On Tue, Mar 22, 2016 at 12:32 AM, Baoquan He <[email protected]> wrote: > From: Yinghai Lu <[email protected]> > > Firstly, current run_size is calculated via shell script > arch/x86/tools/calc_run_size.sh. It gets file offset and mem size of section > .bss and .brk in vmlinux, then add them as follows: > > run_size=$(( $offsetA + $sizeA + $sizeB )) > > However this is completely wrong. The offset is the starting address of > section or segment in elf file. Below is a vmlinux I compiled: > > [bhe@x1 linux]$ objdump -h vmlinux > > vmlinux: file format elf64-x86-64 > > Sections: > Idx Name Size VMA LMA File off Algn > 27 .bss 00170000 ffffffff81ec8000 0000000001ec8000 012c8000 > 2**12 > ALLOC > 28 .brk 00027000 ffffffff82038000 0000000002038000 012c8000 2**0 > ALLOC > > Here we can get run_size is 0x145f000. > 0x012c8000 + 0x00170000 + 0x00027000 = 0x145f000 > > [bhe@x1 linux]$ readelf -l vmlinux > > Elf file type is EXEC (Executable file) > Entry point 0x1000000 > There are 5 program headers, starting at offset 64 > > Program Headers: > Type Offset VirtAddr PhysAddr > FileSiz MemSiz Flags Align > LOAD 0x0000000000200000 0xffffffff81000000 0x0000000001000000 > 0x0000000000b5e000 0x0000000000b5e000 R E 200000 > LOAD 0x0000000000e00000 0xffffffff81c00000 0x0000000001c00000 > 0x0000000000145000 0x0000000000145000 RW 200000 > LOAD 0x0000000001000000 0x0000000000000000 0x0000000001d45000 > 0x0000000000018158 0x0000000000018158 RW 200000 > LOAD 0x000000000115e000 0xffffffff81d5e000 0x0000000001d5e000 > 0x000000000016a000 0x0000000000301000 RWE 200000 > NOTE 0x000000000099bcac 0xffffffff8179bcac 0x000000000179bcac > 0x00000000000001bc 0x00000000000001bc 4 > > Section to Segment mapping: > Segment Sections... > 00 .text .notes __ex_table .rodata __bug_table .pci_fixup .tracedata > __ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata __param __modver > 01 .data .vvar > 02 .data..percpu > 03 .init.text .init.data .x86_cpu_dev.init .parainstructions > .altinstructions .altinstr_replacement .iommu_table .apicdrivers .exit.text > .smp_locks .bss .brk > 04 .notes > > Here we can get the same value as current run_size if we add p_offset > and p_memsz. > 0x000000000115e000 + 0x0000000000301000 = 0x145f000 > > But is it right? Obviously not. We should calculate it using the last LOAD > program segment like this: > run_size = phdr->p_paddr + phdr->p_memsz - physical load addr of kernel > run_size = 0x0000000001d5e000 + 0x0000000000301000 - 0x0000000001000000 = > 0x105f000 > > It's equal to VO_end-VO_text and certainly it's simpler to do. > _end: 0xffffffff8205f000 > _text:0xffffffff81000000 > run_size = 0xffffffff8205f000 - 0xffffffff81000000 = 0x105f000 > > Secondly run_size is a simple constant, we don't need to pass it around > and we already have voffset.h for that. We can share voffset.h between > misc.c and header.S instead of getting run_size in other ways. Hence in > this patch, we move voffset.h creation code to boot/compressed/Makefile. > > Dependence was: > boot/header.S ==> boot/voffset.h ==> vmlinux > boot/header.S ==> compressed/vmlinux ==> compressed/misc.c > Now become: > boot/header.S ==> compressed/vmlinux ==> compressed/misc.c ==> boot/voffset.h > ==> vmlinux > > Use macro in misc.c to replace passed run_size. > > Fixes: e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") > Cc: Junjie Mao <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Josh Triplett <[email protected]> > Cc: Andrew Morton <[email protected]> > Signed-off-by: Yinghai Lu <[email protected]> > Signed-off-by: Baoquan He <[email protected]>
Thanks for spending the time to convince me on this. :) Acked-by: Kees Cook <[email protected]> -Kees > --- > v2->v3: > Adjust the patch log. > v3->v4: > Correct calculation errors in patch log that Kees pointed out. > > arch/x86/boot/Makefile | 11 +---------- > arch/x86/boot/compressed/Makefile | 12 ++++++++++++ > arch/x86/boot/compressed/misc.c | 3 +++ > 3 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile > index bd021e5..40f0ae2 100644 > --- a/arch/x86/boot/Makefile > +++ b/arch/x86/boot/Makefile > @@ -78,15 +78,6 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE > > SETUP_OBJS = $(addprefix $(obj)/,$(setup-y)) > > -sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] > \(_text\|_end\)$$/\#define VO_\2 0x\1/p' > - > -quiet_cmd_voffset = VOFFSET $@ > - cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@ > - > -targets += voffset.h > -$(obj)/voffset.h: vmlinux FORCE > - $(call if_changed,voffset) > - > sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] > \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|_ehead\|_text\|z_.*\)$$/\#define > ZO_\2 0x\1/p' > > quiet_cmd_zoffset = ZOFFSET $@ > @@ -98,7 +89,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE > > > AFLAGS_header.o += -I$(obj) > -$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h > +$(obj)/header.o: $(obj)/zoffset.h > > LDFLAGS_setup.elf := -T > $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE > diff --git a/arch/x86/boot/compressed/Makefile > b/arch/x86/boot/compressed/Makefile > index f9ce75d..d9dedd9 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -41,6 +41,18 @@ LDFLAGS_vmlinux := -T > hostprogs-y := mkpiggy > HOST_EXTRACFLAGS += -I$(srctree)/tools/include > > +sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] > \(_text\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' > + > +quiet_cmd_voffset = VOFFSET $@ > + cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@ > + > +targets += ../voffset.h > + > +$(obj)/../voffset.h: vmlinux FORCE > + $(call if_changed,voffset) > + > +$(obj)/misc.o: $(obj)/../voffset.h > + > vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \ > $(obj)/string.o $(obj)/cmdline.o \ > $(obj)/piggy.o $(obj)/cpuflags.o > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c > index e7c6fdf..4d317b7 100644 > --- a/arch/x86/boot/compressed/misc.c > +++ b/arch/x86/boot/compressed/misc.c > @@ -11,6 +11,7 @@ > > #include "misc.h" > #include "../string.h" > +#include "../voffset.h" > > /* WARNING!! > * This code is compiled with -fPIC and it is relocated dynamically > @@ -415,6 +416,8 @@ 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"); > > -- > 2.5.0 > -- Kees Cook Chrome OS & Brillo Security
