[PATCH -V2 22/26] powerpc: Handle huge page in perf callchain

[Aneesh Kumar K.V]

From: "Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com>

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
 arch/powerpc/perf/callchain.c |   32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index 578cac7..99262ce 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -115,7 +115,7 @@ static int read_user_stack_slow(void __user *ptr, void *ret, int nb)
 {
 	pgd_t *pgdir;
 	pte_t *ptep, pte;
-	unsigned shift;
+	unsigned shift, hugepage;
 	unsigned long addr = (unsigned long) ptr;
 	unsigned long offset;
 	unsigned long pfn;
@@ -125,20 +125,30 @@ static int read_user_stack_slow(void __user *ptr, void *ret, int nb)
 	if (!pgdir)
 		return -EFAULT;
 
-	ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift, NULL);
+	ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift, &hugepage);
 	if (!shift)
 		shift = PAGE_SHIFT;
 
-	/* align address to page boundary */
-	offset = addr & ((1UL << shift) - 1);
-	addr -= offset;
-
-	if (ptep == NULL)
-		return -EFAULT;
-	pte = *ptep;
-	if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
+	if (!ptep)
 		return -EFAULT;
-	pfn = pte_pfn(pte);
+
+	if (hugepage) {
+		pmd_t pmd = *(pmd_t *)ptep;
+		shift = mmu_psize_defs[MMU_PAGE_16M].shift;
+		offset = addr & ((1UL << shift) - 1);
+
+		if (!pmd_large(pmd) || !(pmd_val(pmd) & PMD_HUGE_USER))
+			return -EFAULT;
+		pfn = pmd_pfn(pmd);
+	} else {
+		offset = addr & ((1UL << shift) - 1);
+
+		pte = *ptep;
+		if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
+			return -EFAULT;
+		pfn = pte_pfn(pte);
+	}
+
 	if (!page_is_ram(pfn))
 		return -EFAULT;
 
-- 
1.7.10