[PATCH v8 11/28] x86/asm/head: annotate data appropriatelly
Use the new SYM_DATA, SYM_DATA_START, and SYM_DATA_END in both 32 and 64
bit heads. In the 64-bit version, define also
SYM_DATA_START_PAGE_ALIGNED locally using the new SYM_START. It is used
in the code instead of NEXT_PAGE() which was defined in this file and
has been using the obsolete macro GLOBAL().
Now, the data in the 64-bit object file look sane:
Value Size TypeBind Vis Ndx Name
4096 OBJECT GLOBAL DEFAULT 15 init_level4_pgt
1000 4096 OBJECT GLOBAL DEFAULT 15 level3_kernel_pgt
2000 2048 OBJECT GLOBAL DEFAULT 15 level2_kernel_pgt
3000 4096 OBJECT GLOBAL DEFAULT 15 level2_fixmap_pgt
4000 4096 OBJECT GLOBAL DEFAULT 15 level1_fixmap_pgt
5000 2 OBJECT GLOBAL DEFAULT 15 early_gdt_descr
5002 8 OBJECT LOCAL DEFAULT 15 early_gdt_descr_base
500a 8 OBJECT GLOBAL DEFAULT 15 phys_base
8 OBJECT GLOBAL DEFAULT 17 initial_code
0008 8 OBJECT GLOBAL DEFAULT 17 initial_gs
0010 8 OBJECT GLOBAL DEFAULT 17 initial_stack
4 OBJECT GLOBAL DEFAULT 19 early_recursion_flag
1000 4096 OBJECT GLOBAL DEFAULT 19 early_level4_pgt
2000 0x4 OBJECT GLOBAL DEFAULT 19 early_dynamic_pgts
4096 OBJECT GLOBAL DEFAULT 22 empty_zero_page
All have correct size and type.
Note, that we can now see that it might be worth pushing
early_recursion_flag after early_dynamic_pgts -- we are wasting almost
4K of .init.data.
Signed-off-by: Jiri Slaby
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: "H. Peter Anvin"
Cc: x...@kernel.org
---
arch/x86/kernel/head_32.S | 29 ---
arch/x86/kernel/head_64.S | 78 +--
2 files changed, 58 insertions(+), 49 deletions(-)
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 0bae769b7b59..2d5390d84467 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -502,8 +502,7 @@ ENDPROC(early_ignore_irq)
__INITDATA
.align 4
-GLOBAL(early_recursion_flag)
- .long 0
+SYM_DATA(early_recursion_flag, .long 0)
__REFDATA
.align 4
@@ -551,7 +550,7 @@ EXPORT_SYMBOL(empty_zero_page)
__PAGE_ALIGNED_DATA
/* Page-aligned for the benefit of paravirt? */
.align PGD_ALIGN
-ENTRY(initial_page_table)
+SYM_DATA_START(initial_page_table)
.long pa(initial_pg_pmd+PGD_IDENT_ATTR),0 /* low identity map */
# if KPMDS == 3
.long pa(initial_pg_pmd+PGD_IDENT_ATTR),0
@@ -569,17 +568,18 @@ ENTRY(initial_page_table)
# error "Kernel PMDs should be 1, 2 or 3"
# endif
.align PAGE_SIZE/* needs to be page-sized too */
+SYM_DATA_END(initial_page_table)
#endif
.data
.balign 4
-ENTRY(initial_stack)
- /*
-* The SIZEOF_PTREGS gap is a convention which helps the in-kernel
-* unwinder reliably detect the end of the stack.
-*/
- .long init_thread_union + THREAD_SIZE - SIZEOF_PTREGS - \
- TOP_OF_KERNEL_STACK_PADDING;
+/*
+ * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
+ * reliably detect the end of the stack.
+ */
+SYM_DATA(initial_stack,
+ .long init_thread_union + THREAD_SIZE -
+ SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING)
__INITRODATA
int_msg:
@@ -600,22 +600,25 @@ int_msg:
ALIGN
# early boot GDT descriptor (must use 1:1 address mapping)
.word 0 # 32 bit align gdt_desc.address
-boot_gdt_descr:
+SYM_DATA_START(boot_gdt_descr)
.word __BOOT_DS+7
.long boot_gdt - __PAGE_OFFSET
+SYM_DATA_END(boot_gdt_descr)
# boot GDT descriptor (later on used by CPU#0):
.word 0 # 32 bit align gdt_desc.address
-ENTRY(early_gdt_descr)
+SYM_DATA_START(early_gdt_descr)
.word GDT_ENTRIES*8-1
.long gdt_page /* Overwritten for secondary CPUs */
+SYM_DATA_END(early_gdt_descr)
/*
* The boot_gdt must mirror the equivalent in setup.S and is
* used only for booting.
*/
.align L1_CACHE_BYTES
-ENTRY(boot_gdt)
+SYM_DATA_START(boot_gdt)
.fill GDT_ENTRY_BOOT_CS,8,0
.quad 0x00cf9a00/* kernel 4GB code at 0x */
.quad 0x00cf9200/* kernel 4GB data at 0x */
+SYM_DATA_END(boot_gdt)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 6fedcda37634..6661c76a2049 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -260,16 +260,14 @@ END(start_cpu0)
/* Both SMP bootup and ACPI suspend change these variables */
__REFDATA
.balign 8
- GLOBAL(initial_code)
- .quad x86_64_start_kernel
- GLOBAL(initial_gs)
- .quad INIT_PER_CPU_VAR(fixed_percpu_data)
- GLOBAL(initial_stack)
- /*
-* The SIZEOF_PTREGS gap is a convention which helps the in-kernel
-* unwinder reliably detect the end of the stack.
-*/
- .quad init_thread_union + THREAD_SIZE - S
Re: [PATCH v8 11/28] x86/asm/head: annotate data appropriatelly
> Subject: Re: [PATCH v8 11/28] x86/asm/head: annotate data appropriatelly appropriately On Thu, Aug 08, 2019 at 12:38:37PM +0200, Jiri Slaby wrote: > Use the new SYM_DATA, SYM_DATA_START, and SYM_DATA_END in both 32 and 64 > bit heads. In the 64-bit version, define also > SYM_DATA_START_PAGE_ALIGNED locally using the new SYM_START. It is used > in the code instead of NEXT_PAGE() which was defined in this file and > has been using the obsolete macro GLOBAL(). > > Now, the data in the 64-bit object file look sane: > Value Size TypeBind Vis Ndx Name > 4096 OBJECT GLOBAL DEFAULT 15 init_level4_pgt > 1000 4096 OBJECT GLOBAL DEFAULT 15 level3_kernel_pgt > 2000 2048 OBJECT GLOBAL DEFAULT 15 level2_kernel_pgt > 3000 4096 OBJECT GLOBAL DEFAULT 15 level2_fixmap_pgt > 4000 4096 OBJECT GLOBAL DEFAULT 15 level1_fixmap_pgt > 5000 2 OBJECT GLOBAL DEFAULT 15 early_gdt_descr > 5002 8 OBJECT LOCAL DEFAULT 15 early_gdt_descr_base > 500a 8 OBJECT GLOBAL DEFAULT 15 phys_base > 8 OBJECT GLOBAL DEFAULT 17 initial_code > 0008 8 OBJECT GLOBAL DEFAULT 17 initial_gs > 0010 8 OBJECT GLOBAL DEFAULT 17 initial_stack > 4 OBJECT GLOBAL DEFAULT 19 early_recursion_flag > 1000 4096 OBJECT GLOBAL DEFAULT 19 early_level4_pgt > 2000 0x4 OBJECT GLOBAL DEFAULT 19 early_dynamic_pgts > 4096 OBJECT GLOBAL DEFAULT 22 empty_zero_page > > All have correct size and type. Nice. > > Note, that we can now see that it might be worth pushing > early_recursion_flag after early_dynamic_pgts -- we are wasting almost > 4K of .init.data. Yes, please do in a separate patch which can even go separately. I get here: --- Disassembly of section .init.data: 82684000 : ... 82685000 : ... 82686000 : ... 826c6000 : ... 826c6020 : --- vs --- Disassembly of section .init.data: 82684000 : ... 82685000 : ... 826c5000 : 826c5000: 00 00 add%al,(%rax) ... 826c5004 : ... 826c5020 : --- That's exactly 4K saved. > Signed-off-by: Jiri Slaby > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: x...@kernel.org > --- > arch/x86/kernel/head_32.S | 29 --- > arch/x86/kernel/head_64.S | 78 +-- > 2 files changed, 58 insertions(+), 49 deletions(-) > > diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S > index 0bae769b7b59..2d5390d84467 100644 > --- a/arch/x86/kernel/head_32.S > +++ b/arch/x86/kernel/head_32.S > @@ -502,8 +502,7 @@ ENDPROC(early_ignore_irq) > > __INITDATA > .align 4 > -GLOBAL(early_recursion_flag) > - .long 0 > +SYM_DATA(early_recursion_flag, .long 0) > > __REFDATA > .align 4 > @@ -551,7 +550,7 @@ EXPORT_SYMBOL(empty_zero_page) > __PAGE_ALIGNED_DATA > /* Page-aligned for the benefit of paravirt? */ > .align PGD_ALIGN > -ENTRY(initial_page_table) > +SYM_DATA_START(initial_page_table) > .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0 /* low identity map */ > # if KPMDS == 3 > .long pa(initial_pg_pmd+PGD_IDENT_ATTR),0 > @@ -569,17 +568,18 @@ ENTRY(initial_page_table) > # error "Kernel PMDs should be 1, 2 or 3" > # endif > .align PAGE_SIZE/* needs to be page-sized too */ > +SYM_DATA_END(initial_page_table) > #endif > > .data > .balign 4 > -ENTRY(initial_stack) > - /* > - * The SIZEOF_PTREGS gap is a convention which helps the in-kernel > - * unwinder reliably detect the end of the stack. > - */ > - .long init_thread_union + THREAD_SIZE - SIZEOF_PTREGS - \ > - TOP_OF_KERNEL_STACK_PADDING; > +/* > + * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder > + * reliably detect the end of the stack. > + */ > +SYM_DATA(initial_stack, > + .long init_thread_union + THREAD_SIZE - > + SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING) > > __INITRODATA > int_msg: > @@ -600,22 +600,25 @@ int_msg: > ALIGN > # early boot GDT descriptor (must use 1:1 address mapping) > .word 0 # 32 bit align gdt_desc.address > -boot_gdt_descr: > +SYM_DATA_START(boot_gdt_descr) > .word __BOOT_DS+7 > .long boot_gdt - __PAGE_OFFSET > +SYM_DATA_END(boot_gdt_descr) So there's one "globl boot_gdt_descr" above already and this turns into: .data .globl boot_gdt_descr ^ .align 4,0x90 # early boot GDT descriptor (must use 1:1 add
