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Inspired by x86 commit 864b435514b2("x86/jump_label: Mark arguments as
const to satisfy asm constraints"), constify alternative_has_feature_*
argument to satisfy asm constraints. And Steven in [1] also pointed
out that "The "i" constraint needs to be a constant."
Tested with building a simple external kernel module with "O0".
Before the patch, got similar gcc warnings and errors as below:
In file included from <command-line>:
In function ‘alternative_has_feature_likely’,
inlined from ‘system_capabilities_finalized’ at
arch/arm64/include/asm/cpufeature.h:440:9,
inlined from ‘arm64_preempt_schedule_irq’ at
arch/arm64/kernel/entry-common.c:264:6:
include/linux/compiler_types.h:285:33: warning:
‘asm’ operand 0 probably does not match constraints
285 | #define asm_volatile_goto(x...) asm goto(x)
| ^~~
arch/arm64/include/asm/alternative-macros.h:232:9:
note: in expansion of macro ‘asm_volatile_goto’
232 | asm_volatile_goto(
| ^~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:285:33: error:
impossible constraint in ‘asm’
285 | #define asm_volatile_goto(x...) asm goto(x)
| ^~~
arch/arm64/include/asm/alternative-macros.h:232:9:
note: in expansion of macro ‘asm_volatile_goto’
232 | asm_volatile_goto(
| ^~~~~~~~~~~~~~~~~
After the patch, the simple external test kernel module is built fine
with "-O0".
[1]https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20221006075542.2658-3-jszhang@kernel.org
Signed-off-by: Will Deacon <will@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.