From: Vineet Gupta Date: Mon, 17 Jun 2013 12:42:13 +0000 (+0530) Subject: ARC: [PTE] Fold PTE K/U access flags (MMUv4 preps) X-Git-Tag: next-20130619~114^2 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=21a229960e9f6927519c88ca721587c668eeadf5;p=karo-tx-linux.git ARC: [PTE] Fold PTE K/U access flags (MMUv4 preps) The current ARC VM code has 13 flags in Page Table entry: some software (accesed/dirty/non-linear-maps) and rest hardware specific. With 8k MMU page, we need 19 bits for addressing page frame so remaining 13 bits is just about enough to accomodate the current flags. In MMUv4 there are 2 additional flags, SZ (normal or super page) and WT (cache access mode write-thru) - and additionally PFN is 20 bits (vs. 19 before for 8k). Thus these can't be held in current PTE w/o making each entry 64bit wide. It seems there is some scope of compressing the current PTE flags (and freeing up a few bits). Currently PTE contains fully orthogonal distinct access permissions for kernel and user mode (Kr, Kw, Kx; Ur, Uw, Ux) which can be folded into one set (R, W, X). The translation of 3 PTE bits into 6 TLB bits (when programming the MMU) can be done based on following pre-requites/assumptions: 1. For kernel-mode-only translations (vmalloc: 0x7000_0000 to 0x7FFF_FFFF), PTE additionally has PAGE_GLOBAL flag set (and user space entries can never be global). Thus such a PTE can translate to Kr, Kw, Kx (as appropriate) and zero for User mode counterparts. 2. For non global entries, the PTE flags can be used to create mirrored K and U TLB bits. This is true after commit a950549c675f2c8c504 "ARC: copy_(to|from)_user() to honor usermode-access permissions" which ensured that user-space translations _MUST_ have same access permissions for both U/K mode accesses so that copy_{to,from}_user() play fair with fault based CoW break and such... There is no such thing as free lunch - the cost is slightly infalted TLB-Miss Handlers. Signed-off-by: Vineet Gupta --- diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h index fd57524c0b5b..8063d6a04538 100644 --- a/arch/arc/include/asm/pgtable.h +++ b/arch/arc/include/asm/pgtable.h @@ -57,27 +57,21 @@ #define _PAGE_ACCESSED (1<<1) /* Page is accessed (S) */ #define _PAGE_CACHEABLE (1<<2) /* Page is cached (H) */ -#define _PAGE_U_EXECUTE (1<<3) /* Page has user execute perm (H) */ -#define _PAGE_U_WRITE (1<<4) /* Page has user write perm (H) */ -#define _PAGE_U_READ (1<<5) /* Page has user read perm (H) */ -#define _PAGE_K_EXECUTE (1<<6) /* Page has kernel execute perm (H) */ -#define _PAGE_K_WRITE (1<<7) /* Page has kernel write perm (H) */ -#define _PAGE_K_READ (1<<8) /* Page has kernel perm (H) */ +#define _PAGE_EXECUTE (1<<3) /* Page has user execute perm (H) */ +#define _PAGE_WRITE (1<<4) /* Page has user write perm (H) */ +#define _PAGE_READ (1<<5) /* Page has user read perm (H) */ #define _PAGE_GLOBAL (1<<9) /* Page is global (H) */ #define _PAGE_MODIFIED (1<<10) /* Page modified (dirty) (S) */ #define _PAGE_FILE (1<<10) /* page cache/ swap (S) */ #define _PAGE_PRESENT (1<<11) /* TLB entry is valid (H) */ -#else +#else /* MMU v3 onwards */ /* PD1 */ #define _PAGE_CACHEABLE (1<<0) /* Page is cached (H) */ -#define _PAGE_U_EXECUTE (1<<1) /* Page has user execute perm (H) */ -#define _PAGE_U_WRITE (1<<2) /* Page has user write perm (H) */ -#define _PAGE_U_READ (1<<3) /* Page has user read perm (H) */ -#define _PAGE_K_EXECUTE (1<<4) /* Page has kernel execute perm (H) */ -#define _PAGE_K_WRITE (1<<5) /* Page has kernel write perm (H) */ -#define _PAGE_K_READ (1<<6) /* Page has kernel perm (H) */ +#define _PAGE_EXECUTE (1<<1) /* Page has user execute perm (H) */ +#define _PAGE_WRITE (1<<2) /* Page has user write perm (H) */ +#define _PAGE_READ (1<<3) /* Page has user read perm (H) */ #define _PAGE_ACCESSED (1<<7) /* Page is accessed (S) */ /* PD0 */ @@ -92,8 +86,8 @@ #define _PAGE_SHARED_CODE_H (1<<31) /* Hardware counterpart of above */ #endif -/* Kernel allowed all permissions for all pages */ -#define _K_PAGE_PERMS (_PAGE_K_EXECUTE | _PAGE_K_WRITE | _PAGE_K_READ | \ +/* vmalloc permissions */ +#define _K_PAGE_PERMS (_PAGE_EXECUTE | _PAGE_WRITE | _PAGE_READ | \ _PAGE_GLOBAL | _PAGE_PRESENT) #ifdef CONFIG_ARC_CACHE_PAGES @@ -109,10 +103,6 @@ */ #define ___DEF (_PAGE_PRESENT | _PAGE_DEF_CACHEABLE) -#define _PAGE_READ (_PAGE_U_READ | _PAGE_K_READ) -#define _PAGE_WRITE (_PAGE_U_WRITE | _PAGE_K_WRITE) -#define _PAGE_EXECUTE (_PAGE_U_EXECUTE | _PAGE_K_EXECUTE) - /* Set of bits not changed in pte_modify */ #define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_MODIFIED) @@ -126,8 +116,8 @@ #define PAGE_SHARED PAGE_U_W_R -/* While kernel runs out of unstrslated space, vmalloc/modules use a chunk of - * kernel vaddr space - visible in all addr spaces, but kernel mode only +/* While kernel runs out of unstranslated space, vmalloc/modules use a chunk of + * user vaddr space - visible in all addr spaces, but kernel mode only * Thus Global, all-kernel-access, no-user-access, cached */ #define PAGE_KERNEL __pgprot(_K_PAGE_PERMS | _PAGE_DEF_CACHEABLE) diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c index d44ae33c2d1e..7386476aaf47 100644 --- a/arch/arc/mm/tlb.c +++ b/arch/arc/mm/tlb.c @@ -341,8 +341,8 @@ void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page) void create_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep) { unsigned long flags; - unsigned int idx, asid_or_sasid; - unsigned long pd0_flags; + unsigned int idx, asid_or_sasid, rwx; + unsigned long pd0_flags, pte, pfn_etc; /* * create_tlb() assumes that current->mm == vma->mm, since @@ -393,8 +393,17 @@ void create_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep) write_aux_reg(ARC_REG_TLBPD0, address | pd0_flags | asid_or_sasid); + pte = pte_val(*ptep); + rwx = pte & PTE_BITS_RWX; + pfn_etc = pte & PTE_BITS_NON_RWX_IN_PD1; + + if (pte & _PAGE_GLOBAL) + rwx <<= 3; /* r w x => Kr Kw Kx 0 0 0 */ + else + rwx |= (rwx << 3); /* r w x => Kr Kw Kx Ur Uw Ux */ + /* Load remaining info in PD1 (Page Frame Addr and Kx/Kw/Kr Flags) */ - write_aux_reg(ARC_REG_TLBPD1, (pte_val(*ptep) & PTE_BITS_IN_PD1)); + write_aux_reg(ARC_REG_TLBPD1, rwx | pfn_etc); /* First verify if entry for this vaddr+ASID already exists */ write_aux_reg(ARC_REG_TLBCOMMAND, TLBProbe); diff --git a/arch/arc/mm/tlbex.S b/arch/arc/mm/tlbex.S index 5c5bb23001b0..987db36e26c5 100644 --- a/arch/arc/mm/tlbex.S +++ b/arch/arc/mm/tlbex.S @@ -161,8 +161,15 @@ ex_saved_reg1: ; IN: r0 = PTE, r1 = ptr to PTE .macro CONV_PTE_TO_TLB - and r3, r0, PTE_BITS_IN_PD1 ; Extract permission flags+PFN from PTE - sr r3, [ARC_REG_TLBPD1] ; these go in PD1 + and r3, r0, PTE_BITS_RWX ; r w x + lsl r2, r3, 3 ; r w x 0 0 0 + and.f 0, r0, _PAGE_GLOBAL + or.z r2, r2, r3 ; r w x r w x + + and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE + or r3, r3, r2 + + sr r3, [ARC_REG_TLBPD1] ; these go in PD1 and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb #if (CONFIG_ARC_MMU_VER <= 2) /* Neednot be done with v3 onwards */ @@ -277,8 +284,8 @@ ARC_ENTRY EV_TLBMissI ;---------------------------------------------------------------- ; VERIFY_PTE: Check if PTE permissions approp for executing code cmp_s r2, VMALLOC_START - mov.lo r2, (_PAGE_PRESENT | _PAGE_U_EXECUTE) - mov.hs r2, (_PAGE_PRESENT | _PAGE_K_EXECUTE) + mov_s r2, (_PAGE_PRESENT | _PAGE_EXECUTE) + or.hs r2, r2, _PAGE_GLOBAL and r3, r0, r2 ; Mask out NON Flag bits from PTE xor.f r3, r3, r2 ; check ( ( pte & flags_test ) == flags_test ) @@ -317,26 +324,21 @@ ARC_ENTRY EV_TLBMissD ;---------------------------------------------------------------- ; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W) - mov_s r2, 0 + cmp_s r2, VMALLOC_START + mov_s r2, _PAGE_PRESENT ; common bit for K/U PTE + or.hs r2, r2, _PAGE_GLOBAL ; kernel PTE only + + ; Linux PTE [RWX] bits are semantically overloaded: + ; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc) + ; -Otherwise they are user-mode permissions, and those are exactly + ; same for kernel mode as well (e.g. copy_(to|from)_user) + lr r3, [ecr] btst_s r3, ECR_C_BIT_DTLB_LD_MISS ; Read Access - or.nz r2, r2, _PAGE_U_READ ; chk for Read flag in PTE + or.nz r2, r2, _PAGE_READ ; chk for Read flag in PTE btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; Write Access - or.nz r2, r2, _PAGE_U_WRITE ; chk for Write flag in PTE - ; Above laddering takes care of XCHG access - ; which is both Read and Write - - ; If kernel mode access, ; make _PAGE_xx flags as _PAGE_K_xx - ; For copy_(to|from)_user, despite exception taken in kernel mode, - ; this code is not hit, because EFA would still be the user mode - ; address (EFA < 0x6000_0000). - ; This code is for legit kernel mode faults, vmalloc specifically - ; (EFA: 0x7000_0000 to 0x7FFF_FFFF) - - lr r3, [efa] - cmp r3, VMALLOC_START - 1 ; If kernel mode access - asl.hi r2, r2, 3 ; make _PAGE_xx flags as _PAGE_K_xx - or r2, r2, _PAGE_PRESENT ; Common flag for K/U mode + or.nz r2, r2, _PAGE_WRITE ; chk for Write flag in PTE + ; Above laddering takes care of XCHG access (both R and W) ; By now, r2 setup with all the Flags we need to check in PTE and r3, r0, r2 ; Mask out NON Flag bits from PTE