linux-kernel - [PATCH] objtool: Fix 64-bit build on 32-bit host

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Date:   Sat,  2 Dec 2017 16:17:44 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        linux-kernel@...r.kernel.org, Sven Joachim <svenjoac@....de>
Subject: [PATCH] objtool: Fix 64-bit build on 32-bit host

From: Mikulas Patocka <mpatocka@...hat.com>

The new ORC unwinder breaks the build of a 64-bit kernel on a 32-bit
host.  Building the kernel on a i386 or x32 host fails with:

  orc_dump.c: In function 'orc_dump':
  orc_dump.c:105:26: error: passing argument 2 of 'elf_getshdrnum' from incompatible pointer type [-Werror=incompatible-pointer-types]
    if (elf_getshdrnum(elf, &nr_sections)) {
                            ^
  In file included from /usr/local/include/gelf.h:32:0,
                   from elf.h:22,
                   from warn.h:26,
                   from orc_dump.c:20:
  /usr/local/include/libelf.h:304:12: note: expected 'size_t * {aka unsigned int *}' but argument is of type 'long unsigned int *'
   extern int elf_getshdrnum (Elf *__elf, size_t *__dst);
              ^~~~~~~~~~~~~~
  orc_dump.c:190:17: error: format '%lx' expects argument of type 'long unsigned int', but argument 3 has type 'Elf64_Sxword {aka long long int}' [-Werror=format=]
      printf("%s+%lx:", name, rela.r_addend);
                 ~~^          ~~~~~~~~~~~~~
                 %llx

Fix the build failure.

Another problem is that if the user specifies HOSTCC or HOSTLD
variables, they are ignored in the objtool makefile.  Change the
makefile to respect these variables.

Fixes: 627fce14809b ("objtool: Add ORC unwind table generation")
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/Makefile   | 8 +++++---
 tools/objtool/orc_dump.c | 8 +++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 0f94af3ccaaa..ae0272f9a091 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -7,9 +7,11 @@ ARCH := x86
 endif
 
 # always use the host compiler
-CC = gcc
-LD = ld
-AR = ar
+HOSTCC	?= gcc
+HOSTLD	?= ld
+CC	 = $(HOSTCC)
+LD	 = $(HOSTLD)
+AR	 = ar
 
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 36c5bf6a2675..301a2ae0e783 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -76,7 +76,8 @@ int orc_dump(const char *_objname)
 	int fd, nr_entries, i, *orc_ip = NULL, orc_size = 0;
 	struct orc_entry *orc = NULL;
 	char *name;
-	unsigned long nr_sections, orc_ip_addr = 0;
+	size_t nr_sections;
+	Elf64_Addr orc_ip_addr = 0;
 	size_t shstrtab_idx;
 	Elf *elf;
 	Elf_Scn *scn;
@@ -187,10 +188,11 @@ int orc_dump(const char *_objname)
 				return -1;
 			}
 
-			printf("%s+%lx:", name, rela.r_addend);
+			printf("%s+%llx:", name, (unsigned long long)rela.r_addend);
 
 		} else {
-			printf("%lx:", orc_ip_addr + (i * sizeof(int)) + orc_ip[i]);
+			printf("%llx:",
+			       (unsigned long long)(orc_ip_addr + (i * sizeof(int)) + orc_ip[i]));
 		}
 
 
-- 
2.13.6