");
printxval(bpf_src, BPF_SRC(code), "BPF_???");
tprints("|");
printxvals(BPF_OP(code), "BPF_???",
bpf_op_jmp, extended ? ebpf_op_jmp : NULL, NULL);
break;
case BPF_RET: /* Reserved in eBPF */
if (!extended) {
tprints("|");
printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
i &= ~BPF_RVAL(code);
}
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
}
static void
print_bpf_filter_stmt(const struct bpf_filter_block *const filter,
const print_bpf_filter_fn print_k)
{
tprints("BPF_STMT(");
print_bpf_filter_code(filter->code, false);
tprints(", ");
if (!print_k || !print_k(filter))
tprintf("%#x", filter->k);
tprints(")");
}
static void
print_bpf_filter_jump(const struct bpf_filter_block *const filter)
{
tprints("BPF_JUMP(");
print_bpf_filter_code(filter->code, false);
tprintf(", %#x, %#x, %#x)", filter->k, filter->jt, filter->jf);
}
struct bpf_filter_block_data {
const print_bpf_filter_fn fn;
unsigned int count;
};
static bool
print_bpf_filter_block(struct tcb *const tcp, void *const elem_buf,
const size_t elem_size, void *const data)
{
const struct bpf_filter_block *const filter = elem_buf;
struct bpf_filter_block_data *const fbd = data;
if (fbd->count++ >= BPF_MAXINSNS) {
tprints("...");
return false;
}
if (filter->jt || filter->jf)
print_bpf_filter_jump(filter);
else
print_bpf_filter_stmt(filter, fbd->fn);
return true;
}
void
print_bpf_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
const unsigned short len, const print_bpf_filter_fn print_k)
{
if (abbrev(tcp)) {
printaddr(addr);
} else {
struct bpf_filter_block_data fbd = { .fn = print_k };
struct bpf_filter_block filter;
print_array(tcp, addr, len, &filter, sizeof(filter),
tfetch_mem, print_bpf_filter_block, &fbd);
}
}
void
decode_bpf_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
const print_bpf_filter_fn print_k)
{
struct bpf_fprog fprog;
if (fetch_bpf_fprog(tcp, addr, &fprog)) {
tprintf("{len=%hu, filter=", fprog.len);
print_bpf_fprog(tcp, fprog.filter, fprog.len, print_k);
tprints("}");
}
}
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