root/arch/powerpc/include/asm/book3s/32/kup.h

INCLUDED FROM

DEFINITIONS

1. KUAP
2. allow_user_access
3. prevent_user_access
4. bad_kuap_fault

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_POWERPC_BOOK3S_32_KUP_H
   3 #define _ASM_POWERPC_BOOK3S_32_KUP_H
   4 
   5 #include <asm/book3s/32/mmu-hash.h>
   6 
   7 #ifdef __ASSEMBLY__
   8 
   9 .macro kuep_update_sr   gpr1, gpr2              /* NEVER use r0 as gpr2 due to addis */
  10 101:    mtsrin  \gpr1, \gpr2
  11         addi    \gpr1, \gpr1, 0x111             /* next VSID */
  12         rlwinm  \gpr1, \gpr1, 0, 0xf0ffffff     /* clear VSID overflow */
  13         addis   \gpr2, \gpr2, 0x1000            /* address of next segment */
  14         bdnz    101b
  15         isync
  16 .endm
  17 
  18 .macro kuep_lock        gpr1, gpr2
  19 #ifdef CONFIG_PPC_KUEP
  20         li      \gpr1, NUM_USER_SEGMENTS
  21         li      \gpr2, 0
  22         mtctr   \gpr1
  23         mfsrin  \gpr1, \gpr2
  24         oris    \gpr1, \gpr1, SR_NX@h           /* set Nx */
  25         kuep_update_sr \gpr1, \gpr2
  26 #endif
  27 .endm
  28 
  29 .macro kuep_unlock      gpr1, gpr2
  30 #ifdef CONFIG_PPC_KUEP
  31         li      \gpr1, NUM_USER_SEGMENTS
  32         li      \gpr2, 0
  33         mtctr   \gpr1
  34         mfsrin  \gpr1, \gpr2
  35         rlwinm  \gpr1, \gpr1, 0, ~SR_NX         /* Clear Nx */
  36         kuep_update_sr \gpr1, \gpr2
  37 #endif
  38 .endm
  39 
  40 #ifdef CONFIG_PPC_KUAP
  41 
  42 .macro kuap_update_sr   gpr1, gpr2, gpr3        /* NEVER use r0 as gpr2 due to addis */
  43 101:    mtsrin  \gpr1, \gpr2
  44         addi    \gpr1, \gpr1, 0x111             /* next VSID */
  45         rlwinm  \gpr1, \gpr1, 0, 0xf0ffffff     /* clear VSID overflow */
  46         addis   \gpr2, \gpr2, 0x1000            /* address of next segment */
  47         cmplw   \gpr2, \gpr3
  48         blt-    101b
  49         isync
  50 .endm
  51 
  52 .macro kuap_save_and_lock       sp, thread, gpr1, gpr2, gpr3
  53         lwz     \gpr2, KUAP(\thread)
  54         rlwinm. \gpr3, \gpr2, 28, 0xf0000000
  55         stw     \gpr2, STACK_REGS_KUAP(\sp)
  56         beq+    102f
  57         li      \gpr1, 0
  58         stw     \gpr1, KUAP(\thread)
  59         mfsrin  \gpr1, \gpr2
  60         oris    \gpr1, \gpr1, SR_KS@h   /* set Ks */
  61         kuap_update_sr  \gpr1, \gpr2, \gpr3
  62 102:
  63 .endm
  64 
  65 .macro kuap_restore     sp, current, gpr1, gpr2, gpr3
  66         lwz     \gpr2, STACK_REGS_KUAP(\sp)
  67         rlwinm. \gpr3, \gpr2, 28, 0xf0000000
  68         stw     \gpr2, THREAD + KUAP(\current)
  69         beq+    102f
  70         mfsrin  \gpr1, \gpr2
  71         rlwinm  \gpr1, \gpr1, 0, ~SR_KS /* Clear Ks */
  72         kuap_update_sr  \gpr1, \gpr2, \gpr3
  73 102:
  74 .endm
  75 
  76 .macro kuap_check       current, gpr
  77 #ifdef CONFIG_PPC_KUAP_DEBUG
  78         lwz     \gpr, KUAP(thread)
  79 999:    twnei   \gpr, 0
  80         EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
  81 #endif
  82 .endm
  83 
  84 #endif /* CONFIG_PPC_KUAP */
  85 
  86 #else /* !__ASSEMBLY__ */
  87 
  88 #ifdef CONFIG_PPC_KUAP
  89 
  90 #include <linux/sched.h>
  91 
  92 static inline void kuap_update_sr(u32 sr, u32 addr, u32 end)
  93 {
  94         addr &= 0xf0000000;     /* align addr to start of segment */
  95         barrier();      /* make sure thread.kuap is updated before playing with SRs */
  96         while (addr < end) {
  97                 mtsrin(sr, addr);
  98                 sr += 0x111;            /* next VSID */
  99                 sr &= 0xf0ffffff;       /* clear VSID overflow */
 100                 addr += 0x10000000;     /* address of next segment */
 101         }
 102         isync();        /* Context sync required after mtsrin() */
 103 }
 104 
 105 static __always_inline void allow_user_access(void __user *to, const void __user *from,
 106                                               u32 size, unsigned long dir)
 107 {
 108         u32 addr, end;
 109 
 110         BUILD_BUG_ON(!__builtin_constant_p(dir));
 111         if (!(dir & KUAP_WRITE))
 112                 return;
 113 
 114         addr = (__force u32)to;
 115 
 116         if (!addr || addr >= TASK_SIZE || !size)
 117                 return;
 118 
 119         end = min(addr + size, TASK_SIZE);
 120         current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
 121         kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end);       /* Clear Ks */
 122 }
 123 
 124 static __always_inline void prevent_user_access(void __user *to, const void __user *from,
 125                                                 u32 size, unsigned long dir)
 126 {
 127         u32 addr = (__force u32)to;
 128         u32 end = min(addr + size, TASK_SIZE);
 129 
 130         BUILD_BUG_ON(!__builtin_constant_p(dir));
 131         if (!(dir & KUAP_WRITE))
 132                 return;
 133 
 134         if (!addr || addr >= TASK_SIZE || !size)
 135                 return;
 136 
 137         current->thread.kuap = 0;
 138         kuap_update_sr(mfsrin(addr) | SR_KS, addr, end);        /* set Ks */
 139 }
 140 
 141 static inline bool
 142 bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 143 {
 144         unsigned long begin = regs->kuap & 0xf0000000;
 145         unsigned long end = regs->kuap << 28;
 146 
 147         if (!is_write)
 148                 return false;
 149 
 150         return WARN(address < begin || address >= end,
 151                     "Bug: write fault blocked by segment registers !");
 152 }
 153 
 154 #endif /* CONFIG_PPC_KUAP */
 155 
 156 #endif /* __ASSEMBLY__ */
 157 
 158 #endif /* _ASM_POWERPC_BOOK3S_32_KUP_H */