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Subject[PATCH x86 for review II] [1/39] i386: move startup_32() in text.head section
Date

From: Vivek Goyal <vgoyal@in.ibm.com>

o Entry startup_32 was in .text section but it was accessing some init
data too and it prompts MODPOST to generate compilation warnings.

WARNING: vmlinux - Section mismatch: reference to .init.data:boot_params from
.text between '_text' (at offset 0xc0100029) and 'startup_32_smp'
WARNING: vmlinux - Section mismatch: reference to .init.data:boot_params from
.text between '_text' (at offset 0xc0100037) and 'startup_32_smp'
WARNING: vmlinux - Section mismatch: reference to
.init.data:init_pg_tables_end from .text between '_text' (at offset
0xc0100099) and 'startup_32_smp'

o Can't move startup_32 to .init.text as this entry point has to be at the
start of bzImage. Hence moved startup_32 to a new section .text.head and
instructed MODPOST to not to generate warnings if init data is being
accessed from .text.head section. This code has been audited.

o SMP boot up code (startup_32_smp) can go into .init.text if CPU hotplug
is not supported. Otherwise it generates more warnings

WARNING: vmlinux - Section mismatch: reference to .init.data:new_cpu_data from
.text between 'checkCPUtype' (at offset 0xc0100126) and 'is486'
WARNING: vmlinux - Section mismatch: reference to .init.data:new_cpu_data from
.text between 'checkCPUtype' (at offset 0xc0100130) and 'is486'

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/i386/kernel/head.S | 17 ++++++++++++++---
arch/i386/kernel/vmlinux.lds.S | 7 ++++++-
scripts/mod/modpost.c | 10 +++++++++-
3 files changed, 29 insertions(+), 5 deletions(-)
Index: linux/arch/i386/kernel/head.S
===================================================================
--- linux.orig/arch/i386/kernel/head.S
+++ linux/arch/i386/kernel/head.S
@@ -53,6 +53,7 @@
* any particular GDT layout, because we load our own as soon as we
* can.
*/
+.section .text.head,"ax",@progbits
ENTRY(startup_32)

#ifdef CONFIG_PARAVIRT
@@ -141,16 +142,25 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
jb 10b
movl %edi,(init_pg_tables_end - __PAGE_OFFSET)

-#ifdef CONFIG_SMP
xorl %ebx,%ebx /* This is the boot CPU (BSP) */
jmp 3f
-
/*
* Non-boot CPU entry point; entered from trampoline.S
* We can't lgdt here, because lgdt itself uses a data segment, but
* we know the trampoline has already loaded the boot_gdt_table GDT
* for us.
+ *
+ * If cpu hotplug is not supported then this code can go in init section
+ * which will be freed later
*/
+
+#ifdef CONFIG_HOTPLUG_CPU
+.section .text,"ax",@progbits
+#else
+.section .init.text,"ax",@progbits
+#endif
+
+#ifdef CONFIG_SMP
ENTRY(startup_32_smp)
cld
movl $(__BOOT_DS),%eax
@@ -208,8 +218,8 @@ ENTRY(startup_32_smp)
xorl %ebx,%ebx
incl %ebx

-3:
#endif /* CONFIG_SMP */
+3:

/*
* Enable paging
@@ -492,6 +502,7 @@ ignore_int:
#endif
iret

+.section .text
#ifdef CONFIG_PARAVIRT
startup_paravirt:
cld
Index: linux/arch/i386/kernel/vmlinux.lds.S
===================================================================
--- linux.orig/arch/i386/kernel/vmlinux.lds.S
+++ linux/arch/i386/kernel/vmlinux.lds.S
@@ -37,9 +37,14 @@ SECTIONS
{
. = LOAD_OFFSET + LOAD_PHYSICAL_ADDR;
phys_startup_32 = startup_32 - LOAD_OFFSET;
+
+ .text.head : AT(ADDR(.text.head) - LOAD_OFFSET) {
+ _text = .; /* Text and read-only data */
+ *(.text.head)
+ } :text = 0x9090
+
/* read-only */
.text : AT(ADDR(.text) - LOAD_OFFSET) {
- _text = .; /* Text and read-only data */
*(.text)
SCHED_TEXT
LOCK_TEXT
Index: linux/scripts/mod/modpost.c
===================================================================
--- linux.orig/scripts/mod/modpost.c
+++ linux/scripts/mod/modpost.c
@@ -641,12 +641,20 @@ static int secref_whitelist(const char *
if (f1 && f2)
return 1;

- /* Whitelist all references from .pci_fixup section if vmlinux */
+ /* Whitelist all references from .pci_fixup section if vmlinux
+ * Whitelist all refereces from .text.head to .init.data if vmlinux
+ * Whitelist all refereces from .text.head to .init.text if vmlinux
+ */
if (is_vmlinux(modname)) {
if ((strcmp(fromsec, ".pci_fixup") == 0) &&
(strcmp(tosec, ".init.text") == 0))
return 1;

+ if ((strcmp(fromsec, ".text.head") == 0) &&
+ ((strcmp(tosec, ".init.data") == 0) ||
+ (strcmp(tosec, ".init.text") == 0)))
+ return 1;
+
/* Check for pattern 3 */
for (s = pat3refsym; *s; s++)
if (strcmp(refsymname, *s) == 0)
-
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