[PATCH 2/3] linux 2.6.18 merge: eliminate Xen specials: alternative.c

["Jan Beulich" <jbeulich@novell.com>]

The sole (x86-64 specific) difference of arch/i386/kernel/alternative-xen.c
over its native original can be eliminated by slightly adjusting x86-64's
make_readonly(), and the Xen special can then be removed.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

Index: head-2007-02-27/arch/i386/kernel/alternative-xen.c
===================================================================
--- head-2007-02-27.orig/arch/i386/kernel/alternative-xen.c	2007-02-27 16:22:53.000000000 +0100
+++ /dev/null	1970-01-01 00:00:00.000000000 +0000
@@ -1,389 +0,0 @@
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <linux/list.h>
-#include <asm/alternative.h>
-#include <asm/sections.h>
-
-static int no_replacement    = 0;
-static int smp_alt_once      = 0;
-static int debug_alternative = 0;
-
-static int __init noreplacement_setup(char *s)
-{
-	no_replacement = 1;
-	return 1;
-}
-static int __init bootonly(char *str)
-{
-	smp_alt_once = 1;
-	return 1;
-}
-static int __init debug_alt(char *str)
-{
-	debug_alternative = 1;
-	return 1;
-}
-
-__setup("noreplacement", noreplacement_setup);
-__setup("smp-alt-boot", bootonly);
-__setup("debug-alternative", debug_alt);
-
-#define DPRINTK(fmt, args...) if (debug_alternative) \
-	printk(KERN_DEBUG fmt, args)
-
-#ifdef GENERIC_NOP1
-/* Use inline assembly to define this because the nops are defined
-   as inline assembly strings in the include files and we cannot
-   get them easily into strings. */
-asm("\t.data\nintelnops: "
-	GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
-	GENERIC_NOP7 GENERIC_NOP8);
-extern unsigned char intelnops[];
-static unsigned char *intel_nops[ASM_NOP_MAX+1] = {
-	NULL,
-	intelnops,
-	intelnops + 1,
-	intelnops + 1 + 2,
-	intelnops + 1 + 2 + 3,
-	intelnops + 1 + 2 + 3 + 4,
-	intelnops + 1 + 2 + 3 + 4 + 5,
-	intelnops + 1 + 2 + 3 + 4 + 5 + 6,
-	intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-};
-#endif
-
-#ifdef K8_NOP1
-asm("\t.data\nk8nops: "
-	K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
-	K8_NOP7 K8_NOP8);
-extern unsigned char k8nops[];
-static unsigned char *k8_nops[ASM_NOP_MAX+1] = {
-	NULL,
-	k8nops,
-	k8nops + 1,
-	k8nops + 1 + 2,
-	k8nops + 1 + 2 + 3,
-	k8nops + 1 + 2 + 3 + 4,
-	k8nops + 1 + 2 + 3 + 4 + 5,
-	k8nops + 1 + 2 + 3 + 4 + 5 + 6,
-	k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-};
-#endif
-
-#ifdef K7_NOP1
-asm("\t.data\nk7nops: "
-	K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
-	K7_NOP7 K7_NOP8);
-extern unsigned char k7nops[];
-static unsigned char *k7_nops[ASM_NOP_MAX+1] = {
-	NULL,
-	k7nops,
-	k7nops + 1,
-	k7nops + 1 + 2,
-	k7nops + 1 + 2 + 3,
-	k7nops + 1 + 2 + 3 + 4,
-	k7nops + 1 + 2 + 3 + 4 + 5,
-	k7nops + 1 + 2 + 3 + 4 + 5 + 6,
-	k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
-};
-#endif
-
-#ifdef CONFIG_X86_64
-
-extern char __vsyscall_0;
-static inline unsigned char** find_nop_table(void)
-{
-	return k8_nops;
-}
-
-#else /* CONFIG_X86_64 */
-
-static struct nop {
-	int cpuid;
-	unsigned char **noptable;
-} noptypes[] = {
-	{ X86_FEATURE_K8, k8_nops },
-	{ X86_FEATURE_K7, k7_nops },
-	{ -1, NULL }
-};
-
-static unsigned char** find_nop_table(void)
-{
-	unsigned char **noptable = intel_nops;
-	int i;
-
-	for (i = 0; noptypes[i].cpuid >= 0; i++) {
-		if (boot_cpu_has(noptypes[i].cpuid)) {
-			noptable = noptypes[i].noptable;
-			break;
-		}
-	}
-	return noptable;
-}
-
-#endif /* CONFIG_X86_64 */
-
-extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-extern struct alt_instr __smp_alt_instructions[], __smp_alt_instructions_end[];
-extern u8 *__smp_locks[], *__smp_locks_end[];
-
-extern u8 __smp_alt_begin[], __smp_alt_end[];
-
-/* Replace instructions with better alternatives for this CPU type.
-   This runs before SMP is initialized to avoid SMP problems with
-   self modifying code. This implies that assymetric systems where
-   APs have less capabilities than the boot processor are not handled.
-   Tough. Make sure you disable such features by hand. */
-
-void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
-{
-	unsigned char **noptable = find_nop_table();
-	struct alt_instr *a;
-	u8 *instr;
-	int diff, i, k;
-
-	DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
-	for (a = start; a < end; a++) {
-		BUG_ON(a->replacementlen > a->instrlen);
-		if (!boot_cpu_has(a->cpuid))
-			continue;
-		instr = a->instr;
-#ifdef CONFIG_X86_64
-		/* vsyscall code is not mapped yet. resolve it manually. */
-		if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
-			instr -= VSYSCALL_START - (unsigned long)&__vsyscall_0;
-			DPRINTK("%s: vsyscall fixup: %p => %p\n",
-				__FUNCTION__, a->instr, instr);
-		}
-#endif
-		memcpy(instr, a->replacement, a->replacementlen);
-		diff = a->instrlen - a->replacementlen;
-		/* Pad the rest with nops */
-		for (i = a->replacementlen; diff > 0; diff -= k, i += k) {
-			k = diff;
-			if (k > ASM_NOP_MAX)
-				k = ASM_NOP_MAX;
-			memcpy(a->instr + i, noptable[k], k);
-		}
-	}
-}
-
-#ifdef CONFIG_SMP
-
-static void alternatives_smp_save(struct alt_instr *start, struct alt_instr *end)
-{
-	struct alt_instr *a;
-
-	DPRINTK("%s: alt table %p-%p\n", __FUNCTION__, start, end);
-	for (a = start; a < end; a++) {
-		memcpy(a->replacement + a->replacementlen,
-		       a->instr,
-		       a->instrlen);
-	}
-}
-
-static void alternatives_smp_apply(struct alt_instr *start, struct alt_instr *end)
-{
-	struct alt_instr *a;
-
-	for (a = start; a < end; a++) {
-		memcpy(a->instr,
-		       a->replacement + a->replacementlen,
-		       a->instrlen);
-	}
-}
-
-static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
-{
-	u8 **ptr;
-
-	for (ptr = start; ptr < end; ptr++) {
-		if (*ptr < text)
-			continue;
-		if (*ptr > text_end)
-			continue;
-		**ptr = 0xf0; /* lock prefix */
-	};
-}
-
-static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
-{
-	unsigned char **noptable = find_nop_table();
-	u8 **ptr;
-
-	for (ptr = start; ptr < end; ptr++) {
-		if (*ptr < text)
-			continue;
-		if (*ptr > text_end)
-			continue;
-		**ptr = noptable[1][0];
-	};
-}
-
-struct smp_alt_module {
-	/* what is this ??? */
-	struct module	*mod;
-	char		*name;
-
-	/* ptrs to lock prefixes */
-	u8		**locks;
-	u8		**locks_end;
-
-	/* .text segment, needed to avoid patching init code ;) */
-	u8		*text;
-	u8		*text_end;
-
-	struct list_head next;
-};
-static LIST_HEAD(smp_alt_modules);
-static DEFINE_SPINLOCK(smp_alt);
-
-void alternatives_smp_module_add(struct module *mod, char *name,
-				 void *locks, void *locks_end,
-				 void *text,  void *text_end)
-{
-	struct smp_alt_module *smp;
-	unsigned long flags;
-
-	if (no_replacement)
-		return;
-
-	if (smp_alt_once) {
-		if (boot_cpu_has(X86_FEATURE_UP))
-			alternatives_smp_unlock(locks, locks_end,
-						text, text_end);
-		return;
-	}
-
-	smp = kzalloc(sizeof(*smp), GFP_KERNEL);
-	if (NULL == smp)
-		return; /* we'll run the (safe but slow) SMP code then ... */
-
-	smp->mod	= mod;
-	smp->name	= name;
-	smp->locks	= locks;
-	smp->locks_end	= locks_end;
-	smp->text	= text;
-	smp->text_end	= text_end;
-	DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n",
-		__FUNCTION__, smp->locks, smp->locks_end,
-		smp->text, smp->text_end, smp->name);
-
-	spin_lock_irqsave(&smp_alt, flags);
-	list_add_tail(&smp->next, &smp_alt_modules);
-	if (boot_cpu_has(X86_FEATURE_UP))
-		alternatives_smp_unlock(smp->locks, smp->locks_end,
-					smp->text, smp->text_end);
-	spin_unlock_irqrestore(&smp_alt, flags);
-}
-
-void alternatives_smp_module_del(struct module *mod)
-{
-	struct smp_alt_module *item;
-	unsigned long flags;
-
-	if (no_replacement || smp_alt_once)
-		return;
-
-	spin_lock_irqsave(&smp_alt, flags);
-	list_for_each_entry(item, &smp_alt_modules, next) {
-		if (mod != item->mod)
-			continue;
-		list_del(&item->next);
-		spin_unlock_irqrestore(&smp_alt, flags);
-		DPRINTK("%s: %s\n", __FUNCTION__, item->name);
-		kfree(item);
-		return;
-	}
-	spin_unlock_irqrestore(&smp_alt, flags);
-}
-
-void alternatives_smp_switch(int smp)
-{
-	struct smp_alt_module *mod;
-	unsigned long flags;
-
-#ifdef CONFIG_LOCKDEP
-	/*
-	 * A not yet fixed binutils section handling bug prevents
-	 * alternatives-replacement from working reliably, so turn
-	 * it off:
-	 */
-	printk("lockdep: not fixing up alternatives.\n");
-	return;
-#endif
-
-	if (no_replacement || smp_alt_once)
-		return;
-	BUG_ON(!smp && (num_online_cpus() > 1));
-
-	spin_lock_irqsave(&smp_alt, flags);
-	if (smp) {
-		printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
-		clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
-		clear_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
-		alternatives_smp_apply(__smp_alt_instructions,
-				       __smp_alt_instructions_end);
-		list_for_each_entry(mod, &smp_alt_modules, next)
-			alternatives_smp_lock(mod->locks, mod->locks_end,
-					      mod->text, mod->text_end);
-	} else {
-		printk(KERN_INFO "SMP alternatives: switching to UP code\n");
-		set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
-		set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
-		apply_alternatives(__smp_alt_instructions,
-				   __smp_alt_instructions_end);
-		list_for_each_entry(mod, &smp_alt_modules, next)
-			alternatives_smp_unlock(mod->locks, mod->locks_end,
-						mod->text, mod->text_end);
-	}
-	spin_unlock_irqrestore(&smp_alt, flags);
-}
-
-#endif
-
-void __init alternative_instructions(void)
-{
-	if (no_replacement) {
-		printk(KERN_INFO "(SMP-)alternatives turned off\n");
-		free_init_pages("SMP alternatives",
-				(unsigned long)__smp_alt_begin,
-				(unsigned long)__smp_alt_end);
-		return;
-	}
-	apply_alternatives(__alt_instructions, __alt_instructions_end);
-
-	/* switch to patch-once-at-boottime-only mode and free the
-	 * tables in case we know the number of CPUs will never ever
-	 * change */
-#ifdef CONFIG_HOTPLUG_CPU
-	if (num_possible_cpus() < 2)
-		smp_alt_once = 1;
-#else
-	smp_alt_once = 1;
-#endif
-
-#ifdef CONFIG_SMP
-	if (smp_alt_once) {
-		if (1 == num_possible_cpus()) {
-			printk(KERN_INFO "SMP alternatives: switching to UP code\n");
-			set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
-			set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
-			apply_alternatives(__smp_alt_instructions,
-					   __smp_alt_instructions_end);
-			alternatives_smp_unlock(__smp_locks, __smp_locks_end,
-						_text, _etext);
-		}
-		free_init_pages("SMP alternatives",
-				(unsigned long)__smp_alt_begin,
-				(unsigned long)__smp_alt_end);
-	} else {
-		alternatives_smp_save(__smp_alt_instructions,
-				      __smp_alt_instructions_end);
-		alternatives_smp_module_add(NULL, "core kernel",
-					    __smp_locks, __smp_locks_end,
-					    _text, _etext);
-		alternatives_smp_switch(0);
-	}
-#endif
-}
Index: head-2007-02-27/arch/x86_64/kernel/Makefile
===================================================================
--- head-2007-02-27.orig/arch/x86_64/kernel/Makefile	2007-02-27 16:27:18.000000000 +0100
+++ head-2007-02-27/arch/x86_64/kernel/Makefile	2007-02-27 16:27:27.000000000 +0100
@@ -62,7 +62,6 @@ time-y				+= ../../i386/kernel/time-xen.
 pci-dma-y			+= ../../i386/kernel/pci-dma-xen.o
 microcode-$(subst m,y,$(CONFIG_MICROCODE))  := ../../i386/kernel/microcode-xen.o
 quirks-y			:= ../../i386/kernel/quirks-xen.o
-alternative-y			:= ../../i386/kernel/alternative-xen.o
 
 n-obj-xen := i8259.o reboot.o i8237.o smpboot.o trampoline.o
 
Index: head-2007-02-27/arch/x86_64/mm/init-xen.c
===================================================================
--- head-2007-02-27.orig/arch/x86_64/mm/init-xen.c	2007-03-05 10:00:18.000000000 +0100
+++ head-2007-02-27/arch/x86_64/mm/init-xen.c	2007-03-05 10:13:48.000000000 +0100
@@ -404,6 +404,7 @@ static inline void __set_pte(pte_t *dst,
 
 static inline int make_readonly(unsigned long paddr)
 {
+	extern char __vsyscall_0;
 	int readonly = 0;
 
 	/* Make new page tables read-only. */
@@ -420,9 +421,12 @@ static inline int make_readonly(unsigned
 	/*
 	 * No need for writable mapping of kernel image. This also ensures that
 	 * page and descriptor tables embedded inside don't have writable
-	 * mappings. 
+	 * mappings. Exclude the vsyscall area here, allowing alternative
+	 * instruction patching to work.
 	 */
-	if ((paddr >= __pa_symbol(&_text)) && (paddr < __pa_symbol(&_end)))
+	if ((paddr >= __pa_symbol(&_text)) && (paddr < __pa_symbol(&_end))
+	    && !(paddr >= __pa_symbol(&__vsyscall_0)
+	         && paddr < __pa_symbol(&__vsyscall_0) + PAGE_SIZE))
 		readonly = 1;
 
 	return readonly;