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Message-Id: <20210830173844.458727-2-hjl.tools@gmail.com>
Date: Mon, 30 Aug 2021 10:38:43 -0700
From: "H.J. Lu" <hjl.tools@...il.com>
To: libc-alpha@...rceware.org
Cc: gdb@...rceware.org,
	libc-coord@...ts.openwall.com,
	Florian Weimer <fweimer@...hat.com>,
	Daniel Walker <danielwa@...co.com>
Subject: [PATCH v6 1/2] Add declare_object_symbol_alias for assembly codes [BZ #28128]

There are 2 problems in:

 #define declare_symbol_alias(symbol, original, type, size) \
  declare_symbol_alias_1 (symbol, original, type, size)
 #ifdef __ASSEMBLER__
 # define declare_symbol_alias_1(symbol, original, type, size) \
   strong_alias (original, symbol); \
   .type C_SYMBOL_NAME (symbol), %##type; \
   .size C_SYMBOL_NAME (symbol), size

1. .type and .size are substituted by arguments.
2. %##type is expanded to "% type" due to the GCC bug:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101613

But assembler doesn't support "% type".

Workaround BZ #28128 by

1. Don't define declare_symbol_alias for assembly codes.
2. Define declare_object_symbol_alias for assembly codes.
---
 include/libc-symbols.h | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index d41ecf4384..1678071d77 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -324,14 +324,16 @@ for linking")
    This is only necessary when defining something in assembly, or playing
    funny alias games where the size should be other than what the compiler
    thinks it is.  */
-#define declare_symbol_alias(symbol, original, type, size) \
-  declare_symbol_alias_1 (symbol, original, type, size)
 #ifdef __ASSEMBLER__
-# define declare_symbol_alias_1(symbol, original, type, size) \
+# define declare_object_symbol_alias(symbol, original, size) \
+  declare_object_symbol_alias_1 (symbol, original, size)
+# define declare_object_symbol_alias_1(symbol, original, s_size) \
    strong_alias (original, symbol); \
-   .type C_SYMBOL_NAME (symbol), %##type; \
-   .size C_SYMBOL_NAME (symbol), size
+   .type C_SYMBOL_NAME (symbol), %object; \
+   .size C_SYMBOL_NAME (symbol), s_size
 #else /* Not __ASSEMBLER__.  */
+# define declare_symbol_alias(symbol, original, type, size) \
+  declare_symbol_alias_1 (symbol, original, type, size)
 # define declare_symbol_alias_1(symbol, original, type, size) \
    asm (".globl " __SYMBOL_PREFIX #symbol \
 	"\n\t" declare_symbol_alias_1_alias (symbol, original) \
-- 
2.31.1

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