[PATCH 1/2] x86_64: Reflect the relocatability of the kernel in the ELF header.

Eric W. Biederman
2007-04-23T05:18:06Z

Currently because vmlinux does not reflect that the kernel is relocatable
we still have to support CONFIG_PHYSICAL_START. So this patch adds a small
c program to do what we cannot do with a linker script, set the elf header
type to ET_DYN.

This should remove the last obstacle to removing CONFIG_PHYSICAL_START
on x86_64.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
arch/x86_64/Kconfig | 4 +++
arch/x86_64/Makefile | 10 +++++++
scripts/Makefile | 11 ++++---
scripts/mketrel.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 90 insertions(+), 5 deletions(-)
create mode 100644 scripts/mketrel.c

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 16d9bf3..773b487 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -121,6 +121,10 @@ config ARCH_HAS_ILOG2_U64
bool
default n

+config ELF_RELOCATABLE
+ bool
+ default y
+
source "init/Kconfig"

diff --git a/arch/x86_64/Makefile b/arch/x86_64/Makefile
index 9dd91b2..5ae79ab 100644
--- a/arch/x86_64/Makefile
+++ b/arch/x86_64/Makefile
@@ -124,6 +124,16 @@ define archhelp
echo ' isoimage - Create a boot CD-ROM image'
endef

+ifeq ($(CONFIG_RELOCATABLE),y)
+define cmd_vmlinux__
+ $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) -o $@ \
+ -T $(vmlinux-lds) $(vmlinux-init) \
+ --start-group $(vmlinux-main) --end-group \
+ $(filter-out $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) FORCE ,$^) \
+ && scripts/mketrel $@
+endef
+endif
+
CLEAN_FILES += arch/$(ARCH)/boot/fdimage \
arch/$(ARCH)/boot/image.iso \
arch/$(ARCH)/boot/mtools.conf
diff --git a/scripts/Makefile b/scripts/Makefile
index 1c73c5a..ddba550 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -7,11 +7,12 @@
# conmakehash: Create chartable
# conmakehash: Create arrays for initializing the kernel console tables

-hostprogs-$(CONFIG_KALLSYMS) += kallsyms
-hostprogs-$(CONFIG_LOGO) += pnmtologo
-hostprogs-$(CONFIG_VT) += conmakehash
-hostprogs-$(CONFIG_PROM_CONSOLE) += conmakehash
-hostprogs-$(CONFIG_IKCONFIG) += bin2c
+hostprogs-$(CONFIG_KALLSYMS) += kallsyms
+hostprogs-$(CONFIG_LOGO) += pnmtologo
+hostprogs-$(CONFIG_VT) += conmakehash
+hostprogs-$(CONFIG_PROM_CONSOLE) += conmakehash
+hostprogs-$(CONFIG_IKCONFIG) += bin2c
+hostprogs-$(CONFIG_ELF_RELOCATABLE) += mketrel

always := $(hostprogs-y) $(hostprogs-m)

diff --git a/scripts/mketrel.c b/scripts/mketrel.c
new file mode 100644
index 0000000..effa312
--- /dev/null
+++ b/scripts/mketrel.c
@@ -0,0 +1,70 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <elf.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+static int fd;
+unsigned char e_ident[EI_NIDENT];
+
+void die(const char * str, ...)
+{
+ va_list args;
+ va_start(args, str);
+ vfprintf(stderr, str, args);
+ fputc('\n', stderr);
+ exit(1);
+}
+
+void file_open(const char *name)
+{
+ if ((fd = open(name, O_RDWR, 0)) < 0)
+ die("Unable to open `%s': %m", name);
+}
+
+static void mketrel(void)
+{
+ unsigned char e_type[2];
+ if (read(fd, &e_ident, sizeof(e_ident)) != sizeof(e_ident))
+ die("Cannot read ELF header: %s\n", strerror(errno));
+
+ if (memcmp(e_ident, ELFMAG, 4) != 0)
+ die("No ELF magic\n");
+
+ if ((e_ident[EI_CLASS] != ELFCLASS64) &&
+ (e_ident[EI_CLASS] != ELFCLASS32))
+ die("Unrecognized ELF class: %x\n", e_ident[EI_CLASS]);
+
+ if ((e_ident[EI_DATA] != ELFDATA2LSB) &&
+ (e_ident[EI_DATA] != ELFDATA2MSB))
+ die("Unrecognized ELF data encoding: %x\n", e_ident[EI_DATA]);
+
+ if (e_ident[EI_VERSION] != EV_CURRENT)
+ die("Unknown ELF version: %d\n", e_ident[EI_VERSION]);
+
+ if (e_ident[EI_DATA] == ELFDATA2LSB) {
+ e_type[0] = ET_REL & 0xff;
+ e_type[1] = ET_REL >> 8;
+ } else {
+ e_type[1] = ET_REL & 0xff;
+ e_type[0] = ET_REL >> 8;
+ }
+
+ if (write(fd, &e_type, sizeof(e_type)) != sizeof(e_type))
+ die("Cannot write ELF type: %s\n", strerror(errno));
+}
+
+int main(int argc, char **argv)
+{
+ if (argc != 2)
+ die("Usage: mketrel: vmlinux");
+ file_open(argv[1]);
+ mketrel();
+ close(fd);
+ return 0;
+}
--
1.5.1.1.181.g2de0