ARM: decompressor: fix BSS size calculation
Assuming size(1) gives the size of the BSS is a mistake - it reports the size of the .bss section in the ELF image, which may not be the same as the region we mark with the __bss_start..__bss_stop symbols. We use the size of the BSS in the decompressor to know whether the kernel will overwrite the appended dtb, by adding the BSS size to the size of the Image (stored at the end of the compressed data) and adding the desired address of the decompressed image. If the BSS size is smaller than it really is, the decompressor can incorrectly assume that the BSS clearance will not overwrite the DTB. Here is an illustration: $ arm-linux-size vmlinux text data bss dec hex filename 8136972 3098076 10240348 21475396 147b044 vmlinux $ arm-linux-nm vmlinux | grep __bss_ c0ac0e34 B __bss_start c1484f9c B __bss_stop $ stat -c %s arch/arm/boot/Image 11243060 In the above case, we are 12 bytes short. This is caused by the BSS section being aligned by one of its input sections: Idx Name Size VMA LMA File off Algn 23 __bug_table 00005d3c c0abb0f8 c0abb0f8 00acb0f8 2**2 CONTENTS, ALLOC, LOAD, DATA 24 .bss 009c415c c0ac0e40 c0ac0e40 00ad0e34 2**6 ALLOC Note that there's an additional 12 bytes difference between the file offset and LMA compared with the bug table - this occurs because one of the input sections for the .bss section requires a 64 byte alignment. Fix this by using 'nm' and perl to obtain the address of the __bss_start and __bss_stop symbols, using their difference for the size of the BSS. Tested-by: Tony Lindgren <tony@atomide.com> Tested-by: Keerthy <j-keerthy@ti.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
parent
99cf8f9031
commit
429f7a062e
|
@ -116,8 +116,11 @@ ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
|
|||
asflags-y := -DZIMAGE
|
||||
|
||||
# Supply kernel BSS size to the decompressor via a linker symbol.
|
||||
KBSS_SZ = $(shell $(CROSS_COMPILE)size $(obj)/../../../../vmlinux | \
|
||||
awk 'END{print $$3}')
|
||||
KBSS_SZ = $(shell $(CROSS_COMPILE)nm $(obj)/../../../../vmlinux | \
|
||||
perl -e 'while (<>) { \
|
||||
$$bss_start=hex($$1) if /^([[:xdigit:]]+) B __bss_start$$/; \
|
||||
$$bss_end=hex($$1) if /^([[:xdigit:]]+) B __bss_stop$$/; \
|
||||
}; printf "%d\n", $$bss_end - $$bss_start;')
|
||||
LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ)
|
||||
# Supply ZRELADDR to the decompressor via a linker symbol.
|
||||
ifneq ($(CONFIG_AUTO_ZRELADDR),y)
|
||||
|
|
Loading…
Reference in New Issue