[RFC][PATCH 4/X][libsanitizer] Pass size and pointer info to error reporting functions

[Matthew Malcomson]

This makes the error reporting for loadN and storeN much better.
In this first draft these are the only functions I will be using and
hence this fix is very useful.

This is taken from upstream LLVM (change made in LLVM svn commit
351730), but is not a direct cherry-pick of a commit since the commit
does not apply cleanly.

libsanitizer/ChangeLog:

2019-09-06  Matthew Malcomson  <matthew.malcom...@arm.com>

        * hwasan/hwasan.cc (CheckAddressSized): Use new sized SigTrap.
        (SigTrap): Record pointer in x0 for error report and add an
        overloaded version that takes both pointer and size.



###############     Attachment also inlined for ease of reply    ###############


diff --git a/libsanitizer/hwasan/hwasan.cc b/libsanitizer/hwasan/hwasan.cc
index 
518cd11ff301f1d1cf6f5275ecffdb03d880d8d1..a2ad8f96d847d5c4395da668a40b24f5331dcbd6
 100644
--- a/libsanitizer/hwasan/hwasan.cc
+++ b/libsanitizer/hwasan/hwasan.cc
@@ -360,8 +360,8 @@ static void SigTrap(uptr p) {
   (void)p;
   // 0x900 is added to do not interfere with the kernel use of lower values of
   // brk immediate.
-  // FIXME: Add a constraint to put the pointer into x0, the same as x86 
branch.
-  asm("brk %0\n\t" ::"n"(0x900 + X));
+  register uptr x0 asm("x0") = p;
+  asm("brk %1\n\t" ::"r"(x0), "n"(0x900 + X));
 #elif defined(__x86_64__)
   // INT3 + NOP DWORD ptr [EAX + X] to pass X to our signal handler, 5 bytes
   // total. The pointer is passed via rdi.
@@ -379,6 +379,25 @@ static void SigTrap(uptr p) {
   // __builtin_unreachable();
 }
 
+template <unsigned X>
+__attribute__((always_inline)) static void SigTrap(uptr p, uptr size) {
+#if defined(__aarch64__)
+  register uptr x0 asm("x0") = p;
+  register uptr x1 asm("x1") = size;
+  asm("brk %2\n\t" ::"r"(x0), "r"(x1), "n"(0x900 + X));
+#elif defined(__x86_64__)
+  // Size is stored in rsi.
+  asm volatile(
+      "int3\n"
+      "nopl %c0(%%rax)\n" ::"n"(0x40 + X),
+      "D"(p), "S"(size));
+#else
+  __builtin_trap();
+#endif
+  // __builtin_unreachable();
+}
+
+
 enum class ErrorAction { Abort, Recover };
 enum class AccessType { Load, Store };
 
@@ -405,7 +424,7 @@ __attribute__((always_inline, nodebug)) static void 
CheckAddressSized(uptr p,
   for (tag_t *t = shadow_first; t <= shadow_last; ++t)
     if (UNLIKELY(ptr_tag != *t)) {
       SigTrap<0x20 * (EA == ErrorAction::Recover) +
-             0x10 * (AT == AccessType::Store) + 0xf>(p);
+             0x10 * (AT == AccessType::Store) + 0xf>(p, sz);
       if (EA == ErrorAction::Abort) __builtin_unreachable();
     }
 }


diff --git a/libsanitizer/hwasan/hwasan.cc b/libsanitizer/hwasan/hwasan.cc
index 
518cd11ff301f1d1cf6f5275ecffdb03d880d8d1..a2ad8f96d847d5c4395da668a40b24f5331dcbd6
 100644
--- a/libsanitizer/hwasan/hwasan.cc
+++ b/libsanitizer/hwasan/hwasan.cc
@@ -360,8 +360,8 @@ static void SigTrap(uptr p) {
   (void)p;
   // 0x900 is added to do not interfere with the kernel use of lower values of
   // brk immediate.
-  // FIXME: Add a constraint to put the pointer into x0, the same as x86 
branch.
-  asm("brk %0\n\t" ::"n"(0x900 + X));
+  register uptr x0 asm("x0") = p;
+  asm("brk %1\n\t" ::"r"(x0), "n"(0x900 + X));
 #elif defined(__x86_64__)
   // INT3 + NOP DWORD ptr [EAX + X] to pass X to our signal handler, 5 bytes
   // total. The pointer is passed via rdi.
@@ -379,6 +379,25 @@ static void SigTrap(uptr p) {
   // __builtin_unreachable();
 }
 
+template <unsigned X>
+__attribute__((always_inline)) static void SigTrap(uptr p, uptr size) {
+#if defined(__aarch64__)
+  register uptr x0 asm("x0") = p;
+  register uptr x1 asm("x1") = size;
+  asm("brk %2\n\t" ::"r"(x0), "r"(x1), "n"(0x900 + X));
+#elif defined(__x86_64__)
+  // Size is stored in rsi.
+  asm volatile(
+      "int3\n"
+      "nopl %c0(%%rax)\n" ::"n"(0x40 + X),
+      "D"(p), "S"(size));
+#else
+  __builtin_trap();
+#endif
+  // __builtin_unreachable();
+}
+
+
 enum class ErrorAction { Abort, Recover };
 enum class AccessType { Load, Store };
 
@@ -405,7 +424,7 @@ __attribute__((always_inline, nodebug)) static void 
CheckAddressSized(uptr p,
   for (tag_t *t = shadow_first; t <= shadow_last; ++t)
     if (UNLIKELY(ptr_tag != *t)) {
       SigTrap<0x20 * (EA == ErrorAction::Recover) +
-             0x10 * (AT == AccessType::Store) + 0xf>(p);
+             0x10 * (AT == AccessType::Store) + 0xf>(p, sz);
       if (EA == ErrorAction::Abort) __builtin_unreachable();
     }
 }