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linux/arch/i386/kernel/alternative.c
Vivek Goyal 0dbf7028c0 [PATCH] x86: __pa and __pa_symbol address space separation 
Currently __pa_symbol is for use with symbols in the kernel address
map and __pa is for use with pointers into the physical memory map.
But the code is implemented so you can usually interchange the two.

__pa which is much more common can be implemented much more cheaply
if it is it doesn't have to worry about any other kernel address
spaces.  This is especially true with a relocatable kernel as
__pa_symbol needs to peform an extra variable read to resolve
the address.

There is a third macro that is added for the vsyscall data
__pa_vsymbol for finding the physical addesses of vsyscall pages.

Most of this patch is simply sorting through the references to
__pa or __pa_symbol and using the proper one.  A little of
it is continuing to use a physical address when we have it
instead of recalculating it several times.

swapper_pgd is now NULL.  leave_mm now uses init_mm.pgd
and init_mm.pgd is initialized at boot (instead of compile time)
to the physmem virtual mapping of init_level4_pgd.  The
physical address changed.

Except for the for EMPTY_ZERO page all of the remaining references
to __pa_symbol appear to be during kernel initialization.  So this
should reduce the cost of __pa in the common case, even on a relocated
kernel.

As this is technically a semantic change we need to be on the lookout
for anything I missed.  But it works for me (tm).

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
2007-05-02 19:27:07 +02:00

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#include <linux/module.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <asm/alternative.h>
#include <asm/sections.h>
static int smp_alt_once = 0;
static int debug_alternative = 0;
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("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 */
static void nop_out(void *insns, unsigned int len)
{
unsigned char **noptable = find_nop_table();
while (len > 0) {
unsigned int noplen = len;
if (noplen > ASM_NOP_MAX)
noplen = ASM_NOP_MAX;
memcpy(insns, noptable[noplen], noplen);
insns += noplen;
len -= noplen;
}
}
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)
{
struct alt_instr *a;
u8 *instr;
int diff;
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 = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__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;
nop_out(instr + a->replacementlen, diff);
}
}
#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)
{
u8 **ptr;
for (ptr = start; ptr < end; ptr++) {
if (*ptr < text)
continue;
if (*ptr > text_end)
continue;
nop_out(*ptr, 1);
};
}
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 (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 (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 (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
#ifdef CONFIG_PARAVIRT
void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end)
{
struct paravirt_patch *p;
for (p = start; p < end; p++) {
unsigned int used;
used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr,
p->len);
#ifdef CONFIG_DEBUG_PARAVIRT
{
int i;
/* Deliberately clobber regs using "not %reg" to find bugs. */
for (i = 0; i < 3; i++) {
if (p->len - used >= 2 && (p->clobbers & (1 << i))) {
memcpy(p->instr + used, "\xf7\xd0", 2);
p->instr[used+1] |= i;
used += 2;
}
}
}
#endif
/* Pad the rest with nops */
nop_out(p->instr + used, p->len - used);
}
/* Sync to be conservative, in case we patched following instructions */
sync_core();
}
extern struct paravirt_patch __start_parainstructions[],
__stop_parainstructions[];
#endif /* CONFIG_PARAVIRT */
void __init alternative_instructions(void)
{
unsigned long flags;
local_irq_save(flags);
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",
__pa_symbol(&__smp_alt_begin),
__pa_symbol(&__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
apply_paravirt(__start_parainstructions, __stop_parainstructions);
local_irq_restore(flags);
}
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