Jan Beulich
2007-Mar-05 10:20 UTC
[Xen-devel] [PATCH 2/3] linux 2.6.18 merge: eliminate Xen specials: alternative.c
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;
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