mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-24 17:59:32 +00:00
![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
As we move stuff around, some doc references are broken. Fix some of them via this script: ./scripts/documentation-file-ref-check --fix Manually checked if the produced result is valid, removing a few false-positives. Acked-by: Takashi Iwai <tiwai@suse.de> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Stephen Boyd <sboyd@kernel.org> Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com> Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org> Reviewed-by: Coly Li <colyli@suse.de> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Jonathan Corbet <corbet@lwn.net>
502 lines
12 KiB
C
502 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* bpf-prologue.c
|
|
*
|
|
* Copyright (C) 2015 He Kuang <hekuang@huawei.com>
|
|
* Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
|
|
* Copyright (C) 2015 Huawei Inc.
|
|
*/
|
|
|
|
#include <bpf/libbpf.h>
|
|
#include "perf.h"
|
|
#include "debug.h"
|
|
#include "bpf-loader.h"
|
|
#include "bpf-prologue.h"
|
|
#include "probe-finder.h"
|
|
#include <errno.h>
|
|
#include <dwarf-regs.h>
|
|
#include <linux/filter.h>
|
|
|
|
#define BPF_REG_SIZE 8
|
|
|
|
#define JMP_TO_ERROR_CODE -1
|
|
#define JMP_TO_SUCCESS_CODE -2
|
|
#define JMP_TO_USER_CODE -3
|
|
|
|
struct bpf_insn_pos {
|
|
struct bpf_insn *begin;
|
|
struct bpf_insn *end;
|
|
struct bpf_insn *pos;
|
|
};
|
|
|
|
static inline int
|
|
pos_get_cnt(struct bpf_insn_pos *pos)
|
|
{
|
|
return pos->pos - pos->begin;
|
|
}
|
|
|
|
static int
|
|
append_insn(struct bpf_insn new_insn, struct bpf_insn_pos *pos)
|
|
{
|
|
if (!pos->pos)
|
|
return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
|
|
|
|
if (pos->pos + 1 >= pos->end) {
|
|
pr_err("bpf prologue: prologue too long\n");
|
|
pos->pos = NULL;
|
|
return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
|
|
}
|
|
|
|
*(pos->pos)++ = new_insn;
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
check_pos(struct bpf_insn_pos *pos)
|
|
{
|
|
if (!pos->pos || pos->pos >= pos->end)
|
|
return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Convert type string (u8/u16/u32/u64/s8/s16/s32/s64 ..., see
|
|
* Documentation/trace/kprobetrace.rst) to size field of BPF_LDX_MEM
|
|
* instruction (BPF_{B,H,W,DW}).
|
|
*/
|
|
static int
|
|
argtype_to_ldx_size(const char *type)
|
|
{
|
|
int arg_size = type ? atoi(&type[1]) : 64;
|
|
|
|
switch (arg_size) {
|
|
case 8:
|
|
return BPF_B;
|
|
case 16:
|
|
return BPF_H;
|
|
case 32:
|
|
return BPF_W;
|
|
case 64:
|
|
default:
|
|
return BPF_DW;
|
|
}
|
|
}
|
|
|
|
static const char *
|
|
insn_sz_to_str(int insn_sz)
|
|
{
|
|
switch (insn_sz) {
|
|
case BPF_B:
|
|
return "BPF_B";
|
|
case BPF_H:
|
|
return "BPF_H";
|
|
case BPF_W:
|
|
return "BPF_W";
|
|
case BPF_DW:
|
|
return "BPF_DW";
|
|
default:
|
|
return "UNKNOWN";
|
|
}
|
|
}
|
|
|
|
/* Give it a shorter name */
|
|
#define ins(i, p) append_insn((i), (p))
|
|
|
|
/*
|
|
* Give a register name (in 'reg'), generate instruction to
|
|
* load register into an eBPF register rd:
|
|
* 'ldd target_reg, offset(ctx_reg)', where:
|
|
* ctx_reg is pre initialized to pointer of 'struct pt_regs'.
|
|
*/
|
|
static int
|
|
gen_ldx_reg_from_ctx(struct bpf_insn_pos *pos, int ctx_reg,
|
|
const char *reg, int target_reg)
|
|
{
|
|
int offset = regs_query_register_offset(reg);
|
|
|
|
if (offset < 0) {
|
|
pr_err("bpf: prologue: failed to get register %s\n",
|
|
reg);
|
|
return offset;
|
|
}
|
|
ins(BPF_LDX_MEM(BPF_DW, target_reg, ctx_reg, offset), pos);
|
|
|
|
return check_pos(pos);
|
|
}
|
|
|
|
/*
|
|
* Generate a BPF_FUNC_probe_read function call.
|
|
*
|
|
* src_base_addr_reg is a register holding base address,
|
|
* dst_addr_reg is a register holding dest address (on stack),
|
|
* result is:
|
|
*
|
|
* *[dst_addr_reg] = *([src_base_addr_reg] + offset)
|
|
*
|
|
* Arguments of BPF_FUNC_probe_read:
|
|
* ARG1: ptr to stack (dest)
|
|
* ARG2: size (8)
|
|
* ARG3: unsafe ptr (src)
|
|
*/
|
|
static int
|
|
gen_read_mem(struct bpf_insn_pos *pos,
|
|
int src_base_addr_reg,
|
|
int dst_addr_reg,
|
|
long offset)
|
|
{
|
|
/* mov arg3, src_base_addr_reg */
|
|
if (src_base_addr_reg != BPF_REG_ARG3)
|
|
ins(BPF_MOV64_REG(BPF_REG_ARG3, src_base_addr_reg), pos);
|
|
/* add arg3, #offset */
|
|
if (offset)
|
|
ins(BPF_ALU64_IMM(BPF_ADD, BPF_REG_ARG3, offset), pos);
|
|
|
|
/* mov arg2, #reg_size */
|
|
ins(BPF_ALU64_IMM(BPF_MOV, BPF_REG_ARG2, BPF_REG_SIZE), pos);
|
|
|
|
/* mov arg1, dst_addr_reg */
|
|
if (dst_addr_reg != BPF_REG_ARG1)
|
|
ins(BPF_MOV64_REG(BPF_REG_ARG1, dst_addr_reg), pos);
|
|
|
|
/* Call probe_read */
|
|
ins(BPF_EMIT_CALL(BPF_FUNC_probe_read), pos);
|
|
/*
|
|
* Error processing: if read fail, goto error code,
|
|
* will be relocated. Target should be the start of
|
|
* error processing code.
|
|
*/
|
|
ins(BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, JMP_TO_ERROR_CODE),
|
|
pos);
|
|
|
|
return check_pos(pos);
|
|
}
|
|
|
|
/*
|
|
* Each arg should be bare register. Fetch and save them into argument
|
|
* registers (r3 - r5).
|
|
*
|
|
* BPF_REG_1 should have been initialized with pointer to
|
|
* 'struct pt_regs'.
|
|
*/
|
|
static int
|
|
gen_prologue_fastpath(struct bpf_insn_pos *pos,
|
|
struct probe_trace_arg *args, int nargs)
|
|
{
|
|
int i, err = 0;
|
|
|
|
for (i = 0; i < nargs; i++) {
|
|
err = gen_ldx_reg_from_ctx(pos, BPF_REG_1, args[i].value,
|
|
BPF_PROLOGUE_START_ARG_REG + i);
|
|
if (err)
|
|
goto errout;
|
|
}
|
|
|
|
return check_pos(pos);
|
|
errout:
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* Slow path:
|
|
* At least one argument has the form of 'offset($rx)'.
|
|
*
|
|
* Following code first stores them into stack, then loads all of then
|
|
* to r2 - r5.
|
|
* Before final loading, the final result should be:
|
|
*
|
|
* low address
|
|
* BPF_REG_FP - 24 ARG3
|
|
* BPF_REG_FP - 16 ARG2
|
|
* BPF_REG_FP - 8 ARG1
|
|
* BPF_REG_FP
|
|
* high address
|
|
*
|
|
* For each argument (described as: offn(...off2(off1(reg)))),
|
|
* generates following code:
|
|
*
|
|
* r7 <- fp
|
|
* r7 <- r7 - stack_offset // Ideal code should initialize r7 using
|
|
* // fp before generating args. However,
|
|
* // eBPF won't regard r7 as stack pointer
|
|
* // if it is generated by minus 8 from
|
|
* // another stack pointer except fp.
|
|
* // This is why we have to set r7
|
|
* // to fp for each variable.
|
|
* r3 <- value of 'reg'-> generated using gen_ldx_reg_from_ctx()
|
|
* (r7) <- r3 // skip following instructions for bare reg
|
|
* r3 <- r3 + off1 . // skip if off1 == 0
|
|
* r2 <- 8 \
|
|
* r1 <- r7 |-> generated by gen_read_mem()
|
|
* call probe_read /
|
|
* jnei r0, 0, err ./
|
|
* r3 <- (r7)
|
|
* r3 <- r3 + off2 . // skip if off2 == 0
|
|
* r2 <- 8 \ // r2 may be broken by probe_read, so set again
|
|
* r1 <- r7 |-> generated by gen_read_mem()
|
|
* call probe_read /
|
|
* jnei r0, 0, err ./
|
|
* ...
|
|
*/
|
|
static int
|
|
gen_prologue_slowpath(struct bpf_insn_pos *pos,
|
|
struct probe_trace_arg *args, int nargs)
|
|
{
|
|
int err, i;
|
|
|
|
for (i = 0; i < nargs; i++) {
|
|
struct probe_trace_arg *arg = &args[i];
|
|
const char *reg = arg->value;
|
|
struct probe_trace_arg_ref *ref = NULL;
|
|
int stack_offset = (i + 1) * -8;
|
|
|
|
pr_debug("prologue: fetch arg %d, base reg is %s\n",
|
|
i, reg);
|
|
|
|
/* value of base register is stored into ARG3 */
|
|
err = gen_ldx_reg_from_ctx(pos, BPF_REG_CTX, reg,
|
|
BPF_REG_ARG3);
|
|
if (err) {
|
|
pr_err("prologue: failed to get offset of register %s\n",
|
|
reg);
|
|
goto errout;
|
|
}
|
|
|
|
/* Make r7 the stack pointer. */
|
|
ins(BPF_MOV64_REG(BPF_REG_7, BPF_REG_FP), pos);
|
|
/* r7 += -8 */
|
|
ins(BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, stack_offset), pos);
|
|
/*
|
|
* Store r3 (base register) onto stack
|
|
* Ensure fp[offset] is set.
|
|
* fp is the only valid base register when storing
|
|
* into stack. We are not allowed to use r7 as base
|
|
* register here.
|
|
*/
|
|
ins(BPF_STX_MEM(BPF_DW, BPF_REG_FP, BPF_REG_ARG3,
|
|
stack_offset), pos);
|
|
|
|
ref = arg->ref;
|
|
while (ref) {
|
|
pr_debug("prologue: arg %d: offset %ld\n",
|
|
i, ref->offset);
|
|
err = gen_read_mem(pos, BPF_REG_3, BPF_REG_7,
|
|
ref->offset);
|
|
if (err) {
|
|
pr_err("prologue: failed to generate probe_read function call\n");
|
|
goto errout;
|
|
}
|
|
|
|
ref = ref->next;
|
|
/*
|
|
* Load previous result into ARG3. Use
|
|
* BPF_REG_FP instead of r7 because verifier
|
|
* allows FP based addressing only.
|
|
*/
|
|
if (ref)
|
|
ins(BPF_LDX_MEM(BPF_DW, BPF_REG_ARG3,
|
|
BPF_REG_FP, stack_offset), pos);
|
|
}
|
|
}
|
|
|
|
/* Final pass: read to registers */
|
|
for (i = 0; i < nargs; i++) {
|
|
int insn_sz = (args[i].ref) ? argtype_to_ldx_size(args[i].type) : BPF_DW;
|
|
|
|
pr_debug("prologue: load arg %d, insn_sz is %s\n",
|
|
i, insn_sz_to_str(insn_sz));
|
|
ins(BPF_LDX_MEM(insn_sz, BPF_PROLOGUE_START_ARG_REG + i,
|
|
BPF_REG_FP, -BPF_REG_SIZE * (i + 1)), pos);
|
|
}
|
|
|
|
ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_SUCCESS_CODE), pos);
|
|
|
|
return check_pos(pos);
|
|
errout:
|
|
return err;
|
|
}
|
|
|
|
static int
|
|
prologue_relocate(struct bpf_insn_pos *pos, struct bpf_insn *error_code,
|
|
struct bpf_insn *success_code, struct bpf_insn *user_code)
|
|
{
|
|
struct bpf_insn *insn;
|
|
|
|
if (check_pos(pos))
|
|
return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
|
|
|
|
for (insn = pos->begin; insn < pos->pos; insn++) {
|
|
struct bpf_insn *target;
|
|
u8 class = BPF_CLASS(insn->code);
|
|
u8 opcode;
|
|
|
|
if (class != BPF_JMP)
|
|
continue;
|
|
opcode = BPF_OP(insn->code);
|
|
if (opcode == BPF_CALL)
|
|
continue;
|
|
|
|
switch (insn->off) {
|
|
case JMP_TO_ERROR_CODE:
|
|
target = error_code;
|
|
break;
|
|
case JMP_TO_SUCCESS_CODE:
|
|
target = success_code;
|
|
break;
|
|
case JMP_TO_USER_CODE:
|
|
target = user_code;
|
|
break;
|
|
default:
|
|
pr_err("bpf prologue: internal error: relocation failed\n");
|
|
return -BPF_LOADER_ERRNO__PROLOGUE;
|
|
}
|
|
|
|
insn->off = target - (insn + 1);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
int bpf__gen_prologue(struct probe_trace_arg *args, int nargs,
|
|
struct bpf_insn *new_prog, size_t *new_cnt,
|
|
size_t cnt_space)
|
|
{
|
|
struct bpf_insn *success_code = NULL;
|
|
struct bpf_insn *error_code = NULL;
|
|
struct bpf_insn *user_code = NULL;
|
|
struct bpf_insn_pos pos;
|
|
bool fastpath = true;
|
|
int err = 0, i;
|
|
|
|
if (!new_prog || !new_cnt)
|
|
return -EINVAL;
|
|
|
|
if (cnt_space > BPF_MAXINSNS)
|
|
cnt_space = BPF_MAXINSNS;
|
|
|
|
pos.begin = new_prog;
|
|
pos.end = new_prog + cnt_space;
|
|
pos.pos = new_prog;
|
|
|
|
if (!nargs) {
|
|
ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 0),
|
|
&pos);
|
|
|
|
if (check_pos(&pos))
|
|
goto errout;
|
|
|
|
*new_cnt = pos_get_cnt(&pos);
|
|
return 0;
|
|
}
|
|
|
|
if (nargs > BPF_PROLOGUE_MAX_ARGS) {
|
|
pr_warning("bpf: prologue: %d arguments are dropped\n",
|
|
nargs - BPF_PROLOGUE_MAX_ARGS);
|
|
nargs = BPF_PROLOGUE_MAX_ARGS;
|
|
}
|
|
|
|
/* First pass: validation */
|
|
for (i = 0; i < nargs; i++) {
|
|
struct probe_trace_arg_ref *ref = args[i].ref;
|
|
|
|
if (args[i].value[0] == '@') {
|
|
/* TODO: fetch global variable */
|
|
pr_err("bpf: prologue: global %s%+ld not support\n",
|
|
args[i].value, ref ? ref->offset : 0);
|
|
return -ENOTSUP;
|
|
}
|
|
|
|
while (ref) {
|
|
/* fastpath is true if all args has ref == NULL */
|
|
fastpath = false;
|
|
|
|
/*
|
|
* Instruction encodes immediate value using
|
|
* s32, ref->offset is long. On systems which
|
|
* can't fill long in s32, refuse to process if
|
|
* ref->offset too large (or small).
|
|
*/
|
|
#ifdef __LP64__
|
|
#define OFFSET_MAX ((1LL << 31) - 1)
|
|
#define OFFSET_MIN ((1LL << 31) * -1)
|
|
if (ref->offset > OFFSET_MAX ||
|
|
ref->offset < OFFSET_MIN) {
|
|
pr_err("bpf: prologue: offset out of bound: %ld\n",
|
|
ref->offset);
|
|
return -BPF_LOADER_ERRNO__PROLOGUEOOB;
|
|
}
|
|
#endif
|
|
ref = ref->next;
|
|
}
|
|
}
|
|
pr_debug("prologue: pass validation\n");
|
|
|
|
if (fastpath) {
|
|
/* If all variables are registers... */
|
|
pr_debug("prologue: fast path\n");
|
|
err = gen_prologue_fastpath(&pos, args, nargs);
|
|
if (err)
|
|
goto errout;
|
|
} else {
|
|
pr_debug("prologue: slow path\n");
|
|
|
|
/* Initialization: move ctx to a callee saved register. */
|
|
ins(BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1), &pos);
|
|
|
|
err = gen_prologue_slowpath(&pos, args, nargs);
|
|
if (err)
|
|
goto errout;
|
|
/*
|
|
* start of ERROR_CODE (only slow pass needs error code)
|
|
* mov r2 <- 1 // r2 is error number
|
|
* mov r3 <- 0 // r3, r4... should be touched or
|
|
* // verifier would complain
|
|
* mov r4 <- 0
|
|
* ...
|
|
* goto usercode
|
|
*/
|
|
error_code = pos.pos;
|
|
ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 1),
|
|
&pos);
|
|
|
|
for (i = 0; i < nargs; i++)
|
|
ins(BPF_ALU64_IMM(BPF_MOV,
|
|
BPF_PROLOGUE_START_ARG_REG + i,
|
|
0),
|
|
&pos);
|
|
ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_USER_CODE),
|
|
&pos);
|
|
}
|
|
|
|
/*
|
|
* start of SUCCESS_CODE:
|
|
* mov r2 <- 0
|
|
* goto usercode // skip
|
|
*/
|
|
success_code = pos.pos;
|
|
ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 0), &pos);
|
|
|
|
/*
|
|
* start of USER_CODE:
|
|
* Restore ctx to r1
|
|
*/
|
|
user_code = pos.pos;
|
|
if (!fastpath) {
|
|
/*
|
|
* Only slow path needs restoring of ctx. In fast path,
|
|
* register are loaded directly from r1.
|
|
*/
|
|
ins(BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX), &pos);
|
|
err = prologue_relocate(&pos, error_code, success_code,
|
|
user_code);
|
|
if (err)
|
|
goto errout;
|
|
}
|
|
|
|
err = check_pos(&pos);
|
|
if (err)
|
|
goto errout;
|
|
|
|
*new_cnt = pos_get_cnt(&pos);
|
|
return 0;
|
|
errout:
|
|
return err;
|
|
}
|