s390: Add runtime constant support

Implement the runtime constant infrastructure for s390, 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.

This is the s390 variant of commit 94a2bc0f611c ("arm64: add 'runtime
constant' support") and commit e3c92e81711d ("runtime constants: add
x86 architecture support").

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/include/asm/runtime-const.h b/arch/s390/include/asm/runtime-const.h
new file mode 100644 (file)
index 0000000..17878b1
--- /dev/null
+++ b/arch/s390/include/asm/runtime-const.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_RUNTIME_CONST_H
+#define _ASM_S390_RUNTIME_CONST_H
+
+#include <linux/uaccess.h>
+
+#define runtime_const_ptr(sym)                                 \
+({                                                             \
+       typeof(sym) __ret;                                      \
+                                                               \
+       asm_inline(                                             \
+               "0:     iihf    %[__ret],%[c1]\n"               \
+               "       iilf    %[__ret],%[c2]\n"               \
+               ".pushsection runtime_ptr_" #sym ",\"a\"\n"     \
+               ".long 0b - .\n"                                \
+               ".popsection"                                   \
+               : [__ret] "=d" (__ret)                          \
+               : [c1] "i" (0x01234567UL),                      \
+                 [c2] "i" (0x89abcdefUL));                     \
+       __ret;                                                  \
+})
+
+#define runtime_const_shift_right_32(val, sym)                 \
+({                                                             \
+       unsigned int __ret = (val);                             \
+                                                               \
+       asm_inline(                                             \
+               "0:     srl     %[__ret],12\n"                  \
+               ".pushsection runtime_shift_" #sym ",\"a\"\n"   \
+               ".long 0b - .\n"                                \
+               ".popsection"                                   \
+               : [__ret] "+d" (__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)
+
+/* 32-bit immediate for iihf and iilf in bits in I2 field */
+static inline void __runtime_fixup_32(u32 *p, unsigned int val)
+{
+       s390_kernel_write(p, &val, sizeof(val));
+}
+
+static inline void __runtime_fixup_ptr(void *where, unsigned long val)
+{
+       __runtime_fixup_32(where + 2, val >> 32);
+       __runtime_fixup_32(where + 8, val);
+}
+
+/* Immediate value is lower 12 bits of D2 field of srl */
+static inline void __runtime_fixup_shift(void *where, unsigned long val)
+{
+       u32 insn = *(u32 *)where;
+
+       insn &= 0xfffff000;
+       insn |= (val & 63);
+       s390_kernel_write(where, &insn, sizeof(insn));
+}
+
+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 /* _ASM_S390_RUNTIME_CONST_H */

diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index a1ce3925ec719055d14dfbeb8e5eb63416bc2d31..5128ccee9c6746289ea055485c8bf2038f2716a1 100644 (file)
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -190,6 +190,9 @@ SECTIONS
        . = ALIGN(PAGE_SIZE);
        INIT_DATA_SECTION(0x100)
 
+       RUNTIME_CONST(shift, d_hash_shift)
+       RUNTIME_CONST(ptr, dentry_hashtable)
+
        PERCPU_SECTION(0x100)
 
        . = ALIGN(PAGE_SIZE);