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arm64: add 'runtime constant' support

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This implements the runtime constant infrastructure for arm64, allowing
the dcache d_hash() function to be generated using as a constant for
hash table address followed by shift by a constant of the hash index.

[ Fixed up to deal with the big-endian case as per Mark Rutland ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2024-06-08 13:22:31 -07:00
parent e3c92e8171
commit 94a2bc0f61
2 changed files with 91 additions and 0 deletions
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88
arch/arm64/include/asm/runtime-const.h Normal file
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@ -0,0 +1,88 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_RUNTIME_CONST_H
#define _ASM_RUNTIME_CONST_H
#include <asm/cacheflush.h>
/* Sigh. You can still run arm64 in BE mode */
#include <asm/byteorder.h>
#define runtime_const_ptr(sym) ({ \
typeof(sym) __ret; \
asm_inline("1:\t" \
"movz %0, #0xcdef\n\t" \
"movk %0, #0x89ab, lsl #16\n\t" \
"movk %0, #0x4567, lsl #32\n\t" \
"movk %0, #0x0123, lsl #48\n\t" \
".pushsection runtime_ptr_" #sym ",\"a\"\n\t" \
".long 1b - .\n\t" \
".popsection" \
:"=r" (__ret)); \
__ret; })
#define runtime_const_shift_right_32(val, sym) ({ \
unsigned long __ret; \
asm_inline("1:\t" \
"lsr %w0,%w1,#12\n\t" \
".pushsection runtime_shift_" #sym ",\"a\"\n\t" \
".long 1b - .\n\t" \
".popsection" \
:"=r" (__ret) \
:"r" (0u+(val))); \
__ret; })
#define runtime_const_init(type, sym) do { \
extern s32 __start_runtime_##type##_##sym[]; \
extern s32 __stop_runtime_##type##_##sym[]; \
runtime_const_fixup(__runtime_fixup_##type, \
(unsigned long)(sym), \
__start_runtime_##type##_##sym, \
__stop_runtime_##type##_##sym); \
} while (0)
/* 16-bit immediate for wide move (movz and movk) in bits 5..20 */
static inline void __runtime_fixup_16(__le32 *p, unsigned int val)
{
u32 insn = le32_to_cpu(*p);
insn &= 0xffe0001f;
insn |= (val & 0xffff) << 5;
*p = cpu_to_le32(insn);
}
static inline void __runtime_fixup_caches(void *where, unsigned int insns)
{
unsigned long va = (unsigned long)where;
caches_clean_inval_pou(va, va + 4*insns);
}
static inline void __runtime_fixup_ptr(void *where, unsigned long val)
{
__le32 *p = lm_alias(where);
__runtime_fixup_16(p, val);
__runtime_fixup_16(p+1, val >> 16);
__runtime_fixup_16(p+2, val >> 32);
__runtime_fixup_16(p+3, val >> 48);
__runtime_fixup_caches(where, 4);
}
/* Immediate value is 6 bits starting at bit #16 */
static inline void __runtime_fixup_shift(void *where, unsigned long val)
{
__le32 *p = lm_alias(where);
u32 insn = le32_to_cpu(*p);
insn &= 0xffc0ffff;
insn |= (val & 63) << 16;
*p = cpu_to_le32(insn);
__runtime_fixup_caches(where, 1);
}
static inline void runtime_const_fixup(void (*fn)(void *, unsigned long),
unsigned long val, s32 *start, s32 *end)
{
while (start < end) {
fn(*start + (void *)start, val);
start++;
}
}
#endif

3
arch/arm64/kernel/vmlinux.lds.S
View file

@ -264,6 +264,9 @@ SECTIONS
EXIT_DATA
}
RUNTIME_CONST(shift, d_hash_shift)
RUNTIME_CONST(ptr, dentry_hashtable)
PERCPU_SECTION(L1_CACHE_BYTES)
HYPERVISOR_PERCPU_SECTION