The semantics of DW_CFA_GNU_args_size have changed subtile over the

jsonn · jsonn · commit d0166a0a9377 · 2018-07-17T19:00:51.000Z
years. Adopt the new convention that it is call-site specific and that it should be applied before moving the IP by personality routines, but not during normal unwinding. Differential Revision: https://reviews.llvm.org/D38680 llvm-svn: 337312
diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
@@ -1411,8 +1411,6 @@ int UnwindCursor<A, R>::step() {
     this->setInfoBasedOnIPRegister(true);
     if (_unwindInfoMissing)
       return UNW_STEP_END;
-    if (_info.gp)
-      setReg(UNW_REG_SP, getReg(UNW_REG_SP) + _info.gp);
   }
 
   return result;
diff --git a/libunwind/src/libunwind.cpp b/libunwind/src/libunwind.cpp
@@ -188,8 +188,20 @@ _LIBUNWIND_EXPORT int unw_set_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
     co->setReg(regNum, (pint_t)value);
     // specical case altering IP to re-find info (being called by personality
     // function)
-    if (regNum == UNW_REG_IP)
+    if (regNum == UNW_REG_IP) {
+      unw_proc_info_t info;
+      // First, get the FDE for the old location and then update it.
+      co->getInfo(&info);
       co->setInfoBasedOnIPRegister(false);
+      // If the original call expects stack adjustment, perform this now.
+      // Normal frame unwinding would have included the offset already in the
+      // CFA computation.
+      // Note: for PA-RISC and other platforms where the stack grows up,
+      // this should actually be - info.gp. LLVM doesn't currently support
+      // any such platforms and Clang doesn't export a macro for them.
+      if (info.gp)
+        co->setReg(UNW_REG_SP, co->getReg(UNW_REG_SP) + info.gp);
+    }
     return UNW_ESUCCESS;
   }
   return UNW_EBADREG;

Original file line number	Diff line number	Diff line change
`@@ -1411,8 +1411,6 @@ int UnwindCursor<A, R>::step() {`
`1411`	`1411`	`this->setInfoBasedOnIPRegister(true);`
`1412`	`1412`	`if (_unwindInfoMissing)`
`1413`	`1413`	`return UNW_STEP_END;`
`1414`		`- if (_info.gp)`
`1415`		`- setReg(UNW_REG_SP, getReg(UNW_REG_SP) + _info.gp);`
`1416`	`1414`	`}`
`1417`	`1415`
`1418`	`1416`	`return result;`