[PATCH v4 03/20] x86, boot: Move compressed kernel to end of buffer before decompressing
From: Baoquan He
Date: Tue Mar 22 2016 - 03:33:09 EST
From: Yinghai Lu <yinghai@xxxxxxxxxx>
For better understanding clarify what are VO and ZO firstly. They are
introduced in below commits by hpa.
77d1a49 x86, boot: make symbols from the main vmlinux available
37ba7ab x86, boot: make kernel_alignment adjustable; new bzImage fields
VO:
- uncompressed kernel
- size: VO__end - VO__text
ZO:
- boot/compressed/vmlinux
- head text + compressed (VO+relocs) + decompressor code
- size: ZO__end - ZO_startup_32
And also copy INIT_SIZE definition here for reference. From below macros
we can see INIT_SIZE is either bigger than VO_INIT_SIZE or equal to
VO_INIT_SIZE.
#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
Current code uses extract_offset to decide the copied ZO position, it
put ZO starting from extract_offset. When INIT_SIZE is bigger than
VO_INIT_SIZE copied ZO occupies space from extract_offset to the end
of decompressing buffer, just like below.
0 extract_offset init_size
|-----------|---------------|------------------------|---------|
| | | |
VO__text startup_32 of ZO VO__end ZO__end
However when INIT_SIZE is equal to VO_INIT_SIZE there's still space left
from end of ZO to the end of decompressing buffer, like below.
0 extract_offset init_size
|-----------|---------------|------------------------|---------|
| | | |
VO__text startup_32 of ZO ZO__end VO__end
It's better to always put ZO right in the end of decompressing buffer.
Anyway, who doesn't like it to be better.
So in this patch add BP_init_size into asm-offsets.c to make it visible
to asm modules. And find the starting position of copied ZO by init_size
and ZO run size, namely (ZO__end - startup_32) when move ZO.
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
v2->v3:
Adjust the patch log.
arch/x86/boot/compressed/head_32.S | 11 +++++++++--
arch/x86/boot/compressed/head_64.S | 8 ++++++--
arch/x86/boot/compressed/mkpiggy.c | 3 ---
arch/x86/boot/compressed/vmlinux.lds.S | 1 +
arch/x86/kernel/asm-offsets.c | 1 +
arch/x86/kernel/vmlinux.lds.S | 1 +
6 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 8ef964d..0c140f9 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -148,7 +148,9 @@ preferred_addr:
1:
/* Target address to relocate to for decompression */
- addl $z_extract_offset, %ebx
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ addl %eax, %ebx
/* Set up the stack */
leal boot_stack_end(%ebx), %esp
@@ -210,8 +212,13 @@ relocated:
/* 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 */
- leal z_extract_offset_negative(%ebx), %ebp
+
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ movl %ebx, %ebp
+ subl %eax, %ebp
pushl %ebp /* output address */
+
pushl $z_input_len /* input_len */
leal input_data(%ebx), %eax
pushl %eax /* input_data */
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index b0c0d16..67dd8d3 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -102,7 +102,9 @@ ENTRY(startup_32)
1:
/* Target address to relocate to for decompression */
- addl $z_extract_offset, %ebx
+ movl BP_init_size(%esi), %eax
+ subl $_end, %eax
+ addl %eax, %ebx
/*
* Prepare for entering 64 bit mode
@@ -330,7 +332,9 @@ preferred_addr:
1:
/* Target address to relocate to for decompression */
- leaq z_extract_offset(%rbp), %rbx
+ movl BP_init_size(%rsi), %ebx
+ subl $_end, %ebx
+ addq %rbp, %rbx
/* Set up the stack */
leaq boot_stack_end(%rbx), %rsp
diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
index d8222f2..b980046 100644
--- a/arch/x86/boot/compressed/mkpiggy.c
+++ b/arch/x86/boot/compressed/mkpiggy.c
@@ -85,9 +85,6 @@ int main(int argc, char *argv[])
printf("z_output_len = %lu\n", (unsigned long)olen);
printf(".globl z_extract_offset\n");
printf("z_extract_offset = 0x%lx\n", offs);
- /* 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);
diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 34d047c..e24e0a0 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -70,5 +70,6 @@ SECTIONS
_epgtable = . ;
}
#endif
+ . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */
_end = .;
}
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 84a7524..506de14 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -81,6 +81,7 @@ void common(void) {
OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
OFFSET(BP_version, boot_params, hdr.version);
OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
+ OFFSET(BP_init_size, boot_params, hdr.init_size);
OFFSET(BP_pref_address, boot_params, hdr.pref_address);
OFFSET(BP_code32_start, boot_params, hdr.code32_start);
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index fe133b7..b8081e6 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -322,6 +322,7 @@ SECTIONS
__brk_limit = .;
}
+ . = ALIGN(PAGE_SIZE); /* keep VO_INIT_SIZE page aligned */
_end = .;
STABS_DEBUG
--
2.5.0