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

   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/bug.h>
   6 #include <asm/book3s/32/mmu-hash.h>
   7
   8 #ifdef __ASSEMBLY__
   9
  10 .macro kuep_update_sr   gpr1, gpr2              /* NEVER use r0 as gpr2 due to addis */
  11 101:    mtsrin  \gpr1, \gpr2
  12         addi    \gpr1, \gpr1, 0x111             /* next VSID */
  13         rlwinm  \gpr1, \gpr1, 0, 0xf0ffffff     /* clear VSID overflow */
  14         addis   \gpr2, \gpr2, 0x1000            /* address of next segment */
  15         bdnz    101b
  16         isync
  17 .endm
  18
  19 .macro kuep_lock        gpr1, gpr2
  20 #ifdef CONFIG_PPC_KUEP
  21         li      \gpr1, NUM_USER_SEGMENTS
  22         li      \gpr2, 0
  23         mtctr   \gpr1
  24         mfsrin  \gpr1, \gpr2
  25         oris    \gpr1, \gpr1, SR_NX@h           /* set Nx */
  26         kuep_update_sr \gpr1, \gpr2
  27 #endif
  28 .endm
  29
  30 .macro kuep_unlock      gpr1, gpr2
  31 #ifdef CONFIG_PPC_KUEP
  32         li      \gpr1, NUM_USER_SEGMENTS
  33         li      \gpr2, 0
  34         mtctr   \gpr1
  35         mfsrin  \gpr1, \gpr2
  36         rlwinm  \gpr1, \gpr1, 0, ~SR_NX         /* Clear Nx */
  37         kuep_update_sr \gpr1, \gpr2
  38 #endif
  39 .endm
  40
  41 #ifdef CONFIG_PPC_KUAP
  42
  43 .macro kuap_update_sr   gpr1, gpr2, gpr3        /* NEVER use r0 as gpr2 due to addis */
  44 101:    mtsrin  \gpr1, \gpr2
  45         addi    \gpr1, \gpr1, 0x111             /* next VSID */
  46         rlwinm  \gpr1, \gpr1, 0, 0xf0ffffff     /* clear VSID overflow */
  47         addis   \gpr2, \gpr2, 0x1000            /* address of next segment */
  48         cmplw   \gpr2, \gpr3
  49         blt-    101b
  50         isync
  51 .endm
  52
  53 .macro kuap_save_and_lock       sp, thread, gpr1, gpr2, gpr3
  54         lwz     \gpr2, KUAP(\thread)
  55         rlwinm. \gpr3, \gpr2, 28, 0xf0000000
  56         stw     \gpr2, STACK_REGS_KUAP(\sp)
  57         beq+    102f
  58         li      \gpr1, 0
  59         stw     \gpr1, KUAP(\thread)
  60         mfsrin  \gpr1, \gpr2
  61         oris    \gpr1, \gpr1, SR_KS@h   /* set Ks */
  62         kuap_update_sr  \gpr1, \gpr2, \gpr3
  63 102:
  64 .endm
  65
  66 .macro kuap_restore     sp, current, gpr1, gpr2, gpr3
  67         lwz     \gpr2, STACK_REGS_KUAP(\sp)
  68         rlwinm. \gpr3, \gpr2, 28, 0xf0000000
  69         stw     \gpr2, THREAD + KUAP(\current)
  70         beq+    102f
  71         mfsrin  \gpr1, \gpr2
  72         rlwinm  \gpr1, \gpr1, 0, ~SR_KS /* Clear Ks */
  73         kuap_update_sr  \gpr1, \gpr2, \gpr3
  74 102:
  75 .endm
  76
  77 .macro kuap_check       current, gpr
  78 #ifdef CONFIG_PPC_KUAP_DEBUG
  79         lwz     \gpr, THREAD + KUAP(\current)
  80 999:    twnei   \gpr, 0
  81         EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
  82 #endif
  83 .endm
  84
  85 #endif /* CONFIG_PPC_KUAP */
  86
  87 #else /* !__ASSEMBLY__ */
  88
  89 #ifdef CONFIG_PPC_KUAP
  90
  91 #include <linux/sched.h>
  92
  93 static inline void kuap_update_sr(u32 sr, u32 addr, u32 end)
  94 {
  95         addr &= 0xf0000000;     /* align addr to start of segment */
  96         barrier();      /* make sure thread.kuap is updated before playing with SRs */
  97         while (addr < end) {
  98                 mtsrin(sr, addr);
  99                 sr += 0x111;            /* next VSID */
 100                 sr &= 0xf0ffffff;       /* clear VSID overflow */
 101                 addr += 0x10000000;     /* address of next segment */
 102         }
 103         isync();        /* Context sync required after mtsrin() */
 104 }
 105
 106 static __always_inline void allow_user_access(void __user *to, const void __user *from,
 107                                               u32 size, unsigned long dir)
 108 {
 109         u32 addr, end;
 110
 111         BUILD_BUG_ON(!__builtin_constant_p(dir));
 112         BUILD_BUG_ON(dir & ~KUAP_READ_WRITE);
 113
 114         if (!(dir & KUAP_WRITE))
 115                 return;
 116
 117         addr = (__force u32)to;
 118
 119         if (unlikely(addr >= TASK_SIZE || !size))
 120                 return;
 121
 122         end = min(addr + size, TASK_SIZE);
 123
 124         current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
 125         kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end);       /* Clear Ks */
 126 }
 127
 128 static __always_inline void prevent_user_access(void __user *to, const void __user *from,
 129                                                 u32 size, unsigned long dir)
 130 {
 131         u32 addr, end;
 132
 133         BUILD_BUG_ON(!__builtin_constant_p(dir));
 134
 135         if (dir & KUAP_CURRENT_WRITE) {
 136                 u32 kuap = current->thread.kuap;
 137
 138                 if (unlikely(!kuap))
 139                         return;
 140
 141                 addr = kuap & 0xf0000000;
 142                 end = kuap << 28;
 143         } else if (dir & KUAP_WRITE) {
 144                 addr = (__force u32)to;
 145                 end = min(addr + size, TASK_SIZE);
 146
 147                 if (unlikely(addr >= TASK_SIZE || !size))
 148                         return;
 149         } else {
 150                 return;
 151         }
 152
 153         current->thread.kuap = 0;
 154         kuap_update_sr(mfsrin(addr) | SR_KS, addr, end);        /* set Ks */
 155 }
 156
 157 static inline unsigned long prevent_user_access_return(void)
 158 {
 159         unsigned long flags = current->thread.kuap;
 160         unsigned long addr = flags & 0xf0000000;
 161         unsigned long end = flags << 28;
 162         void __user *to = (__force void __user *)addr;
 163
 164         if (flags)
 165                 prevent_user_access(to, to, end - addr, KUAP_READ_WRITE);
 166
 167         return flags;
 168 }
 169
 170 static inline void restore_user_access(unsigned long flags)
 171 {
 172         unsigned long addr = flags & 0xf0000000;
 173         unsigned long end = flags << 28;
 174         void __user *to = (__force void __user *)addr;
 175
 176         if (flags)
 177                 allow_user_access(to, to, end - addr, KUAP_READ_WRITE);
 178 }
 179
 180 static inline bool
 181 bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 182 {
 183         unsigned long begin = regs->kuap & 0xf0000000;
 184         unsigned long end = regs->kuap << 28;
 185
 186         return is_write && (address < begin || address >= end);
 187 }
 188
 189 #endif /* CONFIG_PPC_KUAP */
 190
 191 #endif /* __ASSEMBLY__ */
 192
 193 #endif /* _ASM_POWERPC_BOOK3S_32_KUP_H */