Re: [PATCH v4 07/20] x86, kaslr: Clean up useless code related to run_size.

From: Kees Cook
Date: Tue Mar 22 2016 - 16:52:33 EST

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In reply to: Baoquan He: "[PATCH v4 07/20] x86, kaslr: Clean up useless code related to run_size."
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On Tue, Mar 22, 2016 at 12:32 AM, Baoquan He <bhe@xxxxxxxxxx> wrote:
> From: Yinghai Lu <yinghai@xxxxxxxxxx>
>
> So now we use the formula below to get run_size.
>
> run_size = VO__end - VO__text
>
> Let's remove code for old run_size calculation and clean up the places
> where run_size need be passed in and out.
>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Cc: Junjie Mao <eternal.n08@xxxxxxxxx>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
> v2->v3:
> Adjust the patch log.
> v3->v4:
> Kees suggested that change run_size as const in decompress_kernel()
>
> arch/x86/boot/compressed/Makefile | 4 +---
> arch/x86/boot/compressed/head_32.S | 3 +--
> arch/x86/boot/compressed/head_64.S | 3 ---
> arch/x86/boot/compressed/misc.c | 6 ++----
> arch/x86/boot/compressed/mkpiggy.c | 10 ++-------
> arch/x86/tools/calc_run_size.sh | 42 --------------------------------------
> 6 files changed, 6 insertions(+), 62 deletions(-)
> delete mode 100644 arch/x86/tools/calc_run_size.sh
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index d9dedd9..fef80fa 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -105,10 +105,8 @@ 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 0c140f9..122b32f 100644
> --- a/arch/x86/boot/compressed/head_32.S
> +++ b/arch/x86/boot/compressed/head_32.S
> @@ -210,7 +210,6 @@ 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 */
>
> movl BP_init_size(%esi), %eax
> @@ -226,7 +225,7 @@ 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 67dd8d3..3691451 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -407,8 +407,6 @@ 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 */
> @@ -416,7 +414,6 @@ relocated:
> movq %rbp, %r8 /* output target address */
> movq $z_output_len, %r9 /* decompressed length, end of relocs */
> 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 4d317b7..def6207 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -393,9 +393,9 @@ 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)
> {
> + const unsigned long run_size = VO__end - VO__text;
> unsigned char *output_orig = output;
>
> real_mode = rmode;
> @@ -416,8 +416,6 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
> lines = real_mode->screen_info.orig_video_lines;
> cols = real_mode->screen_info.orig_video_cols;
>
> - run_size = VO__end - VO__text;
> -
> console_init();
> debug_putstr("early console in decompress_kernel\n");
>
> diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
> index a613c84..c5148642 100644
> --- a/arch/x86/boot/compressed/mkpiggy.c
> +++ b/arch/x86/boot/compressed/mkpiggy.c
> @@ -34,13 +34,11 @@ int main(int argc, char *argv[])
> {
> uint32_t olen;
> long ilen;
> - 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;
> }
>
> @@ -65,15 +63,11 @@ int main(int argc, char *argv[])
> ilen = ftell(f);
> olen = get_unaligned_le32(&olen);
>
> - run_size = atoi(argv[2]);
> -
> printf(".section \".rodata..compressed\",\"a\",@progbits\n");
> printf(".globl z_input_len\n");
> printf("z_input_len = %lu\n", ilen);
> printf(".globl z_output_len\n");
> printf("z_output_len = %lu\n", (unsigned long)olen);
> - 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
> --
> 2.5.0
>

--
Kees Cook
Chrome OS & Brillo Security

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In reply to: Baoquan He: "[PATCH v4 07/20] x86, kaslr: Clean up useless code related to run_size."
Next in thread: Baoquan He: "[PATCH v4 08/20] x86, kaslr: Get correct max_addr for relocs pointer"
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