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s390/decompressor: rework uncompressed image info collection 

The kernel decompressor has to know several bits of information about
uncompressed image. Currently this info is collected by running "nm" on
uncompressed vmlinux + "sed" and producing sizes.h file. This method
worked well, but it has several disadvantages. Obscure symbols name
pattern matching is fragile. Adding new values makes pattern even
longer. Logic is spread across code and make file. Limited ability to
adjust symbols values (currently magic lma value of 0x100000 is always
subtracted). Apart from that same pieces of information (and more)
would be needed for early memory detection and features like KASLR
outside of boot/compressed/ folder where sizes.h is generated.

To overcome limitations new "struct vmlinux_info" has been introduced
to include values needed for the decompressor and the rest of the
boot code. The only static instance of vmlinux_info is produced during
vmlinux link step by filling in struct fields by the linker (like it is
done with input_data in boot/compressed/vmlinux.scr.lds.S). This way
individual values could be adjusted with all the knowledge linker has
and arithmetic it supports. Later .vmlinux.info section (which contains
struct vmlinux_info) is transplanted into the decompressor image and
dropped from uncompressed image altogether.

While doing that replace "compressed/vmlinux.scr.lds.S" linker
script (whose purpose is to rename .data section in piggy.o to
.rodata.compressed) with plain objcopy command. And simplify
decompressor's linker script.

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Vasily Gorbik 2018-07-19 16:51:25 +02:00 committed by Martin Schwidefsky
parent 8f75582a2f
commit 369f91c374
7 changed files with 61 additions and 56 deletions
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33
arch/s390/boot/compressed/Makefile
View File

@ -9,13 +9,14 @@ KCOV_INSTRUMENT := n
GCOV_PROFILE := n
UBSAN_SANITIZE := n
obj-y := $(if $(CONFIG_KERNEL_UNCOMPRESSED),,misc.o) piggy.o
obj-y := $(if $(CONFIG_KERNEL_UNCOMPRESSED),,misc.o) piggy.o info.o
targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
targets += vmlinux.scr.lds $(obj-y) $(if $(CONFIG_KERNEL_UNCOMPRESSED),,sizes.h)
targets += info.bin $(obj-y)
KBUILD_AFLAGS := $(KBUILD_AFLAGS_DECOMPRESSOR)
KBUILD_CFLAGS := $(KBUILD_CFLAGS_DECOMPRESSOR)
OBJCOPYFLAGS :=
OBJECTS := $(addprefix $(obj)/,$(obj-y))
@ -23,20 +24,16 @@ LDFLAGS_vmlinux := --oformat $(LD_BFD) -e startup -T
$(obj)/vmlinux: $(obj)/vmlinux.lds $(objtree)/arch/s390/boot/startup.a $(OBJECTS)
$(call if_changed,ld)
# extract required uncompressed vmlinux symbols and adjust them to reflect offsets inside vmlinux.bin
sed-sizes := -e 's/^\([0-9a-fA-F]*\) . \(__bss_start\|_end\)$$/\#define SZ\2 (0x\1 - 0x100000)/p'
OBJCOPYFLAGS_info.bin := -O binary --only-section=.vmlinux.info
$(obj)/info.bin: vmlinux FORCE
$(call if_changed,objcopy)
quiet_cmd_sizes = GEN $@
cmd_sizes = $(NM) $< | sed -n $(sed-sizes) > $@
OBJCOPYFLAGS_info.o := -I binary -O elf64-s390 -B s390:64-bit --rename-section .data=.vmlinux.info
$(obj)/info.o: $(obj)/info.bin FORCE
$(call if_changed,objcopy)
$(obj)/sizes.h: vmlinux
$(call if_changed,sizes)
CFLAGS_misc.o += -I$(objtree)/$(obj)
$(obj)/misc.o: $(obj)/sizes.h
OBJCOPYFLAGS_vmlinux.bin := -R .comment -S
$(obj)/vmlinux.bin: vmlinux
OBJCOPYFLAGS_vmlinux.bin := -O binary --remove-section=.comment --remove-section=.vmlinux.info -S
$(obj)/vmlinux.bin: vmlinux FORCE
$(call if_changed,objcopy)
vmlinux.bin.all-y := $(obj)/vmlinux.bin
@ -61,10 +58,10 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y)
$(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y)
$(call if_changed,xzkern)
LDFLAGS_piggy.o := -r --format binary --oformat $(LD_BFD) -T
$(obj)/piggy.o: $(obj)/vmlinux.scr.lds $(obj)/vmlinux.bin$(suffix-y)
$(call if_changed,ld)
OBJCOPYFLAGS_piggy.o := -I binary -O elf64-s390 -B s390:64-bit --rename-section .data=.vmlinux.bin.compressed
$(obj)/piggy.o: $(obj)/vmlinux.bin$(suffix-y) FORCE
$(call if_changed,objcopy)
chkbss := $(filter-out $(obj)/misc.o $(obj)/piggy.o,$(OBJECTS))
chkbss := $(filter-out $(obj)/misc.o $(obj)/piggy.o $(obj)/info.o,$(OBJECTS))
chkbss-target := $(obj)/vmlinux.bin
include $(srctree)/arch/s390/scripts/Makefile.chkbss

13
arch/s390/boot/compressed/decompressor.h
View File

@ -3,9 +3,18 @@
#define BOOT_COMPRESSED_DECOMPRESSOR_H
#ifdef CONFIG_KERNEL_UNCOMPRESSED
static inline void *decompress_kernel(unsigned long *uncompressed_size) {}
static inline void *decompress_kernel(void) {}
#else
void *decompress_kernel(unsigned long *uncompressed_size);
void *decompress_kernel(void);
#endif
struct vmlinux_info {
unsigned long default_lma;
void (*entry)(void);
unsigned long image_size; /* does not include .bss */
};
extern char _vmlinux_info[];
#define vmlinux (*(struct vmlinux_info *)_vmlinux_info)
#endif /* BOOT_COMPRESSED_DECOMPRESSOR_H */

15
arch/s390/boot/compressed/misc.c
View File

@ -11,7 +11,6 @@
#include <asm/page.h>
#include <asm/sclp.h>
#include <asm/ipl.h>
#include "sizes.h"
#include "decompressor.h"
/*
@ -26,10 +25,10 @@
#define memzero(s, n) memset((s), 0, (n))
/* Symbols defined by linker scripts */
extern char input_data[];
extern int input_len;
extern char _end[];
extern char _bss[], _ebss[];
extern unsigned char _compressed_start[];
extern unsigned char _compressed_end[];
static void error(char *m);
@ -83,12 +82,12 @@ static void error(char *x)
asm volatile("lpsw %0" : : "Q" (psw));
}
void *decompress_kernel(unsigned long *uncompressed_size)
void *decompress_kernel(void)
{
void *output, *kernel_end;
output = (void *) ALIGN((unsigned long) _end + HEAP_SIZE, PAGE_SIZE);
kernel_end = output + SZ__bss_start;
kernel_end = output + vmlinux.image_size;
#ifdef CONFIG_BLK_DEV_INITRD
/*
@ -111,9 +110,7 @@ void *decompress_kernel(unsigned long *uncompressed_size)
free_mem_ptr = (unsigned long) _end;
free_mem_end_ptr = free_mem_ptr + HEAP_SIZE;
__decompress(input_data, input_len, NULL, NULL, output, 0, NULL, error);
if (uncompressed_size)
*uncompressed_size = SZ__bss_start;
__decompress(_compressed_start, _compressed_end - _compressed_start,
NULL, NULL, output, 0, NULL, error);
return output;
}

21
arch/s390/boot/compressed/vmlinux.lds.S
View File

@ -8,9 +8,6 @@ ENTRY(startup)
SECTIONS
{
/* Be careful parts of head_64.S assume startup_32 is at
* address 0.
*/
. = 0;
.head.text : {
_head = . ;
@ -26,7 +23,7 @@ SECTIONS
.rodata : {
_rodata = . ;
*(.rodata) /* read-only data */
*(EXCLUDE_FILE (*piggy.o) .rodata.compressed)
*(.rodata.*)
_erodata = . ;
}
.data : {
@ -35,14 +32,26 @@ SECTIONS
*(.data.*)
_edata = . ;
}
startup_continue = 0x100000;
/*
* uncompressed image info used by the decompressor it should match
* struct vmlinux_info. It comes from .vmlinux.info section of
* uncompressed vmlinux in a form of info.o
*/
. = ALIGN(8);
.vmlinux.info : {
_vmlinux_info = .;
*(.vmlinux.info)
}
#ifdef CONFIG_KERNEL_UNCOMPRESSED
. = 0x100000;
#else
. = ALIGN(8);
#endif
.rodata.compressed : {
*(.rodata.compressed)
_compressed_start = .;
*(.vmlinux.bin.compressed)
_compressed_end = .;
}
. = ALIGN(256);
.bss : {

15
arch/s390/boot/compressed/vmlinux.scr.lds.S
View File

@ -1,15 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
SECTIONS
{
.rodata.compressed : {
#ifndef CONFIG_KERNEL_UNCOMPRESSED
input_len = .;
LONG(input_data_end - input_data) input_data = .;
#endif
*(.data)
#ifndef CONFIG_KERNEL_UNCOMPRESSED
output_len = . - 4;
input_data_end = .;
#endif
}
}

10
arch/s390/boot/startup.c
View File

@ -5,13 +5,11 @@
void startup_kernel(void)
{
void (*startup_continue)(void) = (void *)0x100000;
unsigned long uncompressed_size;
void *uncompressed_img;
void *img;
if (!IS_ENABLED(CONFIG_KERNEL_UNCOMPRESSED)) {
uncompressed_img = decompress_kernel(&uncompressed_size);
memmove(startup_continue, uncompressed_img, uncompressed_size);
img = decompress_kernel();
memmove((void *)vmlinux.default_lma, img, vmlinux.image_size);
}
startup_continue();
vmlinux.entry();
}

10
arch/s390/kernel/vmlinux.lds.S
View File

@ -146,6 +146,16 @@ SECTIONS
_end = . ;
/*
* uncompressed image info used by the decompressor
* it should match struct vmlinux_info
*/
.vmlinux.info 0 : {
QUAD(_stext) /* default_lma */
QUAD(startup_continue) /* entry */
QUAD(__bss_start - _stext) /* image_size */
}
/* Debugging sections. */
STABS_DEBUG
DWARF_DEBUG