From 3a9059effb1c6ec79c6edde44d10690c43c3f52e Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Thu, 8 Aug 2019 21:40:00 +0000
Subject: [PATCH] hwasan: Add a code model check for tagged globals.

See D65364 for the code model requirements for tagged globals. Because
of the relocations used these requirements cannot be checked at link
time so they must be checked at runtime.

Differential Revision: https://reviews.llvm.org/D65968

llvm-svn: 368351
---
 compiler-rt/lib/hwasan/hwasan.cpp | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/compiler-rt/lib/hwasan/hwasan.cpp b/compiler-rt/lib/hwasan/hwasan.cpp
index f033024..999b511 100644
--- a/compiler-rt/lib/hwasan/hwasan.cpp
+++ b/compiler-rt/lib/hwasan/hwasan.cpp
@@ -240,13 +240,39 @@ struct hwasan_global_note {
   s32 end_relptr;
 };
 
+// Check that the given library meets the code model requirements for tagged
+// globals. These properties are not checked at link time so they need to be
+// checked at runtime.
+static void CheckCodeModel(ElfW(Addr) base, const ElfW(Phdr) * phdr,
+                           ElfW(Half) phnum) {
+  ElfW(Addr) min_addr = -1ull, max_addr = 0;
+  for (unsigned i = 0; i != phnum; ++i) {
+    if (phdr[i].p_type != PT_LOAD)
+      continue;
+    ElfW(Addr) lo = base + phdr[i].p_vaddr, hi = lo + phdr[i].p_memsz;
+    if (min_addr > lo)
+      min_addr = lo;
+    if (max_addr < hi)
+      max_addr = hi;
+  }
+
+  if (max_addr - min_addr > 1ull << 32) {
+    Report("FATAL: HWAddressSanitizer: library size exceeds 2^32\n");
+    Die();
+  }
+  if (max_addr > 1ull << 48) {
+    Report("FATAL: HWAddressSanitizer: library loaded above address 2^48\n");
+    Die();
+  }
+}
+
 static void InitGlobalsFromPhdrs(ElfW(Addr) base, const ElfW(Phdr) * phdr,
                                  ElfW(Half) phnum) {
-  for (; phnum != 0; ++phdr, --phnum) {
-    if (phdr->p_type != PT_NOTE)
+  for (unsigned i = 0; i != phnum; ++i) {
+    if (phdr[i].p_type != PT_NOTE)
       continue;
-    const char *note = reinterpret_cast<const char *>(base + phdr->p_vaddr);
-    const char *nend = note + phdr->p_memsz;
+    const char *note = reinterpret_cast<const char *>(base + phdr[i].p_vaddr);
+    const char *nend = note + phdr[i].p_memsz;
     while (note < nend) {
       auto *nhdr = reinterpret_cast<const ElfW(Nhdr) *>(note);
       const char *name = note + sizeof(ElfW(Nhdr));
@@ -257,6 +283,10 @@ static void InitGlobalsFromPhdrs(ElfW(Addr) base, const ElfW(Phdr) * phdr,
         continue;
       }
 
+      // Only libraries with instrumented globals need to be checked against the
+      // code model since they use relocations that aren't checked at link time.
+      CheckCodeModel(base, phdr, phnum);
+
       auto *global_note = reinterpret_cast<const hwasan_global_note *>(desc);
       auto *global_begin = reinterpret_cast<const hwasan_global *>(
           note + global_note->begin_relptr);
-- 
2.7.4