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77dc55a978
When building a 64-bit kernel on a 32-bit build host, incorrect
input MODULE_ALIAS() entries may be generated.
For example, when compiling a 64-bit kernel with CONFIG_INPUT_MOUSEDEV=m
on a 64-bit build machine, you will get the correct output:
$ grep MODULE_ALIAS drivers/input/mousedev.mod.c
MODULE_ALIAS("input:b*v*p*e*-e*1,*2,*k*110,*r*0,*1,*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*2,*k*r*8,*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*14A,*r*a*0,*1,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*145,*r*a*0,*1,*18,*1C,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*110,*r*a*0,*1,*m*l*s*f*w*");
However, building the same kernel on a 32-bit machine results in
incorrect output:
$ grep MODULE_ALIAS drivers/input/mousedev.mod.c
MODULE_ALIAS("input:b*v*p*e*-e*1,*2,*k*110,*130,*r*0,*1,*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*2,*k*r*8,*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*14A,*16A,*r*a*0,*1,*20,*21,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*145,*165,*r*a*0,*1,*18,*1C,*20,*21,*38,*3C,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*3,*k*110,*130,*r*a*0,*1,*20,*21,*m*l*s*f*w*");
A similar issue occurs with CONFIG_INPUT_JOYDEV=m. On a 64-bit build
machine, the output is:
$ grep MODULE_ALIAS drivers/input/joydev.mod.c
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*0,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*2,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*8,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*6,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*120,*r*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*130,*r*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*2C0,*r*a*m*l*s*f*w*");
However, on a 32-bit machine, the output is incorrect:
$ grep MODULE_ALIAS drivers/input/joydev.mod.c
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*0,*20,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*2,*22,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*8,*28,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*3,*k*r*a*6,*26,*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*11F,*13F,*r*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*11F,*13F,*r*a*m*l*s*f*w*");
MODULE_ALIAS("input:b*v*p*e*-e*1,*k*2C0,*2E0,*r*a*m*l*s*f*w*");
When building a 64-bit kernel, BITS_PER_LONG is defined as 64. However,
on a 32-bit build machine, the constant 1L is a signed 32-bit value.
Left-shifting it beyond 32 bits causes wraparound, and shifting by 31
or 63 bits makes it a negative value.
The fix in commit e0e9263271 ("[PATCH] PATCH: 1 line 2.6.18 bugfix:
modpost-64bit-fix.patch") is incorrect; it only addresses cases where
a 64-bit kernel is built on a 64-bit build machine, overlooking cases
on a 32-bit build machine.
Using 1ULL ensures a 64-bit width on both 32-bit and 64-bit machines,
avoiding the wraparound issue.
Fixes: e0e9263271 ("[PATCH] PATCH: 1 line 2.6.18 bugfix: modpost-64bit-fix.patch")
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 reStructuredText 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.