41ca1d1e88
When run as normal user with default sysctl kernel.kptr_restrict=0 and kernel.perf_event_paranoid=2, perf probe fails with: $ ./perf probe move_page_tables Relocated base symbol is not found! The warning message is not much informative. The reason perf fails is because /proc/kallsyms is restricted by perf_event_paranoid=2 for normal user and thus perf fails to read relocated address of the base symbol. Tweaking kptr_restrict and perf_event_paranoid can change the behavior of perf probe. Also, running as root or privileged user works too. Add these details in the warning message. Plus, kmap->ref_reloc_sym might not be always set even if host_machine is initialized. Above is the example of the same. Remove that comment. Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Link: http://lore.kernel.org/lkml/20210525043744.193297-1-ravi.bangoria@linux.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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.
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.