[PATCH v3 05/19] x86, boot: Fix run_size calculation

[Baoquan He <bhe@redhat.com>]

From: Yinghai Lu <yinghai@kernel.org>

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+0x012c8000+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 <eternal.n08@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
v2->v3:
    Adjust the patch log.

 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 7a65a8a..42e76c2 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