From: YiFei Zhu <zhuyifei1999@gmail.com>
Date: Thu, 22 Apr 2021 10:05:57 +0000 (-0500)
Subject: bpf: allow BSS symbols to be global symbols
X-Git-Tag: basepoints/gcc-13~8217
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=886b6c1e8af502b69e3f318b9830b73b88215878;p=thirdparty%2Fgcc.git

bpf: allow BSS symbols to be global symbols

Prior to this, a BSS declaration such as:

  int foo;
  static int bar;

Generates:

  .global foo
  .local  foo
  .comm   foo,4,4
  .local  bar
  .comm	  bar,4,4

Creating symbols:

  0000000000000000 b foo
  0000000000000004 b bar

Both symbols are local. However, libbpf bpf_object__variable_offset
rquires symbols to be STB_GLOBAL & STT_OBJECT for data section lookup.
This patch makes the same declaration generate:

  .global foo
  .type   foo, @object
  .lcomm  foo,4,4
  .local  bar
  .comm   bar,4,4

Creating symbols:

  0000000000000000 B foo
  0000000000000004 b bar

And libbpf will be okay with looking up the global symbol "foo".

2021-04-22  YiFei Zhu  <zhuyifei1999@gmail.com>

gcc/

	* config/bpf/bpf.h (ASM_OUTPUT_ALIGNED_BSS): Use .type and .lcomm.
---

diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
index 6a3907fb6181..4c5b19e262b9 100644
--- a/gcc/config/bpf/bpf.h
+++ b/gcc/config/bpf/bpf.h
@@ -422,9 +422,15 @@ enum reg_class
    Try to use asm_output_aligned_bss to implement this macro.  */
 
 #define ASM_OUTPUT_ALIGNED_BSS(FILE, DECL, NAME, SIZE, ALIGN)	\
-  do {								\
-    ASM_OUTPUT_ALIGNED_LOCAL (FILE, NAME, SIZE, ALIGN);		\
-  } while (0)
+  do									\
+    {									\
+      ASM_OUTPUT_TYPE_DIRECTIVE (FILE, NAME, "object");			\
+      fprintf ((FILE), "%s", "\t.lcomm\t");				\
+      assemble_name ((FILE), (NAME));					\
+      fprintf ((FILE), "," HOST_WIDE_INT_PRINT_UNSIGNED ",%u\n",	\
+	       (SIZE), (ALIGN) / BITS_PER_UNIT);			\
+    }									\
+  while (0)
 
 /*** Output and Generation of Labels.  */