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Mikhail Petrov 7883a14339 scripts/kallsyms: fix wrong kallsyms_relative_base
There is the code in the read_symbol function in 'scripts/kallsyms.c':

	if (is_ignored_symbol(name, type))
		return NULL;

	/* Ignore most absolute/undefined (?) symbols. */
	if (strcmp(name, "_text") == 0)
		_text = addr;

But the is_ignored_symbol function returns true for name="_text" and
type='A'. So the next condition is not executed and the _text variable
is always zero.

It makes the wrong kallsyms_relative_base symbol as a result of the code
(CONFIG_KALLSYMS_BASE_RELATIVE is defined):

	if (base_relative) {
		output_label("kallsyms_relative_base");
		output_address(relative_base);
		printf("\n");
	}

Because the output_address function uses the _text variable.

So the kallsyms_lookup function and all related functions in the kernel
do not work properly. For example, the stack trace in oops:

 Call Trace:
 [aa095e58] [809feab8] kobj_ns_ops_tbl+0x7ff09ac8/0x7ff1c1c4 (unreliable)
 [aa095e98] [80002b64] kobj_ns_ops_tbl+0x7f50db74/0x80000010
 [aa095ef8] [809c3d24] kobj_ns_ops_tbl+0x7feced34/0x7ff1c1c4
 [aa095f28] [80002ed0] kobj_ns_ops_tbl+0x7f50dee0/0x80000010
 [aa095f38] [8000f238] kobj_ns_ops_tbl+0x7f51a248/0x80000010

The right stack trace:

 Call Trace:
 [aa095e58] [809feab8] module_vdu_video_init+0x2fc/0x3bc (unreliable)
 [aa095e98] [80002b64] do_one_initcall+0x40/0x1f0
 [aa095ef8] [809c3d24] kernel_init_freeable+0x164/0x1d8
 [aa095f28] [80002ed0] kernel_init+0x14/0x124
 [aa095f38] [8000f238] ret_from_kernel_thread+0x14/0x1c

[masahiroy@kernel.org:

This issue happens on binutils <= 2.22
The following commit fixed it:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d2667025dd30611514810c28bee9709e4623012a

The symbol type of _text is 'T' on binutils >= 2.23
The minimal supported binutils version for the kernel build is 2.21
]

Signed-off-by: Mikhail Petrov <Mikhail.Petrov@mir.dev>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-03-19 23:40:20 +09:00
arch More bugfixes, including a few remaining "make W=1" issues such 2020-03-01 15:16:35 -06:00
block blk-mq: Remove some unused function arguments 2020-02-26 10:34:41 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
Documentation modpost: move the namespace field in Module.symvers last 2020-03-17 08:59:03 +09:00
drivers Merge branch 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2020-02-29 19:16:46 -06:00
fs Two more bug fixes (including a regression) for 5.6 2020-03-01 16:35:08 -06:00
include More bugfixes, including a few remaining "make W=1" issues such 2020-03-01 15:16:35 -06:00
init int128: fix __uint128_t compiler test in Kconfig 2020-03-12 07:43:03 +09:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-21 11:22:15 -08:00
kernel block-5.6-2020-02-28 2020-02-28 11:43:30 -08:00
lib Tracing updates: 2020-02-26 10:34:42 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-24 11:32:15 -08:00
net vsock: fix potential deadlock in transport->release() 2020-02-27 12:03:56 -08:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts scripts/kallsyms: fix wrong kallsyms_relative_base 2020-03-19 23:40:20 +09:00
security Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
sound ASoC: Fixes for v5.6 2020-02-18 13:33:39 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-02-27 16:34:41 -08:00
usr initramfs: restore default compression behavior 2020-03-17 09:50:37 +09:00
virt KVM/arm fixes for 5.6, take #1 2020-02-28 11:50:06 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.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 selftest/lkdtm: Don't pollute 'git status' 2020-02-20 08:55:06 -07:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS pci-v5.6-fixes-2 2020-02-28 11:51:53 -08:00
Makefile kbuild: Fix inconsistent comment 2020-03-12 07:39:30 +09:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.