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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>