linux/kernel/trace/bpf_trace.c
Daniel Borkmann f3694e0012 bpf: add BPF_CALL_x macros for declaring helpers
This work adds BPF_CALL_<n>() macros and converts all the eBPF helper functions
to use them, in a similar fashion like we do with SYSCALL_DEFINE<n>() macros
that are used today. Motivation for this is to hide all the register handling
and all necessary casts from the user, so that it is done automatically in the
background when adding a BPF_CALL_<n>() call.

This makes current helpers easier to review, eases to write future helpers,
avoids getting the casting mess wrong, and allows for extending all helpers at
once (f.e. build time checks, etc). It also helps detecting more easily in
code reviews that unused registers are not instrumented in the code by accident,
breaking compatibility with existing programs.

BPF_CALL_<n>() internals are quite similar to SYSCALL_DEFINE<n>() ones with some
fundamental differences, for example, for generating the actual helper function
that carries all u64 regs, we need to fill unused regs, so that we always end up
with 5 u64 regs as an argument.

I reviewed several 0-5 generated BPF_CALL_<n>() variants of the .i results and
they look all as expected. No sparse issue spotted. We let this also sit for a
few days with Fengguang's kbuild test robot, and there were no issues seen. On
s390, it barked on the "uses dynamic stack allocation" notice, which is an old
one from bpf_perf_event_output{,_tp}() reappearing here due to the conversion
to the call wrapper, just telling that the perf raw record/frag sits on stack
(gcc with s390's -mwarn-dynamicstack), but that's all. Did various runtime tests
and they were fine as well. All eBPF helpers are now converted to use these
macros, getting rid of a good chunk of all the raw castings.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-09-09 19:36:04 -07:00

620 lines
16 KiB
C

/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_perf_event.h>
#include <linux/filter.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include "trace.h"
/**
* trace_call_bpf - invoke BPF program
* @prog: BPF program
* @ctx: opaque context pointer
*
* kprobe handlers execute BPF programs via this helper.
* Can be used from static tracepoints in the future.
*
* Return: BPF programs always return an integer which is interpreted by
* kprobe handler as:
* 0 - return from kprobe (event is filtered out)
* 1 - store kprobe event into ring buffer
* Other values are reserved and currently alias to 1
*/
unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
{
unsigned int ret;
if (in_nmi()) /* not supported yet */
return 1;
preempt_disable();
if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
/*
* since some bpf program is already running on this cpu,
* don't call into another bpf program (same or different)
* and don't send kprobe event into ring-buffer,
* so return zero here
*/
ret = 0;
goto out;
}
rcu_read_lock();
ret = BPF_PROG_RUN(prog, ctx);
rcu_read_unlock();
out:
__this_cpu_dec(bpf_prog_active);
preempt_enable();
return ret;
}
EXPORT_SYMBOL_GPL(trace_call_bpf);
BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
{
int ret;
ret = probe_kernel_read(dst, unsafe_ptr, size);
if (unlikely(ret < 0))
memset(dst, 0, size);
return ret;
}
static const struct bpf_func_proto bpf_probe_read_proto = {
.func = bpf_probe_read,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_RAW_STACK,
.arg2_type = ARG_CONST_STACK_SIZE,
.arg3_type = ARG_ANYTHING,
};
BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
u32, size)
{
/*
* Ensure we're in user context which is safe for the helper to
* run. This helper has no business in a kthread.
*
* access_ok() should prevent writing to non-user memory, but in
* some situations (nommu, temporary switch, etc) access_ok() does
* not provide enough validation, hence the check on KERNEL_DS.
*/
if (unlikely(in_interrupt() ||
current->flags & (PF_KTHREAD | PF_EXITING)))
return -EPERM;
if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
return -EPERM;
if (!access_ok(VERIFY_WRITE, unsafe_ptr, size))
return -EPERM;
return probe_kernel_write(unsafe_ptr, src, size);
}
static const struct bpf_func_proto bpf_probe_write_user_proto = {
.func = bpf_probe_write_user,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_ANYTHING,
.arg2_type = ARG_PTR_TO_STACK,
.arg3_type = ARG_CONST_STACK_SIZE,
};
static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
{
pr_warn_ratelimited("%s[%d] is installing a program with bpf_probe_write_user helper that may corrupt user memory!",
current->comm, task_pid_nr(current));
return &bpf_probe_write_user_proto;
}
/*
* limited trace_printk()
* only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
*/
BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
u64, arg2, u64, arg3)
{
bool str_seen = false;
int mod[3] = {};
int fmt_cnt = 0;
u64 unsafe_addr;
char buf[64];
int i;
/*
* bpf_check()->check_func_arg()->check_stack_boundary()
* guarantees that fmt points to bpf program stack,
* fmt_size bytes of it were initialized and fmt_size > 0
*/
if (fmt[--fmt_size] != 0)
return -EINVAL;
/* check format string for allowed specifiers */
for (i = 0; i < fmt_size; i++) {
if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
return -EINVAL;
if (fmt[i] != '%')
continue;
if (fmt_cnt >= 3)
return -EINVAL;
/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
i++;
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
} else if (fmt[i] == 'p' || fmt[i] == 's') {
mod[fmt_cnt]++;
i++;
if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
return -EINVAL;
fmt_cnt++;
if (fmt[i - 1] == 's') {
if (str_seen)
/* allow only one '%s' per fmt string */
return -EINVAL;
str_seen = true;
switch (fmt_cnt) {
case 1:
unsafe_addr = arg1;
arg1 = (long) buf;
break;
case 2:
unsafe_addr = arg2;
arg2 = (long) buf;
break;
case 3:
unsafe_addr = arg3;
arg3 = (long) buf;
break;
}
buf[0] = 0;
strncpy_from_unsafe(buf,
(void *) (long) unsafe_addr,
sizeof(buf));
}
continue;
}
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
}
if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
return -EINVAL;
fmt_cnt++;
}
return __trace_printk(1/* fake ip will not be printed */, fmt,
mod[0] == 2 ? arg1 : mod[0] == 1 ? (long) arg1 : (u32) arg1,
mod[1] == 2 ? arg2 : mod[1] == 1 ? (long) arg2 : (u32) arg2,
mod[2] == 2 ? arg3 : mod[2] == 1 ? (long) arg3 : (u32) arg3);
}
static const struct bpf_func_proto bpf_trace_printk_proto = {
.func = bpf_trace_printk,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_STACK,
.arg2_type = ARG_CONST_STACK_SIZE,
};
const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
{
/*
* this program might be calling bpf_trace_printk,
* so allocate per-cpu printk buffers
*/
trace_printk_init_buffers();
return &bpf_trace_printk_proto;
}
BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
unsigned int cpu = smp_processor_id();
u64 index = flags & BPF_F_INDEX_MASK;
struct bpf_event_entry *ee;
struct perf_event *event;
if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
return -EINVAL;
if (index == BPF_F_CURRENT_CPU)
index = cpu;
if (unlikely(index >= array->map.max_entries))
return -E2BIG;
ee = READ_ONCE(array->ptrs[index]);
if (!ee)
return -ENOENT;
event = ee->event;
if (unlikely(event->attr.type != PERF_TYPE_HARDWARE &&
event->attr.type != PERF_TYPE_RAW))
return -EINVAL;
/* make sure event is local and doesn't have pmu::count */
if (unlikely(event->oncpu != cpu || event->pmu->count))
return -EINVAL;
/*
* we don't know if the function is run successfully by the
* return value. It can be judged in other places, such as
* eBPF programs.
*/
return perf_event_read_local(event);
}
static const struct bpf_func_proto bpf_perf_event_read_proto = {
.func = bpf_perf_event_read,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_ANYTHING,
};
static __always_inline u64
__bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
u64 flags, struct perf_raw_record *raw)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
unsigned int cpu = smp_processor_id();
u64 index = flags & BPF_F_INDEX_MASK;
struct perf_sample_data sample_data;
struct bpf_event_entry *ee;
struct perf_event *event;
if (index == BPF_F_CURRENT_CPU)
index = cpu;
if (unlikely(index >= array->map.max_entries))
return -E2BIG;
ee = READ_ONCE(array->ptrs[index]);
if (!ee)
return -ENOENT;
event = ee->event;
if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
return -EINVAL;
if (unlikely(event->oncpu != cpu))
return -EOPNOTSUPP;
perf_sample_data_init(&sample_data, 0, 0);
sample_data.raw = raw;
perf_event_output(event, &sample_data, regs);
return 0;
}
BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags, void *, data, u64, size)
{
struct perf_raw_record raw = {
.frag = {
.size = size,
.data = data,
},
};
if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
return -EINVAL;
return __bpf_perf_event_output(regs, map, flags, &raw);
}
static const struct bpf_func_proto bpf_perf_event_output_proto = {
.func = bpf_perf_event_output,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
.arg4_type = ARG_PTR_TO_STACK,
.arg5_type = ARG_CONST_STACK_SIZE,
};
static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);
u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
{
struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
struct perf_raw_frag frag = {
.copy = ctx_copy,
.size = ctx_size,
.data = ctx,
};
struct perf_raw_record raw = {
.frag = {
{
.next = ctx_size ? &frag : NULL,
},
.size = meta_size,
.data = meta,
},
};
perf_fetch_caller_regs(regs);
return __bpf_perf_event_output(regs, map, flags, &raw);
}
BPF_CALL_0(bpf_get_current_task)
{
return (long) current;
}
static const struct bpf_func_proto bpf_get_current_task_proto = {
.func = bpf_get_current_task,
.gpl_only = true,
.ret_type = RET_INTEGER,
};
BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
struct cgroup *cgrp;
if (unlikely(in_interrupt()))
return -EINVAL;
if (unlikely(idx >= array->map.max_entries))
return -E2BIG;
cgrp = READ_ONCE(array->ptrs[idx]);
if (unlikely(!cgrp))
return -EAGAIN;
return task_under_cgroup_hierarchy(current, cgrp);
}
static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
.func = bpf_current_task_under_cgroup,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_ANYTHING,
};
static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
case BPF_FUNC_map_lookup_elem:
return &bpf_map_lookup_elem_proto;
case BPF_FUNC_map_update_elem:
return &bpf_map_update_elem_proto;
case BPF_FUNC_map_delete_elem:
return &bpf_map_delete_elem_proto;
case BPF_FUNC_probe_read:
return &bpf_probe_read_proto;
case BPF_FUNC_ktime_get_ns:
return &bpf_ktime_get_ns_proto;
case BPF_FUNC_tail_call:
return &bpf_tail_call_proto;
case BPF_FUNC_get_current_pid_tgid:
return &bpf_get_current_pid_tgid_proto;
case BPF_FUNC_get_current_task:
return &bpf_get_current_task_proto;
case BPF_FUNC_get_current_uid_gid:
return &bpf_get_current_uid_gid_proto;
case BPF_FUNC_get_current_comm:
return &bpf_get_current_comm_proto;
case BPF_FUNC_trace_printk:
return bpf_get_trace_printk_proto();
case BPF_FUNC_get_smp_processor_id:
return &bpf_get_smp_processor_id_proto;
case BPF_FUNC_perf_event_read:
return &bpf_perf_event_read_proto;
case BPF_FUNC_probe_write_user:
return bpf_get_probe_write_proto();
case BPF_FUNC_current_task_under_cgroup:
return &bpf_current_task_under_cgroup_proto;
case BPF_FUNC_get_prandom_u32:
return &bpf_get_prandom_u32_proto;
default:
return NULL;
}
}
static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto;
case BPF_FUNC_get_stackid:
return &bpf_get_stackid_proto;
default:
return tracing_func_proto(func_id);
}
}
/* bpf+kprobe programs can access fields of 'struct pt_regs' */
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
if (off < 0 || off >= sizeof(struct pt_regs))
return false;
if (type != BPF_READ)
return false;
if (off % size != 0)
return false;
return true;
}
static const struct bpf_verifier_ops kprobe_prog_ops = {
.get_func_proto = kprobe_prog_func_proto,
.is_valid_access = kprobe_prog_is_valid_access,
};
static struct bpf_prog_type_list kprobe_tl = {
.ops = &kprobe_prog_ops,
.type = BPF_PROG_TYPE_KPROBE,
};
BPF_CALL_5(bpf_perf_event_output_tp, void *, tp_buff, struct bpf_map *, map,
u64, flags, void *, data, u64, size)
{
struct pt_regs *regs = *(struct pt_regs **)tp_buff;
/*
* r1 points to perf tracepoint buffer where first 8 bytes are hidden
* from bpf program and contain a pointer to 'struct pt_regs'. Fetch it
* from there and call the same bpf_perf_event_output() helper inline.
*/
return ____bpf_perf_event_output(regs, map, flags, data, size);
}
static const struct bpf_func_proto bpf_perf_event_output_proto_tp = {
.func = bpf_perf_event_output_tp,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
.arg4_type = ARG_PTR_TO_STACK,
.arg5_type = ARG_CONST_STACK_SIZE,
};
BPF_CALL_3(bpf_get_stackid_tp, void *, tp_buff, struct bpf_map *, map,
u64, flags)
{
struct pt_regs *regs = *(struct pt_regs **)tp_buff;
/*
* Same comment as in bpf_perf_event_output_tp(), only that this time
* the other helper's function body cannot be inlined due to being
* external, thus we need to call raw helper function.
*/
return bpf_get_stackid((unsigned long) regs, (unsigned long) map,
flags, 0, 0);
}
static const struct bpf_func_proto bpf_get_stackid_proto_tp = {
.func = bpf_get_stackid_tp,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto_tp;
case BPF_FUNC_get_stackid:
return &bpf_get_stackid_proto_tp;
default:
return tracing_func_proto(func_id);
}
}
static bool tp_prog_is_valid_access(int off, int size, enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
if (off < sizeof(void *) || off >= PERF_MAX_TRACE_SIZE)
return false;
if (type != BPF_READ)
return false;
if (off % size != 0)
return false;
return true;
}
static const struct bpf_verifier_ops tracepoint_prog_ops = {
.get_func_proto = tp_prog_func_proto,
.is_valid_access = tp_prog_is_valid_access,
};
static struct bpf_prog_type_list tracepoint_tl = {
.ops = &tracepoint_prog_ops,
.type = BPF_PROG_TYPE_TRACEPOINT,
};
static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
if (off < 0 || off >= sizeof(struct bpf_perf_event_data))
return false;
if (type != BPF_READ)
return false;
if (off % size != 0)
return false;
if (off == offsetof(struct bpf_perf_event_data, sample_period)) {
if (size != sizeof(u64))
return false;
} else {
if (size != sizeof(long))
return false;
}
return true;
}
static u32 pe_prog_convert_ctx_access(enum bpf_access_type type, int dst_reg,
int src_reg, int ctx_off,
struct bpf_insn *insn_buf,
struct bpf_prog *prog)
{
struct bpf_insn *insn = insn_buf;
switch (ctx_off) {
case offsetof(struct bpf_perf_event_data, sample_period):
BUILD_BUG_ON(FIELD_SIZEOF(struct perf_sample_data, period) != sizeof(u64));
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
data), dst_reg, src_reg,
offsetof(struct bpf_perf_event_data_kern, data));
*insn++ = BPF_LDX_MEM(BPF_DW, dst_reg, dst_reg,
offsetof(struct perf_sample_data, period));
break;
default:
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
regs), dst_reg, src_reg,
offsetof(struct bpf_perf_event_data_kern, regs));
*insn++ = BPF_LDX_MEM(BPF_SIZEOF(long), dst_reg, dst_reg, ctx_off);
break;
}
return insn - insn_buf;
}
static const struct bpf_verifier_ops perf_event_prog_ops = {
.get_func_proto = tp_prog_func_proto,
.is_valid_access = pe_prog_is_valid_access,
.convert_ctx_access = pe_prog_convert_ctx_access,
};
static struct bpf_prog_type_list perf_event_tl = {
.ops = &perf_event_prog_ops,
.type = BPF_PROG_TYPE_PERF_EVENT,
};
static int __init register_kprobe_prog_ops(void)
{
bpf_register_prog_type(&kprobe_tl);
bpf_register_prog_type(&tracepoint_tl);
bpf_register_prog_type(&perf_event_tl);
return 0;
}
late_initcall(register_kprobe_prog_ops);