From: Linus Torvalds torvalds@linux-foundation.org
commit e3c92e81711d14b46c3121d36bc8e152cb843923 upstream.
This implements the runtime constant infrastructure for x86, 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.
Cc: stable@vger.kernel.org # 6.10.x: e60cc61: vfs: dcache: move hashlen_hash Cc: stable@vger.kernel.org # 6.10.x: e782985: runtime constants: add default Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Jimmy Tran jtoantran@google.com --- arch/x86/include/asm/runtime-const.h | 61 ++++++++++++++++++++++++++++ arch/x86/kernel/vmlinux.lds.S | 3 ++ 2 files changed, 64 insertions(+) create mode 100644 arch/x86/include/asm/runtime-const.h
diff --git a/arch/x86/include/asm/runtime-const.h b/arch/x86/include/asm/runtime-const.h new file mode 100644 index 0000000000000..76fdeaa0faa3f --- /dev/null +++ b/arch/x86/include/asm/runtime-const.h @@ -0,0 +1,61 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_RUNTIME_CONST_H +#define _ASM_RUNTIME_CONST_H + +#define runtime_const_ptr(sym) ({ \ + typeof(sym) __ret; \ + asm_inline("mov %1,%0\n1:\n" \ + ".pushsection runtime_ptr_" #sym ","a"\n\t" \ + ".long 1b - %c2 - .\n\t" \ + ".popsection" \ + : "=r" (__ret) \ + : "i" (0x0123456789abcdefULL), \ + "i" (sizeof(long))); \ + __ret; }) + +// The 'typeof' will create at _least_ a 32-bit type, but +// will happily also take a bigger type and the 'shrl' will +// clear the upper bits +#define runtime_const_shift_right_32(val, sym) ({ \ + typeof(0u+(val)) __ret = (val); \ + asm_inline("shrl $12,%k0\n1:\n" \ + ".pushsection runtime_shift_" #sym ","a"\n\t" \ + ".long 1b - 1 - .\n\t" \ + ".popsection" \ + : "+r" (__ret)); \ + __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) + +/* + * The text patching is trivial - you can only do this at init time, + * when the text section hasn't been marked RO, and before the text + * has ever been executed. + */ +static inline void __runtime_fixup_ptr(void *where, unsigned long val) +{ + *(unsigned long *)where = val; +} + +static inline void __runtime_fixup_shift(void *where, unsigned long val) +{ + *(unsigned char *)where = val; +} + +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 diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index c57d5df1abc60..cb5b41480a848 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -371,6 +371,9 @@ SECTIONS PERCPU_SECTION(INTERNODE_CACHE_BYTES) #endif
+ RUNTIME_CONST(shift, d_hash_shift) + RUNTIME_CONST(ptr, dentry_hashtable) + . = ALIGN(PAGE_SIZE);
/* freed after init ends here */