bpf: Fix cross build for CONFIG_DEBUG_INFO_BTF option

Stephen and 0-DAY CI Kernel Test Service reported broken cross build for arm (arm-linux-gnueabi-gcc (GCC) 9.3.0), with following output: /tmp/ccMS5uth.s: Assembler messages: /tmp/ccMS5uth.s:69: Error: unrecognized symbol type "" /tmp/ccMS5uth.s:82: Error: unrecognized symbol type "" Having '@object' for .type diretive is wrong because '@' is comment character for some architectures. Using STT_OBJECT instead that should work everywhere. Also using HOST* variables to build resolve_btfids so it's properly build in crossbuilds (stolen from objtool's Makefile). Reported-by: kernel test robot <[email protected]> Reported-by: Stephen Rothwell <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Tested-by: Geert Uytterhoeven <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
mjmartineau · Jul 14, 2020 · 11bb2f7 · 11bb2f7
1 parent 079ef53
commit 11bb2f7
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Showing 2 changed files with 15 additions and 1 deletion.
diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
@@ -23,7 +23,7 @@
 asm(							\
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
 ".local " #symbol " ;                          \n"	\
-".type  " #symbol ", @object;                  \n"	\
+".type  " #symbol ", STT_OBJECT;               \n"	\
 ".size  " #symbol ", 4;                        \n"	\
 #symbol ":                                     \n"	\
 ".zero 4                                       \n"	\

diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
@@ -16,6 +16,20 @@ else
   MAKEFLAGS=--no-print-directory
 endif
 
+# always use the host compiler
+ifneq ($(LLVM),)
+HOSTAR  ?= llvm-ar
+HOSTCC  ?= clang
+HOSTLD  ?= ld.lld
+else
+HOSTAR  ?= ar
+HOSTCC  ?= gcc
+HOSTLD  ?= ld
+endif
+AR       = $(HOSTAR)
+CC       = $(HOSTCC)
+LD       = $(HOSTLD)
+
 OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
 
 LIBBPF_SRC := $(srctree)/tools/lib/bpf/