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runtime constants: add default dummy infrastructure

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This adds the initial dummy support for 'runtime constants' for when
an architecture doesn't actually support an implementation of fixing
up said runtime constants.

This ends up being the fallback to just using the variables as regular
__ro_after_init variables, and changes the dcache d_hash() function to
use this model.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2024-06-04 12:30:02 -07:00
parent e60cc61153
commit e78298556e
4 changed files with 34 additions and 1 deletions
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11
fs/dcache.c
View File

@ -35,6 +35,8 @@
#include "internal.h"
#include "mount.h"
#include <asm/runtime-const.h>
/*
* Usage:
* dcache->d_inode->i_lock protects:
@ -102,7 +104,8 @@ static struct hlist_bl_head *dentry_hashtable __ro_after_init;
static inline struct hlist_bl_head *d_hash(unsigned long hashlen)
{
return dentry_hashtable + ((u32)hashlen >> d_hash_shift);
return runtime_const_ptr(dentry_hashtable) +
runtime_const_shift_right_32(hashlen, d_hash_shift);
}
#define IN_LOOKUP_SHIFT 10
@ -3129,6 +3132,9 @@ static void __init dcache_init_early(void)
0,
0);
d_hash_shift = 32 - d_hash_shift;
runtime_const_init(shift, d_hash_shift);
runtime_const_init(ptr, dentry_hashtable);
}
static void __init dcache_init(void)
@ -3157,6 +3163,9 @@ static void __init dcache_init(void)
0,
0);
d_hash_shift = 32 - d_hash_shift;
runtime_const_init(shift, d_hash_shift);
runtime_const_init(ptr, dentry_hashtable);
}
/* SLAB cache for __getname() consumers */

1
include/asm-generic/Kbuild
View File

@ -46,6 +46,7 @@ mandatory-y += pci.h
mandatory-y += percpu.h
mandatory-y += pgalloc.h
mandatory-y += preempt.h
mandatory-y += runtime-const.h
mandatory-y += rwonce.h
mandatory-y += sections.h
mandatory-y += serial.h

15
include/asm-generic/runtime-const.h Normal file
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@ -0,0 +1,15 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_RUNTIME_CONST_H
#define _ASM_RUNTIME_CONST_H
/*
* This is the fallback for when the architecture doesn't
* support the runtime const operations.
*
* We just use the actual symbols as-is.
*/
#define runtime_const_ptr(sym) (sym)
#define runtime_const_shift_right_32(val, sym) ((u32)(val)>>(sym))
#define runtime_const_init(type,sym) do { } while (0)
#endif

8
include/asm-generic/vmlinux.lds.h
View File

@ -944,6 +944,14 @@
#define CON_INITCALL \
BOUNDED_SECTION_POST_LABEL(.con_initcall.init, __con_initcall, _start, _end)
#define RUNTIME_NAME(t,x) runtime_##t##_##x
#define RUNTIME_CONST(t,x) \
. = ALIGN(8); \
RUNTIME_NAME(t,x) : AT(ADDR(RUNTIME_NAME(t,x)) - LOAD_OFFSET) { \
*(RUNTIME_NAME(t,x)); \
}
/* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
#define KUNIT_TABLE() \
. = ALIGN(8); \