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Athira Rajeev 557c3eadb7 perf powerpc: Fix gap between kernel end and module start
Running "perf mem report" in TUI mode fails with ENOMEM message in
powerpc:

  failed to process sample

Running with debug and verbose options points that issue is while
allocating memory for sample histograms.

The error path is:

  symbol__inc_addr_samples() ->
    __symbol__inc_addr_samples() ->
      annotated_source__histogram()

symbol__inc_addr_samples() calls annotated_source__alloc_histograms ()
to allocate memory for sample histograms using calloc(). Here calloc()
fails since the size of symbol is huge. The size of a symbol is
calculated as difference between its start and end address.

Example histogram allocation that fails is:

  sym->name is _end
  sym->start is 0xc0000000027a0000
  sym->end is 0xc008000003890000
  symbol__size(sym) is 0x80000010f0000

In the above case, the difference between sym->start
(0xc0000000027a0000) and sym->end (0xc008000003890000) is huge.

This is same problem as in s390 and arm64 which are fixed in commits:

  b9c0a64901 ("perf annotate: Fix s390 gap between kernel end and module start")
  78886f3ed3 ("perf symbols: Fix arm64 gap between kernel start and module end")

When this symbol was read first, its start and end address was set to
address which matches with data from /proc/kallsyms.

After symbol__new():

  symbol__new: _end 0xc0000000027a0000-0xc0000000027a0000

  From /proc/kallsyms:
  ...
  c000000002799370 b backtrace_flag
  c000000002799378 B radix_tree_node_cachep
  c000000002799380 B __bss_stop
  c0000000027a0000 B _end
  c008000003890000 t icmp_checkentry      [ip_tables]
  c008000003890038 t ipt_alloc_initial_table      [ip_tables]
  c008000003890468 T ipt_do_table [ip_tables]
  c008000003890de8 T ipt_unregister_table_pre_exit        [ip_tables]
  ...

Perf calls function symbols__fixup_end() which sets the end of symbol to
0xc008000003890000, which is the next address and this is the start
address of first module (icmp_checkentry in above) which will make the
huge symbol size of 0x80000010f0000.

After symbols__fixup_end:

  symbols__fixup_end: sym->name: _end
  sym->start: 0xc0000000027a0000
  sym->end: 0xc008000003890000

On powerpc, kernel text segment is located at 0xc000000000000000 whereas
the modules are located at very high memory addresses,
0xc00800000xxxxxxx. Since the gap between end of kernel text segment and
beginning of first module's address is high, histogram allocation using
calloc fails.

Fix this by detecting the kernel's last symbol and limiting the range of
last kernel symbol to pagesize.

Signed-off-by: Athira Rajeev<atrajeev@linux.vnet.ibm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-By: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1609208054-1566-1-git-send-email-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2021-02-03 13:10:44 -03:00
Documentation * x86 bugfixes 2021-01-26 11:10:14 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
arch Merge branch 'parisc-5.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2021-01-27 11:06:15 -08:00
block block-5.11-2021-01-10 2021-01-10 12:53:08 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto X.509: Fix crash caused by NULL pointer 2021-01-20 11:33:51 -08:00
drivers spi: Fixes for v5.11 2021-01-26 11:03:30 -08:00
fs fs/pipe: allow sendfile() to pipe again 2021-01-25 12:32:26 -08:00
include regulator: Fixes for v5.11 2021-01-26 10:59:01 -08:00
init Revert "init/console: Use ttynull as a fallback when there is no console" 2021-01-08 11:02:18 -08:00
ipc Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
kernel Printk urgent fixup for 5.11-rc6 2021-01-25 10:19:40 -08:00
lib ubsan: disable unsigned-overflow check for i386 2021-01-24 10:34:52 -08:00
mm Revert "mm: fix initialization of struct page for holes in memory layout" 2021-01-26 10:39:46 -08:00
net A patch to zero out sensitive cryptographic data and two minor cleanups 2021-01-22 13:47:25 -08:00
samples ARM: SoC drivers for v5.11 2020-12-16 16:38:41 -08:00
scripts Kbuild fixes for v5.11 2021-01-10 13:24:55 -08:00
security dump_common_audit_data(): fix racy accesses to ->d_name 2021-01-16 15:11:35 -05:00
sound ALSA: usb-audio: Fix hw constraints dependencies 2021-01-20 21:46:45 +01:00
tools perf powerpc: Fix gap between kernel end and module start 2021-02-03 13:10:44 -03:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM/arm64 fixes for 5.11, take #2 2021-01-25 18:52:01 -05:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: remove the "repo-abbrev" comment 2021-01-26 11:40:17 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: dccp: move Gerrit Renker to CREDITS 2021-01-14 10:53:49 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2021-01-24 12:16:34 -08:00
Makefile Linux 5.11-rc5 2021-01-24 16:47:14 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.