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linux/kernel/bpf/disasm.c
Brendan Jackman 5ca419f286 bpf: Add BPF_FETCH field / create atomic_fetch_add instruction 
The BPF_FETCH field can be set in bpf_insn.imm, for BPF_ATOMIC
instructions, in order to have the previous value of the
atomically-modified memory location loaded into the src register
after an atomic op is carried out.

Suggested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-7-jackmanb@google.com
2021-01-14 18:34:29 -08:00

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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
*/
#include <linux/bpf.h>
#include "disasm.h"
#define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x)
static const char * const func_id_str[] = {
__BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN)
};
#undef __BPF_FUNC_STR_FN
static const char *__func_get_name(const struct bpf_insn_cbs *cbs,
const struct bpf_insn *insn,
char *buff, size_t len)
{
BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID);
if (insn->src_reg != BPF_PSEUDO_CALL &&
insn->imm >= 0 && insn->imm < __BPF_FUNC_MAX_ID &&
func_id_str[insn->imm])
return func_id_str[insn->imm];
if (cbs && cbs->cb_call)
return cbs->cb_call(cbs->private_data, insn);
if (insn->src_reg == BPF_PSEUDO_CALL)
snprintf(buff, len, "%+d", insn->imm);
return buff;
}
static const char *__func_imm_name(const struct bpf_insn_cbs *cbs,
const struct bpf_insn *insn,
u64 full_imm, char *buff, size_t len)
{
if (cbs && cbs->cb_imm)
return cbs->cb_imm(cbs->private_data, insn, full_imm);
snprintf(buff, len, "0x%llx", (unsigned long long)full_imm);
return buff;
}
const char *func_id_name(int id)
{
if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id])
return func_id_str[id];
else
return "unknown";
}
const char *const bpf_class_string[8] = {
[BPF_LD] = "ld",
[BPF_LDX] = "ldx",
[BPF_ST] = "st",
[BPF_STX] = "stx",
[BPF_ALU] = "alu",
[BPF_JMP] = "jmp",
[BPF_JMP32] = "jmp32",
[BPF_ALU64] = "alu64",
};
const char *const bpf_alu_string[16] = {
[BPF_ADD >> 4] = "+=",
[BPF_SUB >> 4] = "-=",
[BPF_MUL >> 4] = "*=",
[BPF_DIV >> 4] = "/=",
[BPF_OR >> 4] = "|=",
[BPF_AND >> 4] = "&=",
[BPF_LSH >> 4] = "<<=",
[BPF_RSH >> 4] = ">>=",
[BPF_NEG >> 4] = "neg",
[BPF_MOD >> 4] = "%=",
[BPF_XOR >> 4] = "^=",
[BPF_MOV >> 4] = "=",
[BPF_ARSH >> 4] = "s>>=",
[BPF_END >> 4] = "endian",
};
static const char *const bpf_ldst_string[] = {
[BPF_W >> 3] = "u32",
[BPF_H >> 3] = "u16",
[BPF_B >> 3] = "u8",
[BPF_DW >> 3] = "u64",
};
static const char *const bpf_jmp_string[16] = {
[BPF_JA >> 4] = "jmp",
[BPF_JEQ >> 4] = "==",
[BPF_JGT >> 4] = ">",
[BPF_JLT >> 4] = "<",
[BPF_JGE >> 4] = ">=",
[BPF_JLE >> 4] = "<=",
[BPF_JSET >> 4] = "&",
[BPF_JNE >> 4] = "!=",
[BPF_JSGT >> 4] = "s>",
[BPF_JSLT >> 4] = "s<",
[BPF_JSGE >> 4] = "s>=",
[BPF_JSLE >> 4] = "s<=",
[BPF_CALL >> 4] = "call",
[BPF_EXIT >> 4] = "exit",
};
static void print_bpf_end_insn(bpf_insn_print_t verbose,
void *private_data,
const struct bpf_insn *insn)
{
verbose(private_data, "(%02x) r%d = %s%d r%d\n",
insn->code, insn->dst_reg,
BPF_SRC(insn->code) == BPF_TO_BE ? "be" : "le",
insn->imm, insn->dst_reg);
}
void print_bpf_insn(const struct bpf_insn_cbs *cbs,
const struct bpf_insn *insn,
bool allow_ptr_leaks)
{
const bpf_insn_print_t verbose = cbs->cb_print;
u8 class = BPF_CLASS(insn->code);
if (class == BPF_ALU || class == BPF_ALU64) {
if (BPF_OP(insn->code) == BPF_END) {
if (class == BPF_ALU64)
verbose(cbs->private_data, "BUG_alu64_%02x\n", insn->code);
else
print_bpf_end_insn(verbose, cbs->private_data, insn);
} else if (BPF_OP(insn->code) == BPF_NEG) {
verbose(cbs->private_data, "(%02x) %c%d = -%c%d\n",
insn->code, class == BPF_ALU ? 'w' : 'r',
insn->dst_reg, class == BPF_ALU ? 'w' : 'r',
insn->dst_reg);
} else if (BPF_SRC(insn->code) == BPF_X) {
verbose(cbs->private_data, "(%02x) %c%d %s %c%d\n",
insn->code, class == BPF_ALU ? 'w' : 'r',
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? 'w' : 'r',
insn->src_reg);
} else {
verbose(cbs->private_data, "(%02x) %c%d %s %d\n",
insn->code, class == BPF_ALU ? 'w' : 'r',
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
insn->imm);
}
} else if (class == BPF_STX) {
if (BPF_MODE(insn->code) == BPF_MEM)
verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->src_reg);
else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
insn->imm == BPF_ADD) {
verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) += r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off,
insn->src_reg);
} else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
insn->imm == (BPF_ADD | BPF_FETCH)) {
verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_add((%s *)(r%d %+d), r%d)\n",
insn->code, insn->src_reg,
BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off, insn->src_reg);
} else {
verbose(cbs->private_data, "BUG_%02x\n", insn->code);
}
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose(cbs->private_data, "BUG_st_%02x\n", insn->code);
return;
}
verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->imm);
} else if (class == BPF_LDX) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose(cbs->private_data, "BUG_ldx_%02x\n", insn->code);
return;
}
verbose(cbs->private_data, "(%02x) r%d = *(%s *)(r%d %+d)\n",
insn->code, insn->dst_reg,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->off);
} else if (class == BPF_LD) {
if (BPF_MODE(insn->code) == BPF_ABS) {
verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[%d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IND) {
verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[r%d + %d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IMM &&
BPF_SIZE(insn->code) == BPF_DW) {
/* At this point, we already made sure that the second
* part of the ldimm64 insn is accessible.
*/
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
bool is_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD ||
insn->src_reg == BPF_PSEUDO_MAP_VALUE;
char tmp[64];
if (is_ptr && !allow_ptr_leaks)
imm = 0;
verbose(cbs->private_data, "(%02x) r%d = %s\n",
insn->code, insn->dst_reg,
__func_imm_name(cbs, insn, imm,
tmp, sizeof(tmp)));
} else {
verbose(cbs->private_data, "BUG_ld_%02x\n", insn->code);
return;
}
} else if (class == BPF_JMP32 || class == BPF_JMP) {
u8 opcode = BPF_OP(insn->code);
if (opcode == BPF_CALL) {
char tmp[64];
if (insn->src_reg == BPF_PSEUDO_CALL) {
verbose(cbs->private_data, "(%02x) call pc%s\n",
insn->code,
__func_get_name(cbs, insn,
tmp, sizeof(tmp)));
} else {
strcpy(tmp, "unknown");
verbose(cbs->private_data, "(%02x) call %s#%d\n", insn->code,
__func_get_name(cbs, insn,
tmp, sizeof(tmp)),
insn->imm);
}
} else if (insn->code == (BPF_JMP | BPF_JA)) {
verbose(cbs->private_data, "(%02x) goto pc%+d\n",
insn->code, insn->off);
} else if (insn->code == (BPF_JMP | BPF_EXIT)) {
verbose(cbs->private_data, "(%02x) exit\n", insn->code);
} else if (BPF_SRC(insn->code) == BPF_X) {
verbose(cbs->private_data,
"(%02x) if %c%d %s %c%d goto pc%+d\n",
insn->code, class == BPF_JMP32 ? 'w' : 'r',
insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
class == BPF_JMP32 ? 'w' : 'r',
insn->src_reg, insn->off);
} else {
verbose(cbs->private_data,
"(%02x) if %c%d %s 0x%x goto pc%+d\n",
insn->code, class == BPF_JMP32 ? 'w' : 'r',
insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->imm, insn->off);
}
} else {
verbose(cbs->private_data, "(%02x) %s\n",
insn->code, bpf_class_string[class]);
}
}
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