Merge branch 'bpf_get_stack'

Yonghong Song says:

====================
Currently, stackmap and bpf_get_stackid helper are provided
for bpf program to get the stack trace. This approach has
a limitation though. If two stack traces have the same hash,
only one will get stored in the stackmap table regardless of
whether BPF_F_REUSE_STACKID is specified or not,
so some stack traces may be missing from user perspective.

This patch implements a new helper, bpf_get_stack, will
send stack traces directly to bpf program. The bpf program
is able to see all stack traces, and then can do in-kernel
processing or send stack traces to user space through
shared map or bpf_perf_event_output.

Patches #1 and #2 implemented the core kernel support.
Patch #3 removes two never-hit branches in verifier.
Patches #4 and #5 are two verifier improves to make
bpf programming easier. Patch #6 synced the new helper
to tools headers. Patch #7 moved perf_event polling code
and ksym lookup code from samples/bpf to
tools/testing/selftests/bpf. Patch #8 added a verifier
test in tools/bpf for new verifier change.
Patches #9 and #10 added tests for raw tracepoint prog
and tracepoint prog respectively.

Changelogs:
  v8 -> v9:
    . make function perf_event_mmap (in trace_helpers.c) extern
      to decouple perf_event_mmap and perf_event_poller.
    . add jit enabled handling for kernel stack verification
      in Patch #9. Since we did not have a good way to
      verify jit enabled kernel stack, just return true if
      the kernel stack is not empty.
    . In path #9, using raw_syscalls/sys_enter instead of
      sched/sched_switch, removed calling cmd
      "task 1 dd if=/dev/zero of=/dev/null" which is left
      with dangling process after the program exited.
  v7 -> v8:
    . rebase on top of latest bpf-next
    . simplify BPF_ARSH dst_reg->smin_val/smax_value tracking
    . rewrite the description of bpf_get_stack() in uapi bpf.h
      based on new format.
  v6 -> v7:
    . do perf callchain buffer allocation inside the
      verifier. so if the prog->has_callchain_buf is set,
      it is guaranteed that the buffer has been allocated.
    . change condition "trace_nr <= skip" to "trace_nr < skip"
      so that for zero size buffer, return 0 instead of -EFAULT
  v5 -> v6:
    . after refining return register smax_value and umax_value
      for helpers bpf_get_stack and bpf_probe_read_str,
      bounds and var_off of the return register are further refined.
    . added missing commit message for tools header sync commit.
    . removed one unnecessary empty line.
  v4 -> v5:
    . relied on dst_reg->var_off to refine umin_val/umax_val
      in verifier handling BPF_ARSH value range tracking,
      suggested by Edward.
  v3 -> v4:
    . fixed a bug when meta ptr is set to NULL in check_func_arg.
    . introduced tnum_arshift and added detailed comments for
      the underlying implementation
    . avoided using VLA in tools/bpf test_progs.
  v2 -> v3:
    . used meta to track helper memory size argument
    . implemented range checking for ARSH in verifier
    . moved perf event polling and ksym related functions
      from samples/bpf to tools/bpf
    . added test to compare build id's between bpf_get_stackid
      and bpf_get_stack
  v1 -> v2:
    . fixed compilation error when CONFIG_PERF_EVENTS is not enabled
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 38ebbc61ed99..c553f6f9c6b0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -692,6 +692,7 @@ extern const struct bpf_func_proto bpf_get_current_comm_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
 extern const struct bpf_func_proto bpf_get_stackid_proto;
+extern const struct bpf_func_proto bpf_get_stack_proto;
 extern const struct bpf_func_proto bpf_sock_map_update_proto;
 
 /* Shared helpers among cBPF and eBPF. */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 4da8b2308174..64899c04c1a6 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -468,7 +468,8 @@ struct bpf_prog {
 				dst_needed:1,	/* Do we need dst entry? */
 				blinded:1,	/* Was blinded */
 				is_func:1,	/* program is a bpf function */
-				kprobe_override:1; /* Do we override a kprobe? */
+				kprobe_override:1, /* Do we override a kprobe? */
+				has_callchain_buf:1; /* callchain buffer allocated? */
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	enum bpf_attach_type	expected_attach_type; /* For some prog types */
 	u32			len;		/* Number of filter blocks */
diff --git a/include/linux/tnum.h b/include/linux/tnum.h
index 0d2d3da46139..c7dc2b5902c0 100644
--- a/include/linux/tnum.h
+++ b/include/linux/tnum.h
@@ -23,8 +23,10 @@ struct tnum tnum_range(u64 min, u64 max);
 /* Arithmetic and logical ops */
 /* Shift a tnum left (by a fixed shift) */
 struct tnum tnum_lshift(struct tnum a, u8 shift);
-/* Shift a tnum right (by a fixed shift) */
+/* Shift (rsh) a tnum right (by a fixed shift) */
 struct tnum tnum_rshift(struct tnum a, u8 shift);
+/* Shift (arsh) a tnum right (by a fixed min_shift) */
+struct tnum tnum_arshift(struct tnum a, u8 min_shift);
 /* Add two tnums, return @a + @b */
 struct tnum tnum_add(struct tnum a, struct tnum b);
 /* Subtract two tnums, return @a - @b */