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7883a14339
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>
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.