[PATCH v4 10/27] x86: head, annotate data appropriatelly

Jiri Slaby
2017-10-02T09:16:51Z

Use the new SYM_DATA_SIMPLE 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 Type Bind Vis Ndx Name
0000 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
0000 8 OBJECT GLOBAL DEFAULT 17 initial_code
0008 8 OBJECT GLOBAL DEFAULT 17 initial_gs
0010 8 OBJECT GLOBAL DEFAULT 17 initial_stack
0000 4 OBJECT GLOBAL DEFAULT 19 early_recursion_flag
1000 4096 OBJECT GLOBAL DEFAULT 19 early_level4_pgt
2000 0x40000 OBJECT GLOBAL DEFAULT 19 early_dynamic_pgts
0000 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 <jslaby@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
arch/x86/kernel/head_32.S | 28 ++++++++++---------
arch/x86/kernel/head_64.S | 70 +++++++++++++++++++++++++----------------------
2 files changed, 53 insertions(+), 45 deletions(-)

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index bcf07134a31e..5bf2a7fe2da7 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -504,8 +504,7 @@ ENDPROC(early_ignore_irq)

__INITDATA
.align 4
-GLOBAL(early_recursion_flag)
- .long 0
+SYM_DATA_SIMPLE(early_recursion_flag, .long 0)

__REFDATA
.align 4
@@ -543,7 +542,7 @@ EXPORT_SYMBOL(empty_zero_page)
__PAGE_ALIGNED_DATA
/* Page-aligned for the benefit of paravirt? */
.align PAGE_SIZE
-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
@@ -561,17 +560,17 @@ 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_SIMPLE(initial_stack, .long init_thread_union + THREAD_SIZE -
+ SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING)

__INITRODATA
int_msg:
@@ -592,22 +591,25 @@ 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 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
.quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
+SYM_DATA_END(boot_gdt)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index a2668b2ced90..f134b1f61256 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -257,16 +257,14 @@ ENDPROC(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(irq_stack_union)
- 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 - SIZEOF_PTREGS
+SYM_DATA_SIMPLE(initial_code, .quad x86_64_start_kernel)
+SYM_DATA_SIMPLE(initial_gs, .quad INIT_PER_CPU_VAR(irq_stack_union))
+/*
+ * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
+ * reliably detect the end of the stack.
+ */
+SYM_DATA_SIMPLE(initial_stack,
+ .quad init_thread_union + THREAD_SIZE - SIZEOF_PTREGS)
__FINITDATA

__INIT
@@ -335,12 +333,10 @@ SYM_CODE_END(early_idt_handler_common)
__INITDATA

.balign 4
-GLOBAL(early_recursion_flag)
- .long 0
+SYM_DATA_SIMPLE(early_recursion_flag, .long 0)

-#define NEXT_PAGE(name) \
- .balign PAGE_SIZE; \
-GLOBAL(name)
+#define SYM_DATA_START_PAGE_ALIGNED(name) \
+ SYM_START(name, SYM_V_GLOBAL, .balign PAGE_SIZE)

/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT) \
@@ -351,54 +347,62 @@ GLOBAL(name)
.endr

__INITDATA
-NEXT_PAGE(early_top_pgt)
+SYM_DATA_START_PAGE_ALIGNED(early_top_pgt)
.fill 511,8,0
#ifdef CONFIG_X86_5LEVEL
.quad level4_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
#else
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
#endif
+SYM_DATA_END(early_top_pgt)

-NEXT_PAGE(early_dynamic_pgts)
+SYM_DATA_START_PAGE_ALIGNED(early_dynamic_pgts)
.fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0
+SYM_DATA_END(early_dynamic_pgts)

.data

#ifndef CONFIG_XEN
-NEXT_PAGE(init_top_pgt)
+SYM_DATA_START_PAGE_ALIGNED(init_top_pgt)
.fill 512,8,0
+SYM_DATA_END(init_top_pgt)
#else
-NEXT_PAGE(init_top_pgt)
+SYM_DATA_START_PAGE_ALIGNED(init_top_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.org init_top_pgt + PGD_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.org init_top_pgt + PGD_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
+SYM_DATA_END(init_top_pgt)

-NEXT_PAGE(level3_ident_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.fill 511, 8, 0
-NEXT_PAGE(level2_ident_pgt)
+SYM_DATA_END(level3_ident_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level2_ident_pgt)
/* Since I easily can, map the first 1G.
* Don't set NX because code runs from these pages.
*/
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
+SYM_DATA_END(level2_ident_pgt)
#endif

#ifdef CONFIG_X86_5LEVEL
-NEXT_PAGE(level4_kernel_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level4_kernel_pgt)
.fill 511,8,0
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
+SYM_DATA_END(level4_kernel_pgt)
#endif

-NEXT_PAGE(level3_kernel_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
+SYM_DATA_END(level3_kernel_pgt)

-NEXT_PAGE(level2_kernel_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level2_kernel_pgt)
/*
* 512 MB kernel mapping. We spend a full page on this pagetable
* anyway.
@@ -411,25 +415,26 @@ NEXT_PAGE(level2_kernel_pgt)
*/
PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
KERNEL_IMAGE_SIZE/PMD_SIZE)
+SYM_DATA_END(level2_kernel_pgt)

-NEXT_PAGE(level2_fixmap_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level2_fixmap_pgt)
.fill 506,8,0
.quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
.fill 5,8,0
+SYM_DATA_END(level2_fixmap_pgt)

-NEXT_PAGE(level1_fixmap_pgt)
+SYM_DATA_START_PAGE_ALIGNED(level1_fixmap_pgt)
.fill 512,8,0
+SYM_DATA_END(level1_fixmap_pgt)

#undef PMDS

.data
.align 16
- .globl early_gdt_descr
-early_gdt_descr:
- .word GDT_ENTRIES*8-1
-early_gdt_descr_base:
- .quad INIT_PER_CPU_VAR(gdt_page)
+
+SYM_DATA_SIMPLE(early_gdt_descr, .word GDT_ENTRIES*8-1)
+SYM_DATA_SIMPLE_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page))

/* This must match the first entry in level2_kernel_pgt */
SYM_DATA_SIMPLE(phys_base, .quad 0x0000000000000000)
@@ -438,7 +443,8 @@ EXPORT_SYMBOL(phys_base)
#include "../../x86/xen/xen-head.S"

__PAGE_ALIGNED_BSS
-NEXT_PAGE(empty_zero_page)
+SYM_DATA_START_PAGE_ALIGNED(empty_zero_page)
.skip PAGE_SIZE
+SYM_DATA_END(empty_zero_page)
EXPORT_SYMBOL(empty_zero_page)

--
2.14.2