arch/mips/include/asm/vdso/vdso.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Copyright (C) 2015 Imagination Technologies
   4  * Author: Alex Smith <alex.smith@imgtec.com>
   5  */
   6
   7 #include <asm/sgidefs.h>
   8
   9 #ifndef __ASSEMBLY__
  10
  11 #include <asm/asm.h>
  12 #include <asm/page.h>
  13 #include <asm/vdso.h>
  14
  15 static inline unsigned long get_vdso_base(void)
  16 {
  17         unsigned long addr;
  18
  19         /*
  20          * We can't use cpu_has_mips_r6 since it needs the cpu_data[]
  21          * kernel symbol.
  22          */
  23 #ifdef CONFIG_CPU_MIPSR6
  24         /*
  25          * lapc <symbol> is an alias to addiupc reg, <symbol> - .
  26          *
  27          * We can't use addiupc because there is no label-label
  28          * support for the addiupc reloc
  29          */
  30         __asm__("lapc   %0, _start                      \n"
  31                 : "=r" (addr) : :);
  32 #else
  33         /*
  34          * Get the base load address of the VDSO. We have to avoid generating
  35          * relocations and references to the GOT because ld.so does not peform
  36          * relocations on the VDSO. We use the current offset from the VDSO base
  37          * and perform a PC-relative branch which gives the absolute address in
  38          * ra, and take the difference. The assembler chokes on
  39          * "li %0, _start - .", so embed the offset as a word and branch over
  40          * it.
  41          *
  42          */
  43
  44         __asm__(
  45         "       .set push                               \n"
  46         "       .set noreorder                          \n"
  47         "       bal     1f                              \n"
  48         "        nop                                    \n"
  49         "       .word   _start - .                      \n"
  50         "1:     lw      %0, 0($31)                      \n"
  51         "       " STR(PTR_ADDU) " %0, $31, %0           \n"
  52         "       .set pop                                \n"
  53         : "=r" (addr)
  54         :
  55         : "$31");
  56 #endif /* CONFIG_CPU_MIPSR6 */
  57
  58         return addr;
  59 }
  60
  61 static inline const struct vdso_data *get_vdso_data(void)
  62 {
  63         return (const struct vdso_data *)(get_vdso_base() - PAGE_SIZE);
  64 }
  65
  66 #ifdef CONFIG_CLKSRC_MIPS_GIC
  67
  68 static inline void __iomem *get_gic(const struct vdso_data *data)
  69 {
  70         return (void __iomem *)data - PAGE_SIZE;
  71 }
  72
  73 #endif /* CONFIG_CLKSRC_MIPS_GIC */
  74
  75 #endif /* __ASSEMBLY__ */