arch/mips/vdso/vdso.h

   1 /*
   2  * Copyright (C) 2015 Imagination Technologies
   3  * Author: Alex Smith <alex.smith@imgtec.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation;  either version 2 of the  License, or (at your
   8  * option) any later version.
   9  */
  10
  11 #include <asm/sgidefs.h>
  12
  13 #if _MIPS_SIM != _MIPS_SIM_ABI64 && defined(CONFIG_64BIT)
  14
  15 /* Building 32-bit VDSO for the 64-bit kernel. Fake a 32-bit Kconfig. */
  16 #undef CONFIG_64BIT
  17 #define CONFIG_32BIT 1
  18 #ifndef __ASSEMBLY__
  19 #include <asm-generic/atomic64.h>
  20 #endif
  21 #endif
  22
  23 #ifndef __ASSEMBLY__
  24
  25 #include <asm/asm.h>
  26 #include <asm/page.h>
  27 #include <asm/vdso.h>
  28
  29 static inline unsigned long get_vdso_base(void)
  30 {
  31         unsigned long addr;
  32
  33         /*
  34          * We can't use cpu_has_mips_r6 since it needs the cpu_data[]
  35          * kernel symbol.
  36          */
  37 #ifdef CONFIG_CPU_MIPSR6
  38         /*
  39          * lapc <symbol> is an alias to addiupc reg, <symbol> - .
  40          *
  41          * We can't use addiupc because there is no label-label
  42          * support for the addiupc reloc
  43          */
  44         __asm__("lapc   %0, _start                      \n"
  45                 : "=r" (addr) : :);
  46 #else
  47         /*
  48          * Get the base load address of the VDSO. We have to avoid generating
  49          * relocations and references to the GOT because ld.so does not peform
  50          * relocations on the VDSO. We use the current offset from the VDSO base
  51          * and perform a PC-relative branch which gives the absolute address in
  52          * ra, and take the difference. The assembler chokes on
  53          * "li %0, _start - .", so embed the offset as a word and branch over
  54          * it.
  55          *
  56          */
  57
  58         __asm__(
  59         "       .set push                               \n"
  60         "       .set noreorder                          \n"
  61         "       bal     1f                              \n"
  62         "        nop                                    \n"
  63         "       .word   _start - .                      \n"
  64         "1:     lw      %0, 0($31)                      \n"
  65         "       " STR(PTR_ADDU) " %0, $31, %0           \n"
  66         "       .set pop                                \n"
  67         : "=r" (addr)
  68         :
  69         : "$31");
  70 #endif /* CONFIG_CPU_MIPSR6 */
  71
  72         return addr;
  73 }
  74
  75 static inline const union mips_vdso_data *get_vdso_data(void)
  76 {
  77         return (const union mips_vdso_data *)(get_vdso_base() - PAGE_SIZE);
  78 }
  79
  80 #ifdef CONFIG_CLKSRC_MIPS_GIC
  81
  82 static inline void __iomem *get_gic(const union mips_vdso_data *data)
  83 {
  84         return (void __iomem *)data - PAGE_SIZE;
  85 }
  86
  87 #endif /* CONFIG_CLKSRC_MIPS_GIC */
  88
  89 #endif /* __ASSEMBLY__ */