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Message-Id: <1352281674-2186-23-git-send-email-vgupta@synopsys.com>
Date: Wed, 7 Nov 2012 10:47:45 +0100
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de, arnd@...db.de,
Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [RFC PATCH v1 22/31] ARC: Page Fault handling (incl uaccess fixup)
This includes recent changes to make handler "retry" and/or "killable"
The killable (early exit) logic is loosely based on how SH implements it
return if SIGKILL + either of VM_FAULT_OOM or VM_FAULT_RETRY
which is different from Hexagon implementation which would NOT early
exit for
SIGKILL + VM_FAULT_OOM + !VM_FAULT_RETRY
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
arch/arc/mm/extable.c | 26 ++++++
arch/arc/mm/fault.c | 228 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 254 insertions(+), 0 deletions(-)
create mode 100644 arch/arc/mm/extable.c
create mode 100644 arch/arc/mm/fault.c
diff --git a/arch/arc/mm/extable.c b/arch/arc/mm/extable.c
new file mode 100644
index 0000000..f05b677
--- /dev/null
+++ b/arch/arc/mm/extable.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Borrowed heavily from MIPS
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+int fixup_exception(struct pt_regs *regs)
+{
+ const struct exception_table_entry *fixup;
+
+ fixup = search_exception_tables(instruction_pointer(regs));
+ if (fixup) {
+ regs->ret = fixup->fixup;
+
+ return 1;
+ }
+
+ return 0;
+}
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
new file mode 100644
index 0000000..af55aab
--- /dev/null
+++ b/arch/arc/mm/fault.c
@@ -0,0 +1,228 @@
+/* Page Fault Handling for ARC (TLB Miss / ProtV)
+ *
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/signal.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/ptrace.h>
+#include <linux/version.h>
+#include <linux/uaccess.h>
+#include <linux/kdebug.h>
+#include <asm/pgalloc.h>
+
+static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address)
+{
+ /*
+ * Synchronize this task's top level page-table
+ * with the 'reference' page table.
+ */
+ pgd_t *pgd, *pgd_k;
+ pud_t *pud, *pud_k;
+ pmd_t *pmd, *pmd_k;
+
+ pgd = pgd_offset_fast(mm, address);
+ pgd_k = pgd_offset_k(address);
+
+ if (!pgd_present(*pgd_k))
+ goto bad_area;
+
+ pud = pud_offset(pgd, address);
+ pud_k = pud_offset(pgd_k, address);
+ if (!pud_present(*pud_k))
+ goto bad_area;
+
+ pmd = pmd_offset(pud, address);
+ pmd_k = pmd_offset(pud_k, address);
+ if (!pmd_present(*pmd_k))
+ goto bad_area;
+
+ set_pmd(pmd, *pmd_k);
+
+ /* XXX: create the TLB entry here */
+ return 0;
+
+bad_area:
+ return 1;
+}
+
+void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
+ unsigned long cause_code)
+{
+ struct vm_area_struct *vma = NULL;
+ struct task_struct *tsk = current;
+ struct mm_struct *mm = tsk->mm;
+ siginfo_t info;
+ int fault, ret;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+ (write ? FAULT_FLAG_WRITE : 0);
+
+ /*
+ * We fault-in kernel-space virtual memory on-demand. The
+ * 'reference' page table is init_mm.pgd.
+ *
+ * NOTE! We MUST NOT take any locks for this case. We may
+ * be in an interrupt or a critical region, and should
+ * only copy the information from the master page table,
+ * nothing more.
+ */
+ if (address >= VMALLOC_START && address <= VMALLOC_END) {
+ ret = handle_vmalloc_fault(mm, address);
+ if (unlikely(ret))
+ goto bad_area_nosemaphore;
+ else
+ return;
+ }
+
+ info.si_code = SEGV_MAPERR;
+
+ /*
+ * If we're in an interrupt or have no user
+ * context, we must not take the fault..
+ */
+ if (in_atomic() || !mm)
+ goto no_context;
+
+retry:
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, address);
+ if (!vma)
+ goto bad_area;
+ if (vma->vm_start <= address)
+ goto good_area;
+ if (!(vma->vm_flags & VM_GROWSDOWN))
+ goto bad_area;
+ if (expand_stack(vma, address))
+ goto bad_area;
+
+ /*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+good_area:
+ info.si_code = SEGV_ACCERR;
+
+ /* Handle protection violation, execute on heap or stack */
+
+ if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
+ goto bad_area;
+
+ if (write) {
+ if (!(vma->vm_flags & VM_WRITE))
+ goto bad_area;
+ } else {
+ if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+ goto bad_area;
+ }
+
+survive:
+ /*
+ * If for any reason at all we couldn't handle the fault,
+ * make sure we exit gracefully rather than endlessly redo
+ * the fault.
+ */
+ fault = handle_mm_fault(mm, vma, address, flags);
+
+ /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
+ if (unlikely(fatal_signal_pending(current))) {
+ if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
+ up_read(&mm->mmap_sem);
+ if (user_mode(regs))
+ return;
+ }
+
+ if (likely(!(fault & VM_FAULT_ERROR))) {
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ /* To avoid updating stats twice for retry case */
+ if (fault & VM_FAULT_MAJOR)
+ tsk->maj_flt++;
+ else
+ tsk->min_flt++;
+
+ if (fault & VM_FAULT_RETRY) {
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags |= FAULT_FLAG_TRIED;
+ goto retry;
+ }
+ }
+
+ /* Fault Handled Gracefully */
+ up_read(&mm->mmap_sem);
+ return;
+ }
+
+ /* TBD: switch to pagefault_out_of_memory() */
+ if (fault & VM_FAULT_OOM)
+ goto out_of_memory;
+ else if (fault & VM_FAULT_SIGBUS)
+ goto do_sigbus;
+
+ /* no man's land */
+ BUG();
+
+ /*
+ * Something tried to access memory that isn't in our memory map..
+ * Fix it, but check if it's kernel or user first..
+ */
+bad_area:
+ up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+ /* User mode accesses just cause a SIGSEGV */
+ if (user_mode(regs)) {
+ tsk->thread.fault_address = address;
+ tsk->thread.cause_code = cause_code;
+ info.si_signo = SIGSEGV;
+ info.si_errno = 0;
+ /* info.si_code has been set above */
+ info.si_addr = (void __user *)address;
+ force_sig_info(SIGSEGV, &info, tsk);
+ return;
+ }
+
+no_context:
+ /* Are we prepared to handle this kernel fault?
+ *
+ * (The kernel has valid exception-points in the source
+ * when it acesses user-memory. When it fails in one
+ * of those points, we find it in a table and do a jump
+ * to some fixup code that loads an appropriate error
+ * code)
+ */
+ if (fixup_exception(regs))
+ return;
+
+ die("Oops", regs, address, cause_code);
+
+out_of_memory:
+ if (is_global_init(tsk)) {
+ yield();
+ goto survive;
+ }
+ up_read(&mm->mmap_sem);
+
+ if (user_mode(regs))
+ do_group_exit(SIGKILL); /* This will never return */
+
+ goto no_context;
+
+do_sigbus:
+ up_read(&mm->mmap_sem);
+
+ if (!user_mode(regs))
+ goto no_context;
+
+ tsk->thread.fault_address = address;
+ tsk->thread.cause_code = cause_code;
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = BUS_ADRERR;
+ info.si_addr = (void __user *)address;
+ force_sig_info(SIGBUS, &info, tsk);
+}
--
1.7.4.1
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