Make text section 2MB aligned for hugepages.

chromeos/hugepage_text/hugepage_text.cc

Index: chromeos/hugepage_text/hugepage_text.cc
diff --git a/chromeos/hugepage_text/hugepage_text.cc b/chromeos/hugepage_text/hugepage_text.cc
index ccae53f723fdbd9e181f5421fd82c2fdc851062b..dd2dcf4a572c4ee98a2bcf1342abea06512f1634 100644
--- a/chromeos/hugepage_text/hugepage_text.cc
+++ b/chromeos/hugepage_text/hugepage_text.cc
@@ -172,7 +172,11 @@ static void MremapHugetlbText(void* vaddr, const size_t hsize) {
 // Effect: physical backing page changed from small page to hugepage. If there
 //         are error condition, the remaping operation is aborted.
 static void RemapHugetlbText(void* vaddr, const size_t segsize) {
-  int hsize = segsize;
+  // remove unaligned head regions
+  size_t head_gap = (kHpageSize - (size_t)addr % kHpageSize) % kHpageSize;

[kenchen, 2016/01/22 22:19:42]

This should vaddr and the last mod operation is not necessary.

[yunlian, 2016/01/22 22:27:00]

Yes, the vaddr is part is done. The last mod is useful when the vaddr is 2MB
aligned. In this case, the head_gap is 0 instead of kHpageSize

+  size_t addr = (size_t)vaddr + head_gap;
+
+  int hsize = segsize - head_gap;
   if (segsize > kHpageSize * kNumHugePages)
     hsize = kHpageSize * kNumHugePages;
   hsize = hsize & kHpageMask;
@@ -180,7 +184,7 @@ static void RemapHugetlbText(void* vaddr, const size_t segsize) {
   if (hsize == 0)
     return;
 
-  MremapHugetlbText(vaddr, hsize);
+  MremapHugetlbText((void *)addr, hsize);
 }
 
 // For a given ELF program header descriptor, iterates over all segments within