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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.