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Subject[PATCH] arch/tile: fix two bugs in the backtracer code
The first is that we were using an incorrect hand-rolled variant
of __kernel_text_address() which didn't handle module PCs. We now
just use the standard API.

The second was that we weren't accounting for the three-level
page table when we were trying to pre-verify the addresses on
the 64-bit TILE-Gx processor; we now do that correctly.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
---
arch/tile/kernel/stack.c | 28 +++++++++++++++++++---------
1 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index 0d54106..dd81713 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -44,13 +44,6 @@ static int in_kernel_stack(struct KBacktraceIterator *kbt, VirtualAddress sp)
return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
}

-/* Is address in the specified kernel code? */
-static int in_kernel_text(VirtualAddress address)
-{
- return (address >= MEM_SV_INTRPT &&
- address < MEM_SV_INTRPT + HPAGE_SIZE);
-}
-
/* Is address valid for reading? */
static int valid_address(struct KBacktraceIterator *kbt, VirtualAddress address)
{
@@ -63,6 +56,23 @@ static int valid_address(struct KBacktraceIterator *kbt, VirtualAddress address)
if (l1_pgtable == NULL)
return 0; /* can't read user space in other tasks */

+#ifdef CONFIG_64BIT
+ /* Find the real l1_pgtable by looking in the l0_pgtable. */
+ pte = l1_pgtable[HV_L0_INDEX(address)];
+ if (!hv_pte_get_present(pte))
+ return 0;
+ pfn = hv_pte_get_pfn(pte);
+ if (pte_huge(pte)) {
+ if (!pfn_valid(pfn)) {
+ pr_err("L0 huge page has bad pfn %#lx\n", pfn);
+ return 0;
+ }
+ return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
+ }
+ page = pfn_to_page(pfn);
+ BUG_ON(PageHighMem(page)); /* No HIGHMEM on 64-bit. */
+ l1_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
+#endif
pte = l1_pgtable[HV_L1_INDEX(address)];
if (!hv_pte_get_present(pte))
return 0;
@@ -92,7 +102,7 @@ static bool read_memory_func(void *result, VirtualAddress address,
{
int retval;
struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
- if (in_kernel_text(address)) {
+ if (__kernel_text_address(address)) {
/* OK to read kernel code. */
} else if (address >= PAGE_OFFSET) {
/* We only tolerate kernel-space reads of this task's stack */
@@ -132,7 +142,7 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
}
}
if (EX1_PL(p->ex1) == KERNEL_PL &&
- in_kernel_text(p->pc) &&
+ __kernel_text_address(p->pc) &&
in_kernel_stack(kbt, p->sp) &&
p->sp >= sp) {
if (kbt->verbose)
--
1.6.5.2


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