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Masahiro Yamada d32b55f4bb kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols

Every EXPORT_SYMBOL creates __kstrtab_* and __kstrtabns_*, which
consumes 15-20% of the kallsyms entries.

For example, on the system built from the x86_64 defconfig,

  $ cat /proc/kallsyms | wc
     129527    388581   5685465
  $ cat /proc/kallsyms | grep __kstrtab | wc
      23489     70467   1187932

We already ignore __crc_* symbols populated by EXPORT_SYMBOL, so it
should be fine to ignore __kstrtab_* and __kstrtabns_* as well.

This makes vmlinux a bit smaller.

  $ size vmlinux.before vmlinux.after
     text    data     bss     dec     hex filename
  22785374        8559694 1413328 32758396        1f3da7c vmlinux.before
  22785374        8137806 1413328 32336508        1ed6a7c vmlinux.after

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

2022-10-03 03:51:58 +09:00

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#!/bin/sh -x

Based on the vmlinux file create the System.map file

System.map is used by module-init tools and some debugging

tools to retrieve the actual addresses of symbols in the kernel.

Usage

mksysmap vmlinux System.map

Generate System.map (actual filename passed as second argument)

$NM produces the following output:

f0081e80 T alloc_vfsmnt

The second row specify the type of the symbol:

A = Absolute

B = Uninitialised data (.bss)

C = Common symbol

D = Initialised data

G = Initialised data for small objects

I = Indirect reference to another symbol

N = Debugging symbol

R = Read only

S = Uninitialised data for small objects

T = Text code symbol

U = Undefined symbol

V = Weak symbol

W = Weak symbol

Corresponding small letters are local symbols

For System.map filter away:

a - local absolute symbols

U - undefined global symbols

N - debugging symbols

w - local weak symbols

readprofile starts reading symbols when _stext is found, and

continue until it finds a symbol which is not either of 'T', 't',

'W' or 'w'.

Ignored prefixes:

$ - local symbols for ARM, MIPS, etc.

.L - local labels, .LBB,.Ltmpxxx,.L__unnamed_xx,.LASANPC, etc.

_crc - modversions

_kstrtab - EXPORT_SYMBOL (symbol name)

_kstrtabns - EXPORT_SYMBOL (namespace)

Ignored symbols:

L0 - for LoongArch?

$NM -n $1 | grep -v
-e ' [aNUw] '
-e ' $'
-e ' .L'
-e ' _crc'
-e ' _kstrtab'
-e ' _kstrtabns'
-e ' L0$' \

$2

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