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Subject[PATCH 2/2] x86_64: Remove CONFIG_PHYSICAL_START and CONFIG_RELOCATABLE
Date

Now that the vmlinux is marked as relocatable there is no reason to
retain the CONFIG_PHYSICAL_START option, as we can put the binary we
have at any 2MB aligned address in memory.

With CONFIG_PHYSICAL_START gone the handful of code lines that depend
on CONFIG_RELOCATABLE no longer make sense to be conditional and can
be removed.

The big win of this patch (besides Kconfig simplicity) is that the
nasty BUILD_BUG_ON test for people misaligning their kernel when using
CONFIG_PHYSICAL_START can be removed as this case can only happen with
CONFIG_PHYSICAL_START selected.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
arch/x86_64/Kconfig | 55 +-----------------------------------
arch/x86_64/Makefile | 2 -
arch/x86_64/boot/compressed/head.S | 13 +--------
arch/x86_64/boot/setup.S | 4 --
arch/x86_64/defconfig | 2 -
arch/x86_64/kernel/head64.c | 7 ----
include/asm-x86_64/page.h | 2 +-
7 files changed, 3 insertions(+), 82 deletions(-)
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 773b487..713c1ad 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -565,62 +565,9 @@ config CRASH_DUMP
which are loaded in the main kernel with kexec-tools into
a specially reserved region and then later executed after
a crash by kdump/kexec. The crash dump kernel must be compiled
- to a memory address not used by the main kernel or BIOS using
- PHYSICAL_START.
+ to a memory address not used by the main kernel or BIOS
For more details see Documentation/kdump/kdump.txt

-config RELOCATABLE
- bool "Build a relocatable kernel(EXPERIMENTAL)"
- depends on EXPERIMENTAL
- help
- Builds a relocatable kernel. This enables loading and running
- a kernel binary from a different physical address than it has
- been compiled for.
-
- One use is for the kexec on panic case where the recovery kernel
- must live at a different physical address than the primary
- kernel.
-
- Note: If CONFIG_RELOCATABLE=y, then kernel run from the address
- it has been loaded at and compile time physical address
- (CONFIG_PHYSICAL_START) is ignored.
-
-config PHYSICAL_START
- hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)
- default "0x200000"
- help
- This gives the physical address where the kernel is loaded. It
- should be aligned to 2MB boundary.
-
- If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
- bzImage will decompress itself to above physical address and
- run from there. Otherwise, bzImage will run from the address where
- it has been loaded by the boot loader and will ignore above physical
- address.
-
- In normal kdump cases one does not have to set/change this option
- as now bzImage can be compiled as a completely relocatable image
- (CONFIG_RELOCATABLE=y) and be used to load and run from a different
- address. This option is mainly useful for the folks who don't want
- to use a bzImage for capturing the crash dump and want to use a
- vmlinux instead.
-
- So if you are using bzImage for capturing the crash dump, leave
- the value here unchanged to 0x200000 and set CONFIG_RELOCATABLE=y.
- Otherwise if you plan to use vmlinux for capturing the crash dump
- change this value to start of the reserved region (Typically 16MB
- 0x1000000). In other words, it can be set based on the "X" value as
- specified in the "crashkernel=YM@XM" command line boot parameter
- passed to the panic-ed kernel. Typically this parameter is set as
- crashkernel=64M@16M. Please take a look at
- Documentation/kdump/kdump.txt for more details about crash dumps.
-
- Usage of bzImage for capturing the crash dump is advantageous as
- one does not have to build two kernels. Same kernel can be used
- as production kernel and capture kernel.
-
- Don't change this unless you know what you are doing.
-
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
depends on PROC_FS
diff --git a/arch/x86_64/Makefile b/arch/x86_64/Makefile
index 5ae79ab..5d96f4f 100644
--- a/arch/x86_64/Makefile
+++ b/arch/x86_64/Makefile
@@ -124,7 +124,6 @@ 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) \
@@ -132,7 +131,6 @@ define cmd_vmlinux__
$(filter-out $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) FORCE ,$^) \
&& scripts/mketrel $@
endef
-endif

CLEAN_FILES += arch/$(ARCH)/boot/fdimage \
arch/$(ARCH)/boot/image.iso \
diff --git a/arch/x86_64/boot/compressed/head.S b/arch/x86_64/boot/compressed/head.S
index f9d5692..493723e 100644
--- a/arch/x86_64/boot/compressed/head.S
+++ b/arch/x86_64/boot/compressed/head.S
@@ -71,13 +71,9 @@ startup_32:
* for safe in-place decompression.
*/

-#ifdef CONFIG_RELOCATABLE
movl %ebp, %ebx
addl $(LARGE_PAGE_SIZE -1), %ebx
andl $LARGE_PAGE_MASK, %ebx
-#else
- movl $CONFIG_PHYSICAL_START, %ebx
-#endif

/* Replace the compressed data size with the uncompressed size */
subl input_len(%ebp), %ebx
@@ -200,21 +196,14 @@ ENTRY(startup_64)
* we were loaded at aligned to a 2M boundary. %rbp contains the
* decompressed kernel start address.
*
- * If it is a relocatable kernel then decompress and run the kernel
- * from load address aligned to 2MB addr, otherwise decompress and
- * run the kernel from CONFIG_PHYSICAL_START
+ * Decompress and run the kernel from load address aligned to 2MB addr
*/

/* Start with the delta to where the kernel will run at. */
-#ifdef CONFIG_RELOCATABLE
leaq startup_32(%rip) /* - $startup_32 */, %rbp
addq $(LARGE_PAGE_SIZE - 1), %rbp
andq $LARGE_PAGE_MASK, %rbp
movq %rbp, %rbx
-#else
- movq $CONFIG_PHYSICAL_START, %rbp
- movq %rbp, %rbx
-#endif

/* Replace the compressed data size with the uncompressed size */
movl input_len(%rip), %eax
diff --git a/arch/x86_64/boot/setup.S b/arch/x86_64/boot/setup.S
index 4f88510..8a70c92 100644
--- a/arch/x86_64/boot/setup.S
+++ b/arch/x86_64/boot/setup.S
@@ -158,11 +158,7 @@ cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
ramdisk_max: .long 0xffffffff
kernel_alignment: .long 0x200000 # physical addr alignment required for
# protected mode relocatable kernel
-#ifdef CONFIG_RELOCATABLE
relocatable_kernel: .byte 1
-#else
-relocatable_kernel: .byte 0
-#endif
pad2: .byte 0
pad3: .word 0

diff --git a/arch/x86_64/defconfig b/arch/x86_64/defconfig
index 90c5a9d..d977bcb 100644
--- a/arch/x86_64/defconfig
+++ b/arch/x86_64/defconfig
@@ -174,8 +174,6 @@ CONFIG_X86_MCE_INTEL=y
CONFIG_X86_MCE_AMD=y
# CONFIG_KEXEC is not set
# CONFIG_CRASH_DUMP is not set
-# CONFIG_RELOCATABLE is not set
-CONFIG_PHYSICAL_START=0x200000
CONFIG_SECCOMP=y
# CONFIG_CC_STACKPROTECTOR is not set
# CONFIG_HZ_100 is not set
diff --git a/arch/x86_64/kernel/head64.c b/arch/x86_64/kernel/head64.c
index 213d90e..6c34bdd 100644
--- a/arch/x86_64/kernel/head64.c
+++ b/arch/x86_64/kernel/head64.c
@@ -62,13 +62,6 @@ void __init x86_64_start_kernel(char * real_mode_data)
{
int i;

- /*
- * Make sure kernel is aligned to 2MB address. Catching it at compile
- * time is better. Change your config file and compile the kernel
- * for a 2MB aligned address (CONFIG_PHYSICAL_START)
- */
- BUILD_BUG_ON(CONFIG_PHYSICAL_START & (__KERNEL_ALIGN - 1));
-
/* clear bss before set_intr_gate with early_idt_handler */
clear_bss();

diff --git a/include/asm-x86_64/page.h b/include/asm-x86_64/page.h
index 7bb725f..20662ab 100644
--- a/include/asm-x86_64/page.h
+++ b/include/asm-x86_64/page.h
@@ -78,7 +78,7 @@ extern unsigned long phys_base;

#endif /* !__ASSEMBLY__ */

-#define __PHYSICAL_START CONFIG_PHYSICAL_START
+#define __PHYSICAL_START 0x200000
#define __KERNEL_ALIGN 0x200000
#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START)
#define __START_KERNEL_map 0xffffffff80000000
--
1.5.1.1.181.g2de0
-
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