root/arch/powerpc/include/asm/book3s/64/kup-radix.h

INCLUDED FROM

DEFINITIONS

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

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H
   3 #define _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H
   4 
   5 #include <linux/const.h>
   6 
   7 #define AMR_KUAP_BLOCK_READ     UL(0x4000000000000000)
   8 #define AMR_KUAP_BLOCK_WRITE    UL(0x8000000000000000)
   9 #define AMR_KUAP_BLOCKED        (AMR_KUAP_BLOCK_READ | AMR_KUAP_BLOCK_WRITE)
  10 #define AMR_KUAP_SHIFT          62
  11 
  12 #ifdef __ASSEMBLY__
  13 
  14 .macro kuap_restore_amr gpr
  15 #ifdef CONFIG_PPC_KUAP
  16         BEGIN_MMU_FTR_SECTION_NESTED(67)
  17         ld      \gpr, STACK_REGS_KUAP(r1)
  18         mtspr   SPRN_AMR, \gpr
  19         END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_RADIX_KUAP, 67)
  20 #endif
  21 .endm
  22 
  23 .macro kuap_check_amr gpr1, gpr2
  24 #ifdef CONFIG_PPC_KUAP_DEBUG
  25         BEGIN_MMU_FTR_SECTION_NESTED(67)
  26         mfspr   \gpr1, SPRN_AMR
  27         li      \gpr2, (AMR_KUAP_BLOCKED >> AMR_KUAP_SHIFT)
  28         sldi    \gpr2, \gpr2, AMR_KUAP_SHIFT
  29 999:    tdne    \gpr1, \gpr2
  30         EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
  31         END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_RADIX_KUAP, 67)
  32 #endif
  33 .endm
  34 
  35 .macro kuap_save_amr_and_lock gpr1, gpr2, use_cr, msr_pr_cr
  36 #ifdef CONFIG_PPC_KUAP
  37         BEGIN_MMU_FTR_SECTION_NESTED(67)
  38         .ifnb \msr_pr_cr
  39         bne     \msr_pr_cr, 99f
  40         .endif
  41         mfspr   \gpr1, SPRN_AMR
  42         std     \gpr1, STACK_REGS_KUAP(r1)
  43         li      \gpr2, (AMR_KUAP_BLOCKED >> AMR_KUAP_SHIFT)
  44         sldi    \gpr2, \gpr2, AMR_KUAP_SHIFT
  45         cmpd    \use_cr, \gpr1, \gpr2
  46         beq     \use_cr, 99f
  47         // We don't isync here because we very recently entered via rfid
  48         mtspr   SPRN_AMR, \gpr2
  49         isync
  50 99:
  51         END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_RADIX_KUAP, 67)
  52 #endif
  53 .endm
  54 
  55 #else /* !__ASSEMBLY__ */
  56 
  57 #ifdef CONFIG_PPC_KUAP
  58 
  59 #include <asm/reg.h>
  60 
  61 /*
  62  * We support individually allowing read or write, but we don't support nesting
  63  * because that would require an expensive read/modify write of the AMR.
  64  */
  65 
  66 static inline void set_kuap(unsigned long value)
  67 {
  68         if (!early_mmu_has_feature(MMU_FTR_RADIX_KUAP))
  69                 return;
  70 
  71         /*
  72          * ISA v3.0B says we need a CSI (Context Synchronising Instruction) both
  73          * before and after the move to AMR. See table 6 on page 1134.
  74          */
  75         isync();
  76         mtspr(SPRN_AMR, value);
  77         isync();
  78 }
  79 
  80 static __always_inline void allow_user_access(void __user *to, const void __user *from,
  81                                               unsigned long size, unsigned long dir)
  82 {
  83         // This is written so we can resolve to a single case at build time
  84         BUILD_BUG_ON(!__builtin_constant_p(dir));
  85         if (dir == KUAP_READ)
  86                 set_kuap(AMR_KUAP_BLOCK_WRITE);
  87         else if (dir == KUAP_WRITE)
  88                 set_kuap(AMR_KUAP_BLOCK_READ);
  89         else
  90                 set_kuap(0);
  91 }
  92 
  93 static inline void prevent_user_access(void __user *to, const void __user *from,
  94                                        unsigned long size, unsigned long dir)
  95 {
  96         set_kuap(AMR_KUAP_BLOCKED);
  97 }
  98 
  99 static inline bool
 100 bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 101 {
 102         return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
 103                     (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
 104                     "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
 105 }
 106 #endif /* CONFIG_PPC_KUAP */
 107 
 108 #endif /* __ASSEMBLY__ */
 109 
 110 #endif /* _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H */