| Message ID | 1425456048-16236-2-git-send-email-yinghai@kernel.org |
|---|---|
| State | Not Applicable |
| Headers | show |
On Wed, Mar 04, 2015 at 12:00:34AM -0800, Yinghai Lu wrote: > commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") > > introduced one run_size for kaslr. > > We do not need to have home grown run_size. > > We should use real runtime size (include copy/decompress) aka init_size Why? I can see why but you need to explain it here. Also, look at the e6023367d779 commit message. Now this is how you do a commit message! Especially if it is early boot code, you explain stuff. Junjie even went the distance and did a nice graphic. So please redo your commit message. And saying it is trivial and obvious will not get you anywhere, as you've noticed already.
On Fri, Mar 6, 2015 at 5:55 AM, Borislav Petkov <bp@alien8.de> wrote: > On Wed, Mar 04, 2015 at 12:00:34AM -0800, Yinghai Lu wrote: >> commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") >> >> introduced one run_size for kaslr. >> >> We do not need to have home grown run_size. >> >> We should use real runtime size (include copy/decompress) aka init_size > > Why? New change log: Subject: [PATCH] x86, kaslr: Use init_size instead of run_size commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") introduced one run_size for kaslr. We should use real runtime size (include copy/decompress) aka init_size. run_size is size of VO (vmlinux). init_size is the size needed for decompress and it is bigger than run_size when decompress need more buff. According to arch/x86/boot/header.S: | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) | #define VO_INIT_SIZE (VO__end - VO__text) | #if ZO_INIT_SIZE > VO_INIT_SIZE | #define INIT_SIZE ZO_INIT_SIZE | #else | #define INIT_SIZE VO_INIT_SIZE | #endif | init_size: .long INIT_SIZE # kernel initialization size Bootloader allocate buffer according to init_size in hdr, and load the ZO (arch/x86/boot/compressed/vmlinux) from start of that buffer. During running of ZO, ZO move itself to the middle of buffer at z_extract_offset to make sure that decompressor would not have output overwrite input data before input data get consumed. But z_extract_offset calculating is based on size of VO (vmlinux) and size of compressed VO only at first. So need to make [z_extra_offset, init_size) will fit ZO, that means init_size need to be adjusted according to ZO size. That make init_size is always >= run_size. During aslr buffer searching, we need to make sure the buffer is bigger enough for decompress at first. So use init_size instead, and kill not needed run_size related code. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Mar 6, 2015 at 10:44 AM, Yinghai Lu <yinghai@kernel.org> wrote: > On Fri, Mar 6, 2015 at 5:55 AM, Borislav Petkov <bp@alien8.de> wrote: >> On Wed, Mar 04, 2015 at 12:00:34AM -0800, Yinghai Lu wrote: >>> commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") >>> >>> introduced one run_size for kaslr. >>> >>> We do not need to have home grown run_size. >>> >>> We should use real runtime size (include copy/decompress) aka init_size >> >> Why? > > New change log: > > Subject: [PATCH] x86, kaslr: Use init_size instead of run_size > > commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") > introduced one run_size for kaslr. > We should use real runtime size (include copy/decompress) aka init_size. > > run_size is size of VO (vmlinux). > init_size is the size needed for decompress and it is bigger than run_size > when decompress need more buff. > > According to arch/x86/boot/header.S: > | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) > | #define VO_INIT_SIZE (VO__end - VO__text) > | #if ZO_INIT_SIZE > VO_INIT_SIZE > | #define INIT_SIZE ZO_INIT_SIZE > | #else > | #define INIT_SIZE VO_INIT_SIZE > | #endif > | init_size: .long INIT_SIZE # kernel initialization size > > Bootloader allocate buffer according to init_size in hdr, and load the > ZO (arch/x86/boot/compressed/vmlinux) from start of that buffer. > During running of ZO, ZO move itself to the middle of buffer at > z_extract_offset to make sure that decompressor would not have output > overwrite input data before input data get consumed. > But z_extract_offset calculating is based on size of VO (vmlinux) and size > of compressed VO only at first. > So need to make [z_extra_offset, init_size) will fit ZO, that means > init_size need to be adjusted according to ZO size. > That make init_size is always >= run_size. > > During aslr buffer searching, we need to make sure the buffer is bigger > enough for decompress at first. So use init_size instead, and kill not > needed run_size related code. I don't see how bss and brk are related to these sizes. Can you explain how bss, brk, and initrd factor into these sizes? Those were what run_size was created to represent. I don't want to accidentally start stomping on bss and brk again. :) -Kees
On Fri, Mar 6, 2015 at 10:55 AM, Kees Cook <keescook@chromium.org> wrote: > On Fri, Mar 6, 2015 at 10:44 AM, Yinghai Lu <yinghai@kernel.org> wrote: > > I don't see how bss and brk are related to these sizes. Can you > explain how bss, brk, and initrd factor into these sizes? Those were > what run_size was created to represent. I don't want to accidentally > start stomping on bss and brk again. :) VO (vlinux) init size aka VO_INIT_SIZE already inlude that. Please check update version. commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") introduced one run_size for kaslr. We should use real runtime size (include copy/decompress) aka init_size. run_size is VO (vmlinux) init size include bss and brk. init_size is the size needed for decompress and it is bigger than run_size when decompress need more buff. According to arch/x86/boot/header.S: | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) | #define VO_INIT_SIZE (VO__end - VO__text) | #if ZO_INIT_SIZE > VO_INIT_SIZE | #define INIT_SIZE ZO_INIT_SIZE | #else | #define INIT_SIZE VO_INIT_SIZE | #endif | init_size: .long INIT_SIZE # kernel initialization size Bootloader allocate buffer according to init_size in hdr, and load the ZO (arch/x86/boot/compressed/vmlinux) from start of that buffer. init_size first should come from VO (vmlinux) init size. That VO init size is from VO _end to VO _end and include VO bss and brk area. During running of ZO, ZO move itself to the middle of buffer at z_extract_offset to make sure that decompressor would not have output overwrite input data before input data get consumed. But z_extract_offset calculating is based on size of VO (vmlinux) and size of compressed VO only at first. So need to make sure [z_extra_offset, init_size) will fit ZO, that means init_size need to be adjusted according to ZO size. That make init_size is always >= run_size. During aslr buffer searching, we need to make sure the buffer is bigger enough for decompress at first. So use init_size instead, and kill not needed run_size related code. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Mar 6, 2015 at 11:28 AM, Yinghai Lu <yinghai@kernel.org> wrote: > On Fri, Mar 6, 2015 at 10:55 AM, Kees Cook <keescook@chromium.org> wrote: >> On Fri, Mar 6, 2015 at 10:44 AM, Yinghai Lu <yinghai@kernel.org> wrote: > >> >> I don't see how bss and brk are related to these sizes. Can you >> explain how bss, brk, and initrd factor into these sizes? Those were >> what run_size was created to represent. I don't want to accidentally >> start stomping on bss and brk again. :) > > VO (vlinux) init size aka VO_INIT_SIZE already inlude that. > > Please check update version. > > > commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") > introduced one run_size for kaslr. > We should use real runtime size (include copy/decompress) aka init_size. > > run_size is VO (vmlinux) init size include bss and brk. > init_size is the size needed for decompress and it is bigger than run_size > when decompress need more buff. > > According to arch/x86/boot/header.S: > | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) > | #define VO_INIT_SIZE (VO__end - VO__text) > | #if ZO_INIT_SIZE > VO_INIT_SIZE > | #define INIT_SIZE ZO_INIT_SIZE > | #else > | #define INIT_SIZE VO_INIT_SIZE > | #endif > | init_size: .long INIT_SIZE # kernel initialization size Okay, I've proven this to myself now. :) I think it would be valuable to call out that brk and bss are included in the _end calculation. For others: $ objdump -h vmlinux | egrep '\.(bss|brk)' 25 .bss 00da7000 ffffffff82436000 0000000002436000 01836000 2**12 26 .brk 00026000 ffffffff831dd000 00000000031dd000 01836000 2**0 $ nm vmlinux | egrep ' _(text|end)' ffffffff83203000 B _end ffffffff81000000 T _text $ objdump -h vmlinux | bash arch/x86/tools/calc_run_size.sh 39858176 $ bc obase=16 39858176 2603000 ibase=16 81000000 + 2603000 83603000 So, _end - _text does equal _text + bss offset + bss size + brk size Thanks! It'll be nice to lose the run_size hack. Adding some documentation to the code here would help others in the future trying to find this value, I think. :) -Kees > > Bootloader allocate buffer according to init_size in hdr, and load the > ZO (arch/x86/boot/compressed/vmlinux) from start of that buffer. > init_size first should come from VO (vmlinux) init size. That VO init size > is from VO _end to VO _end and include VO bss and brk area. > > During running of ZO, ZO move itself to the middle of buffer at > z_extract_offset to make sure that decompressor would not have output > overwrite input data before input data get consumed. > But z_extract_offset calculating is based on size of VO (vmlinux) and size > of compressed VO only at first. > So need to make sure [z_extra_offset, init_size) will fit ZO, that means > init_size need to be adjusted according to ZO size. > That make init_size is always >= run_size. > > During aslr buffer searching, we need to make sure the buffer is bigger > enough for decompress at first. So use init_size instead, and kill not > needed run_size related code.
On Fri, Mar 6, 2015 at 11:56 AM, Kees Cook <keescook@chromium.org> wrote: > On Fri, Mar 6, 2015 at 11:28 AM, Yinghai Lu <yinghai@kernel.org> wrote: > Okay, I've proven this to myself now. :) I think it would be valuable > to call out that brk and bss are included in the _end calculation. For > others: ... > So, _end - _text does equal _text + bss offset + bss size + brk size > > Thanks! It'll be nice to lose the run_size hack. Adding some > documentation to the code here would help others in the future trying > to find this value, I think. :) in arch/x86/kernel/vmlinux.lds.S, we have /* BSS */ . = ALIGN(PAGE_SIZE); .bss : AT(ADDR(.bss) - LOAD_OFFSET) { __bss_start = .; *(.bss..page_aligned) *(.bss) . = ALIGN(PAGE_SIZE); __bss_stop = .; } . = ALIGN(PAGE_SIZE); .brk : AT(ADDR(.brk) - LOAD_OFFSET) { __brk_base = .; . += 64 * 1024; /* 64k alignment slop space */ *(.brk_reservation) /* areas brk users have reserved */ __brk_limit = .; } _end = .; so _end already cover bss and brk. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 0a291cd..70cc92c 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -92,10 +92,8 @@ suffix-$(CONFIG_KERNEL_XZ) := xz suffix-$(CONFIG_KERNEL_LZO) := lzo suffix-$(CONFIG_KERNEL_LZ4) := lz4 -RUN_SIZE = $(shell $(OBJDUMP) -h vmlinux | \ - $(CONFIG_SHELL) $(srctree)/arch/x86/tools/calc_run_size.sh) quiet_cmd_mkpiggy = MKPIGGY $@ - cmd_mkpiggy = $(obj)/mkpiggy $< $(RUN_SIZE) > $@ || ( rm -f $@ ; false ) + cmd_mkpiggy = $(obj)/mkpiggy $< > $@ || ( rm -f $@ ; false ) targets += piggy.S $(obj)/piggy.S: $(obj)/vmlinux.bin.$(suffix-y) $(obj)/mkpiggy FORCE diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 1d7fbbc..cbed140 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -207,8 +207,7 @@ relocated: * Do the decompression, and jump to the new kernel.. */ /* push arguments for decompress_kernel: */ - pushl $z_run_size /* size of kernel with .bss and .brk */ - pushl $z_output_len /* decompressed length, end of relocs */ + pushl $z_output_len /* decompressed length */ leal z_extract_offset_negative(%ebx), %ebp pushl %ebp /* output address */ pushl $z_input_len /* input_len */ @@ -218,7 +217,7 @@ relocated: pushl %eax /* heap area */ pushl %esi /* real mode pointer */ call decompress_kernel /* returns kernel location in %eax */ - addl $28, %esp + addl $24, %esp /* * Jump to the decompressed kernel. diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 6b1766c..2884e0c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -402,16 +402,13 @@ relocated: * Do the decompression, and jump to the new kernel.. */ pushq %rsi /* Save the real mode argument */ - movq $z_run_size, %r9 /* size of kernel with .bss and .brk */ - pushq %r9 movq %rsi, %rdi /* real mode address */ leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ leaq input_data(%rip), %rdx /* input_data */ movl $z_input_len, %ecx /* input_len */ movq %rbp, %r8 /* output target address */ - movq $z_output_len, %r9 /* decompressed length, end of relocs */ + movq $z_output_len, %r9 /* decompressed length */ call decompress_kernel /* returns kernel location in %rax */ - popq %r9 popq %rsi /* diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 5903089..51e9e54 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -370,10 +370,10 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, unsigned char *input_data, unsigned long input_len, unsigned char *output, - unsigned long output_len, - unsigned long run_size) + unsigned long output_len) { unsigned char *output_orig = output; + unsigned long init_size; real_mode = rmode; @@ -396,15 +396,14 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, free_mem_ptr = heap; /* Heap */ free_mem_end_ptr = heap + BOOT_HEAP_SIZE; + init_size = real_mode->hdr.init_size; + /* - * The memory hole needed for the kernel is the larger of either - * the entire decompressed kernel plus relocation table, or the - * entire decompressed kernel plus .bss and .brk sections. + * The memory hole needed for the kernel is init_size for running + * and init_size is bigger than output_len always. */ output = choose_kernel_location(real_mode, input_data, input_len, - output, - output_len > run_size ? output_len - : run_size); + output, init_size); /* Validate memory location choices. */ if ((unsigned long)output & (MIN_KERNEL_ALIGN - 1)) diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c index d8222f2..b669ab6 100644 --- a/arch/x86/boot/compressed/mkpiggy.c +++ b/arch/x86/boot/compressed/mkpiggy.c @@ -36,13 +36,11 @@ int main(int argc, char *argv[]) uint32_t olen; long ilen; unsigned long offs; - unsigned long run_size; FILE *f = NULL; int retval = 1; - if (argc < 3) { - fprintf(stderr, "Usage: %s compressed_file run_size\n", - argv[0]); + if (argc < 2) { + fprintf(stderr, "Usage: %s compressed_file\n", argv[0]); goto bail; } @@ -76,7 +74,6 @@ int main(int argc, char *argv[]) offs += olen >> 12; /* Add 8 bytes for each 32K block */ offs += 64*1024 + 128; /* Add 64K + 128 bytes slack */ offs = (offs+4095) & ~4095; /* Round to a 4K boundary */ - run_size = atoi(argv[2]); printf(".section \".rodata..compressed\",\"a\",@progbits\n"); printf(".globl z_input_len\n"); @@ -88,8 +85,6 @@ int main(int argc, char *argv[]) /* z_extract_offset_negative allows simplification of head_32.S */ printf(".globl z_extract_offset_negative\n"); printf("z_extract_offset_negative = -0x%lx\n", offs); - printf(".globl z_run_size\n"); - printf("z_run_size = %lu\n", run_size); printf(".globl input_data, input_data_end\n"); printf("input_data:\n"); diff --git a/arch/x86/tools/calc_run_size.sh b/arch/x86/tools/calc_run_size.sh deleted file mode 100644 index 1a4c17b..0000000 --- a/arch/x86/tools/calc_run_size.sh +++ /dev/null @@ -1,42 +0,0 @@ -#!/bin/sh -# -# Calculate the amount of space needed to run the kernel, including room for -# the .bss and .brk sections. -# -# Usage: -# objdump -h a.out | sh calc_run_size.sh - -NUM='\([0-9a-fA-F]*[ \t]*\)' -OUT=$(sed -n 's/^[ \t0-9]*.b[sr][sk][ \t]*'"$NUM$NUM$NUM$NUM"'.*/\1\4/p') -if [ -z "$OUT" ] ; then - echo "Never found .bss or .brk file offset" >&2 - exit 1 -fi - -OUT=$(echo ${OUT# }) -sizeA=$(printf "%d" 0x${OUT%% *}) -OUT=${OUT#* } -offsetA=$(printf "%d" 0x${OUT%% *}) -OUT=${OUT#* } -sizeB=$(printf "%d" 0x${OUT%% *}) -OUT=${OUT#* } -offsetB=$(printf "%d" 0x${OUT%% *}) - -run_size=$(( $offsetA + $sizeA + $sizeB )) - -# BFD linker shows the same file offset in ELF. -if [ "$offsetA" -ne "$offsetB" ] ; then - # Gold linker shows them as consecutive. - endB=$(( $offsetB + $sizeB )) - if [ "$endB" != "$run_size" ] ; then - printf "sizeA: 0x%x\n" $sizeA >&2 - printf "offsetA: 0x%x\n" $offsetA >&2 - printf "sizeB: 0x%x\n" $sizeB >&2 - printf "offsetB: 0x%x\n" $offsetB >&2 - echo ".bss and .brk are non-contiguous" >&2 - exit 1 - fi -fi - -printf "%d\n" $run_size -exit 0
commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") introduced one run_size for kaslr. We do not need to have home grown run_size. We should use real runtime size (include copy/decompress) aka init_size Please check arch/x86/boot/header.S about init_size for detail. Fixes: e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Matt Fleming <matt.fleming@intel.com> Cc: Kees Cook <keescook@chromium.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Junjie Mao <eternal.n08@gmail.com> Signed-off-by: Yinghai Lu <yinghai@kernel.org> --- arch/x86/boot/compressed/Makefile | 4 +--- arch/x86/boot/compressed/head_32.S | 5 ++--- arch/x86/boot/compressed/head_64.S | 5 +---- arch/x86/boot/compressed/misc.c | 15 +++++++------- arch/x86/boot/compressed/mkpiggy.c | 9 ++------ arch/x86/tools/calc_run_size.sh | 42 -------------------------------------- 6 files changed, 13 insertions(+), 67 deletions(-) delete mode 100644 arch/x86/tools/calc_run_size.sh