1 files changed, 60 insertions, 132 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 84af6c8eecf7..0add963a849b 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -35,46 +35,14 @@
 
 #include <asm/firmware.h>
 #include <asm/page.h>
-#include <asm/pgtable.h>
 #include <asm/mmu.h>
 #include <asm/mmu_context.h>
 #include <asm/siginfo.h>
 #include <asm/debug.h>
 #include <asm/kup.h>
+#include <asm/inst.h>
+
 
-/*
- * Check whether the instruction inst is a store using
- * an update addressing form which will update r1.
- */
-static bool store_updates_sp(unsigned int inst)
-{
-	/* check for 1 in the rA field */
-	if (((inst >> 16) & 0x1f) != 1)
-		return false;
-	/* check major opcode */
-	switch (inst >> 26) {
-	case OP_STWU:
-	case OP_STBU:
-	case OP_STHU:
-	case OP_STFSU:
-	case OP_STFDU:
-		return true;
-	case OP_STD:	/* std or stdu */
-		return (inst & 3) == 1;
-	case OP_31:
-		/* check minor opcode */
-		switch ((inst >> 1) & 0x3ff) {
-		case OP_31_XOP_STDUX:
-		case OP_31_XOP_STWUX:
-		case OP_31_XOP_STBUX:
-		case OP_31_XOP_STHUX:
-		case OP_31_XOP_STFSUX:
-		case OP_31_XOP_STFDUX:
-			return true;
-		}
-	}
-	return false;
-}
 /*
  * do_page_fault error handling helpers
  */
@@ -108,7 +76,7 @@ static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
 	 * Something tried to access memory that isn't in our memory map..
 	 * Fix it, but check if it's kernel or user first..
 	 */
-	up_read(&mm->mmap_sem);
+	mmap_read_unlock(mm);
 
 	return __bad_area_nosemaphore(regs, address, si_code);
 }
@@ -118,9 +86,34 @@ static noinline int bad_area(struct pt_regs *regs, unsigned long address)
 	return __bad_area(regs, address, SEGV_MAPERR);
 }
 
-static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address,
-				    int pkey)
+#ifdef CONFIG_PPC_MEM_KEYS
+static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
+				    struct vm_area_struct *vma)
 {
+	struct mm_struct *mm = current->mm;
+	int pkey;
+
+	/*
+	 * We don't try to fetch the pkey from page table because reading
+	 * page table without locking doesn't guarantee stable pte value.
+	 * Hence the pkey value that we return to userspace can be different
+	 * from the pkey that actually caused access error.
+	 *
+	 * It does *not* guarantee that the VMA we find here
+	 * was the one that we faulted on.
+	 *
+	 * 1. T1   : mprotect_key(foo, PAGE_SIZE, pkey=4);
+	 * 2. T1   : set AMR to deny access to pkey=4, touches, page
+	 * 3. T1   : faults...
+	 * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
+	 * 5. T1   : enters fault handler, takes mmap_lock, etc...
+	 * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
+	 *	     faulted on a pte with its pkey=4.
+	 */
+	pkey = vma_pkey(vma);
+
+	mmap_read_unlock(mm);
+
 	/*
 	 * If we are in kernel mode, bail out with a SEGV, this will
 	 * be caught by the assembly which will restore the non-volatile
@@ -133,6 +126,7 @@ static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address,
 
 	return 0;
 }
+#endif
 
 static noinline int bad_access(struct pt_regs *regs, unsigned long address)
 {
@@ -241,56 +235,23 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
 	return false;
 }
 
-static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
-				struct vm_area_struct *vma, unsigned int flags,
-				bool *must_retry)
+#ifdef CONFIG_PPC_MEM_KEYS
+static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
+			      struct vm_area_struct *vma)
 {
 	/*
-	 * N.B. The POWER/Open ABI allows programs to access up to
-	 * 288 bytes below the stack pointer.
-	 * The kernel signal delivery code writes up to about 1.5kB
-	 * below the stack pointer (r1) before decrementing it.
-	 * The exec code can write slightly over 640kB to the stack
-	 * before setting the user r1.  Thus we allow the stack to
-	 * expand to 1MB without further checks.
+	 * Make sure to check the VMA so that we do not perform
+	 * faults just to hit a pkey fault as soon as we fill in a
+	 * page. Only called for current mm, hence foreign == 0
 	 */
-	if (address + 0x100000 < vma->vm_end) {
-		unsigned int __user *nip = (unsigned int __user *)regs->nip;
-		/* get user regs even if this fault is in kernel mode */
-		struct pt_regs *uregs = current->thread.regs;
-		if (uregs == NULL)
-			return true;
-
-		/*
-		 * A user-mode access to an address a long way below
-		 * the stack pointer is only valid if the instruction
-		 * is one which would update the stack pointer to the
-		 * address accessed if the instruction completed,
-		 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
-		 * (or the byte, halfword, float or double forms).
-		 *
-		 * If we don't check this then any write to the area
-		 * between the last mapped region and the stack will
-		 * expand the stack rather than segfaulting.
-		 */
-		if (address + 2048 >= uregs->gpr[1])
-			return false;
-
-		if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) &&
-		    access_ok(nip, sizeof(*nip))) {
-			unsigned int inst;
-
-			if (!probe_user_read(&inst, nip, sizeof(inst)))
-				return !store_updates_sp(inst);
-			*must_retry = true;
-		}
+	if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
 		return true;
-	}
+
 	return false;
 }
+#endif
 
-static bool access_error(bool is_write, bool is_exec,
-			 struct vm_area_struct *vma)
+static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
 {
 	/*
 	 * Allow execution from readable areas if the MMU does not
@@ -439,7 +400,6 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 	int is_user = user_mode(regs);
 	int is_write = page_fault_is_write(error_code);
 	vm_fault_t fault, major = 0;
-	bool must_retry = false;
 	bool kprobe_fault = kprobe_page_fault(regs, 11);
 
 	if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
@@ -483,14 +443,10 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
-	if (error_code & DSISR_KEYFAULT)
-		return bad_key_fault_exception(regs, address,
-					       get_mm_addr_key(mm, address));
-
 	/*
-	 * We want to do this outside mmap_sem, because reading code around nip
+	 * We want to do this outside mmap_lock, because reading code around nip
 	 * can result in fault, which will cause a deadlock when called with
-	 * mmap_sem held
+	 * mmap_lock held
 	 */
 	if (is_user)
 		flags |= FAULT_FLAG_USER;
@@ -502,7 +458,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 	/* When running in the kernel we expect faults to occur only to
 	 * addresses in user space.  All other faults represent errors in the
 	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
-	 * erroneous fault occurring in a code path which already holds mmap_sem
+	 * erroneous fault occurring in a code path which already holds mmap_lock
 	 * we will deadlock attempting to validate the fault against the
 	 * address space.  Luckily the kernel only validly references user
 	 * space from well defined areas of code, which are listed in the
@@ -514,12 +470,12 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 	 * source.  If this is invalid we can skip the address space check,
 	 * thus avoiding the deadlock.
 	 */
-	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
+	if (unlikely(!mmap_read_trylock(mm))) {
 		if (!is_user && !search_exception_tables(regs->nip))
 			return bad_area_nosemaphore(regs, address);
 
 retry:
-		down_read(&mm->mmap_sem);
+		mmap_read_lock(mm);
 	} else {
 		/*
 		 * The above down_read_trylock() might have succeeded in
@@ -532,29 +488,21 @@ retry:
 	vma = find_vma(mm, address);
 	if (unlikely(!vma))
 		return bad_area(regs, address);
-	if (likely(vma->vm_start <= address))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
-		return bad_area(regs, address);
 
-	/* The stack is being expanded, check if it's valid */
-	if (unlikely(bad_stack_expansion(regs, address, vma, flags,
-					 &must_retry))) {
-		if (!must_retry)
+	if (unlikely(vma->vm_start > address)) {
+		if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
 			return bad_area(regs, address);
 
-		up_read(&mm->mmap_sem);
-		if (fault_in_pages_readable((const char __user *)regs->nip,
-					    sizeof(unsigned int)))
-			return bad_area_nosemaphore(regs, address);
-		goto retry;
+		if (unlikely(expand_stack(vma, address)))
+			return bad_area(regs, address);
 	}
 
-	/* Try to expand it */
-	if (unlikely(expand_stack(vma, address)))
-		return bad_area(regs, address);
+#ifdef CONFIG_PPC_MEM_KEYS
+	if (unlikely(access_pkey_error(is_write, is_exec,
+				       (error_code & DSISR_KEYFAULT), vma)))
+		return bad_access_pkey(regs, address, vma);
+#endif /* CONFIG_PPC_MEM_KEYS */
 
-good_area:
 	if (unlikely(access_error(is_write, is_exec, vma)))
 		return bad_access(regs, address);
 
@@ -563,22 +511,7 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	fault = handle_mm_fault(vma, address, flags);
-
-#ifdef CONFIG_PPC_MEM_KEYS
-	/*
-	 * we skipped checking for access error due to key earlier.
-	 * Check that using handle_mm_fault error return.
-	 */
-	if (unlikely(fault & VM_FAULT_SIGSEGV) &&
-		!arch_vma_access_permitted(vma, is_write, is_exec, 0)) {
-
-		int pkey = vma_pkey(vma);
-
-		up_read(&mm->mmap_sem);
-		return bad_key_fault_exception(regs, address, pkey);
-	}
-#endif /* CONFIG_PPC_MEM_KEYS */
+	fault = handle_mm_fault(vma, address, flags, regs);
 
 	major |= fault & VM_FAULT_MAJOR;
 
@@ -586,7 +519,7 @@ good_area:
 		return user_mode(regs) ? 0 : SIGBUS;
 
 	/*
-	 * Handle the retry right now, the mmap_sem has been released in that
+	 * Handle the retry right now, the mmap_lock has been released in that
 	 * case.
 	 */
 	if (unlikely(fault & VM_FAULT_RETRY)) {
@@ -596,7 +529,7 @@ good_area:
 		}
 	}
 
-	up_read(&current->mm->mmap_sem);
+	mmap_read_unlock(current->mm);
 
 	if (unlikely(fault & VM_FAULT_ERROR))
 		return mm_fault_error(regs, address, fault);
@@ -604,14 +537,9 @@ good_area:
 	/*
 	 * Major/minor page fault accounting.
 	 */
-	if (major) {
-		current->maj_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
+	if (major)
 		cmo_account_page_fault();
-	} else {
-		current->min_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
-	}
+
 	return 0;
 }
 NOKPROBE_SYMBOL(__do_page_fault);