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Date:	Sat, 5 Feb 2011 00:34:06 GMT
From:	"tip-bot for H. Peter Anvin" <hpa@...ux.intel.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	castet.matthieu@...e.fr, kees.cook@...onical.com,
	tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/urgent] x86-32: Make sure the stack is set up before we use it

Commit-ID:  990957d4076354d449921b598cc8de28764cf7ed
Gitweb:     http://git.kernel.org/tip/990957d4076354d449921b598cc8de28764cf7ed
Author:     H. Peter Anvin <hpa@...ux.intel.com>
AuthorDate: Fri, 4 Feb 2011 16:14:11 -0800
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Fri, 4 Feb 2011 16:27:21 -0800

x86-32: Make sure the stack is set up before we use it

Since checkin ebba638ae723d8a8fc2f7abce5ec18b688b791d7 we call
verify_cpu even in 32-bit mode.  Unfortunately, calling a function
means using the stack, and the stack pointer was not initialized in
the 32-bit setup code!  This code initializes the stack pointer, and
simplifies the interface slightly since it is easier to rely on just a
pointer value rather than a descriptor; we need to have different
values for the segment register anyway.

This retains start_stack as a virtual address, even though a physical
address would be more convenient for 32 bits; the 64-bit code wants
the other way around...

Reported-by: Matthieu Castet <castet.matthieu@...e.fr>
LKML-Reference: <4D41E86D.8060205@...e.fr>
Cc: Kees Cook <kees.cook@...onical.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/include/asm/smp.h   |    5 +----
 arch/x86/kernel/acpi/sleep.c |    2 +-
 arch/x86/kernel/head_32.S    |   20 ++++++++++++--------
 arch/x86/kernel/head_64.S    |    1 -
 arch/x86/kernel/smpboot.c    |    4 ++--
 5 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 4c2f63c..1f46951 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -40,10 +40,7 @@ DECLARE_EARLY_PER_CPU(u16, x86_cpu_to_apicid);
 DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid);
 
 /* Static state in head.S used to set up a CPU */
-extern struct {
-	void *sp;
-	unsigned short ss;
-} stack_start;
+extern unsigned long stack_start; /* Initial stack pointer address */
 
 struct smp_ops {
 	void (*smp_prepare_boot_cpu)(void);
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 69fd72a..4d9ebba 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -100,7 +100,7 @@ int acpi_save_state_mem(void)
 #else /* CONFIG_64BIT */
 	header->trampoline_segment = setup_trampoline() >> 4;
 #ifdef CONFIG_SMP
-	stack_start.sp = temp_stack + sizeof(temp_stack);
+	stack_start = (unsigned long)temp_stack + sizeof(temp_stack);
 	early_gdt_descr.address =
 			(unsigned long)get_cpu_gdt_table(smp_processor_id());
 	initial_gs = per_cpu_offset(smp_processor_id());
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index fc293dc..10a6381 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -85,6 +85,8 @@ RESERVE_BRK(pagetables, INIT_MAP_SIZE)
  */
 __HEAD
 ENTRY(startup_32)
+	movl pa(stack_start),%ecx
+	
 	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
 		us to not reload segments */
 	testb $(1<<6), BP_loadflags(%esi)
@@ -99,7 +101,9 @@ ENTRY(startup_32)
 	movl %eax,%es
 	movl %eax,%fs
 	movl %eax,%gs
+	movl %eax,%ss
 2:
+	leal -__PAGE_OFFSET(%ecx),%esp
 
 /*
  * Clear BSS first so that there are no surprises...
@@ -145,8 +149,6 @@ ENTRY(startup_32)
  * _brk_end is set up to point to the first "safe" location.
  * Mappings are created both at virtual address 0 (identity mapping)
  * and PAGE_OFFSET for up to _end.
- *
- * Note that the stack is not yet set up!
  */
 #ifdef CONFIG_X86_PAE
 
@@ -282,6 +284,9 @@ ENTRY(startup_32_smp)
 	movl %eax,%es
 	movl %eax,%fs
 	movl %eax,%gs
+	movl pa(stack_start),%ecx
+	movl %eax,%ss
+	leal -__PAGE_OFFSET(%ecx),%esp
 #endif /* CONFIG_SMP */
 default_entry:
 
@@ -347,8 +352,8 @@ default_entry:
 	movl %eax,%cr0		/* ..and set paging (PG) bit */
 	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
 1:
-	/* Set up the stack pointer */
-	lss stack_start,%esp
+	/* Shift the stack pointer to a virtual address */
+	addl $__PAGE_OFFSET, %esp
 
 /*
  * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
@@ -475,7 +480,6 @@ is386:	movl $2,%ecx		# set MP
 	movb $1, ready
 	cmpb $0,%cl		# the first CPU calls start_kernel
 	je   1f
-	movl (stack_start), %esp
 1:
 #endif /* CONFIG_SMP */
 	jmp *(initial_code)
@@ -670,15 +674,15 @@ ENTRY(initial_page_table)
 #endif
 
 .data
+.balign 4
 ENTRY(stack_start)
 	.long init_thread_union+THREAD_SIZE
-	.long __BOOT_DS
-
-ready:	.byte 0
 
 early_recursion_flag:
 	.long 0
 
+ready:	.byte 0
+
 int_msg:
 	.asciz "Unknown interrupt or fault at: %p %p %p\n"
 
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 239046b..1ee8493 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -264,7 +264,6 @@ ENTRY(secondary_startup_64)
 
 	ENTRY(stack_start)
 	.quad  init_thread_union+THREAD_SIZE-8
-	.word  0
 	__FINITDATA
 
 bad_address:
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0cbe8c0..03273b6 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -638,7 +638,7 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
 	 * target processor state.
 	 */
 	startup_ipi_hook(phys_apicid, (unsigned long) start_secondary,
-			 (unsigned long)stack_start.sp);
+			 stack_start);
 
 	/*
 	 * Run STARTUP IPI loop.
@@ -785,7 +785,7 @@ do_rest:
 #endif
 	early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
 	initial_code = (unsigned long)start_secondary;
-	stack_start.sp = (void *) c_idle.idle->thread.sp;
+	stack_start  = c_idle.idle->thread.sp;
 
 	/* start_ip had better be page-aligned! */
 	start_ip = setup_trampoline();
--
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