63f70270cc
Implement the actual patching machinery. paravirt_patch_default()
contains the logic to automatically patch a callsite based on a few
simple rules:
- if the paravirt_op function is paravirt_nop, then patch nops
- if the paravirt_op function is a jmp target, then jmp to it
- if the paravirt_op function is callable and doesn't clobber too much
for the callsite, call it directly
paravirt_patch_default is suitable as a default implementation of
paravirt_ops.patch, will remove most of the expensive indirect calls
in favour of either a direct call or a pile of nops.
Backends may implement their own patcher, however. There are several
helper functions to help with this:
paravirt_patch_nop nop out a callsite
paravirt_patch_ignore leave the callsite as-is
paravirt_patch_call patch a call if the caller and callee
have compatible clobbers
paravirt_patch_jmp patch in a jmp
paravirt_patch_insns patch some literal instructions over
the callsite, if they fit
This patch also implements more direct patches for the native case, so
that when running on native hardware many common operations are
implemented inline.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>
Acked-by: Ingo Molnar <mingo@elte.hu>
392 lines
9.2 KiB
C
392 lines
9.2 KiB
C
#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/list.h>
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#include <asm/alternative.h>
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#include <asm/sections.h>
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static int noreplace_smp = 0;
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static int smp_alt_once = 0;
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static int debug_alternative = 0;
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static int __init bootonly(char *str)
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{
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smp_alt_once = 1;
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return 1;
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}
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__setup("smp-alt-boot", bootonly);
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static int __init debug_alt(char *str)
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{
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debug_alternative = 1;
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return 1;
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}
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__setup("debug-alternative", debug_alt);
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static int __init setup_noreplace_smp(char *str)
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{
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noreplace_smp = 1;
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return 1;
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}
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__setup("noreplace-smp", setup_noreplace_smp);
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#define DPRINTK(fmt, args...) if (debug_alternative) \
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printk(KERN_DEBUG fmt, args)
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#ifdef GENERIC_NOP1
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/* Use inline assembly to define this because the nops are defined
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as inline assembly strings in the include files and we cannot
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get them easily into strings. */
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asm("\t.data\nintelnops: "
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GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
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GENERIC_NOP7 GENERIC_NOP8);
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extern unsigned char intelnops[];
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static unsigned char *intel_nops[ASM_NOP_MAX+1] = {
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NULL,
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intelnops,
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intelnops + 1,
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intelnops + 1 + 2,
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intelnops + 1 + 2 + 3,
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intelnops + 1 + 2 + 3 + 4,
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intelnops + 1 + 2 + 3 + 4 + 5,
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intelnops + 1 + 2 + 3 + 4 + 5 + 6,
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intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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};
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#endif
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#ifdef K8_NOP1
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asm("\t.data\nk8nops: "
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K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
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K8_NOP7 K8_NOP8);
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extern unsigned char k8nops[];
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static unsigned char *k8_nops[ASM_NOP_MAX+1] = {
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NULL,
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k8nops,
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k8nops + 1,
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k8nops + 1 + 2,
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k8nops + 1 + 2 + 3,
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k8nops + 1 + 2 + 3 + 4,
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k8nops + 1 + 2 + 3 + 4 + 5,
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k8nops + 1 + 2 + 3 + 4 + 5 + 6,
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k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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};
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#endif
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#ifdef K7_NOP1
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asm("\t.data\nk7nops: "
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K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
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K7_NOP7 K7_NOP8);
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extern unsigned char k7nops[];
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static unsigned char *k7_nops[ASM_NOP_MAX+1] = {
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NULL,
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k7nops,
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k7nops + 1,
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k7nops + 1 + 2,
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k7nops + 1 + 2 + 3,
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k7nops + 1 + 2 + 3 + 4,
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k7nops + 1 + 2 + 3 + 4 + 5,
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k7nops + 1 + 2 + 3 + 4 + 5 + 6,
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k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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};
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#endif
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#ifdef CONFIG_X86_64
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extern char __vsyscall_0;
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static inline unsigned char** find_nop_table(void)
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{
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return k8_nops;
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}
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#else /* CONFIG_X86_64 */
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static struct nop {
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int cpuid;
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unsigned char **noptable;
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} noptypes[] = {
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{ X86_FEATURE_K8, k8_nops },
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{ X86_FEATURE_K7, k7_nops },
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{ -1, NULL }
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};
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static unsigned char** find_nop_table(void)
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{
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unsigned char **noptable = intel_nops;
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int i;
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for (i = 0; noptypes[i].cpuid >= 0; i++) {
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if (boot_cpu_has(noptypes[i].cpuid)) {
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noptable = noptypes[i].noptable;
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break;
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}
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}
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return noptable;
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}
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#endif /* CONFIG_X86_64 */
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static void nop_out(void *insns, unsigned int len)
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{
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unsigned char **noptable = find_nop_table();
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while (len > 0) {
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unsigned int noplen = len;
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if (noplen > ASM_NOP_MAX)
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noplen = ASM_NOP_MAX;
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memcpy(insns, noptable[noplen], noplen);
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insns += noplen;
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len -= noplen;
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}
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}
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extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
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extern u8 *__smp_locks[], *__smp_locks_end[];
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/* Replace instructions with better alternatives for this CPU type.
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This runs before SMP is initialized to avoid SMP problems with
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self modifying code. This implies that assymetric systems where
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APs have less capabilities than the boot processor are not handled.
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Tough. Make sure you disable such features by hand. */
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void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
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{
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struct alt_instr *a;
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u8 *instr;
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int diff;
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DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
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for (a = start; a < end; a++) {
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BUG_ON(a->replacementlen > a->instrlen);
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if (!boot_cpu_has(a->cpuid))
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continue;
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instr = a->instr;
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#ifdef CONFIG_X86_64
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/* vsyscall code is not mapped yet. resolve it manually. */
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if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
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instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
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DPRINTK("%s: vsyscall fixup: %p => %p\n",
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__FUNCTION__, a->instr, instr);
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}
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#endif
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memcpy(instr, a->replacement, a->replacementlen);
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diff = a->instrlen - a->replacementlen;
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nop_out(instr + a->replacementlen, diff);
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}
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}
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#ifdef CONFIG_SMP
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static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
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{
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u8 **ptr;
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for (ptr = start; ptr < end; ptr++) {
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if (*ptr < text)
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continue;
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if (*ptr > text_end)
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continue;
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**ptr = 0xf0; /* lock prefix */
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};
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}
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static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
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{
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u8 **ptr;
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if (noreplace_smp)
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return;
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for (ptr = start; ptr < end; ptr++) {
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if (*ptr < text)
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continue;
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if (*ptr > text_end)
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continue;
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nop_out(*ptr, 1);
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};
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}
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struct smp_alt_module {
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/* what is this ??? */
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struct module *mod;
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char *name;
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/* ptrs to lock prefixes */
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u8 **locks;
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u8 **locks_end;
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/* .text segment, needed to avoid patching init code ;) */
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u8 *text;
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u8 *text_end;
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struct list_head next;
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};
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static LIST_HEAD(smp_alt_modules);
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static DEFINE_SPINLOCK(smp_alt);
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void alternatives_smp_module_add(struct module *mod, char *name,
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void *locks, void *locks_end,
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void *text, void *text_end)
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{
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struct smp_alt_module *smp;
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unsigned long flags;
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if (noreplace_smp)
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return;
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if (smp_alt_once) {
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if (boot_cpu_has(X86_FEATURE_UP))
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alternatives_smp_unlock(locks, locks_end,
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text, text_end);
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return;
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}
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smp = kzalloc(sizeof(*smp), GFP_KERNEL);
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if (NULL == smp)
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return; /* we'll run the (safe but slow) SMP code then ... */
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smp->mod = mod;
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smp->name = name;
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smp->locks = locks;
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smp->locks_end = locks_end;
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smp->text = text;
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smp->text_end = text_end;
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DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n",
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__FUNCTION__, smp->locks, smp->locks_end,
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smp->text, smp->text_end, smp->name);
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spin_lock_irqsave(&smp_alt, flags);
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list_add_tail(&smp->next, &smp_alt_modules);
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if (boot_cpu_has(X86_FEATURE_UP))
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alternatives_smp_unlock(smp->locks, smp->locks_end,
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smp->text, smp->text_end);
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spin_unlock_irqrestore(&smp_alt, flags);
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}
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void alternatives_smp_module_del(struct module *mod)
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{
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struct smp_alt_module *item;
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unsigned long flags;
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if (smp_alt_once || noreplace_smp)
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return;
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spin_lock_irqsave(&smp_alt, flags);
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list_for_each_entry(item, &smp_alt_modules, next) {
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if (mod != item->mod)
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continue;
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list_del(&item->next);
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spin_unlock_irqrestore(&smp_alt, flags);
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DPRINTK("%s: %s\n", __FUNCTION__, item->name);
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kfree(item);
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return;
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}
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spin_unlock_irqrestore(&smp_alt, flags);
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}
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void alternatives_smp_switch(int smp)
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{
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struct smp_alt_module *mod;
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unsigned long flags;
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#ifdef CONFIG_LOCKDEP
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/*
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* A not yet fixed binutils section handling bug prevents
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* alternatives-replacement from working reliably, so turn
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* it off:
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*/
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printk("lockdep: not fixing up alternatives.\n");
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return;
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#endif
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if (noreplace_smp || smp_alt_once)
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return;
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BUG_ON(!smp && (num_online_cpus() > 1));
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spin_lock_irqsave(&smp_alt, flags);
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if (smp) {
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printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
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clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
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clear_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
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list_for_each_entry(mod, &smp_alt_modules, next)
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alternatives_smp_lock(mod->locks, mod->locks_end,
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mod->text, mod->text_end);
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} else {
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printk(KERN_INFO "SMP alternatives: switching to UP code\n");
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set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
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set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
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list_for_each_entry(mod, &smp_alt_modules, next)
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alternatives_smp_unlock(mod->locks, mod->locks_end,
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mod->text, mod->text_end);
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}
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spin_unlock_irqrestore(&smp_alt, flags);
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}
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#endif
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#ifdef CONFIG_PARAVIRT
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void apply_paravirt(struct paravirt_patch_site *start,
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struct paravirt_patch_site *end)
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{
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struct paravirt_patch_site *p;
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for (p = start; p < end; p++) {
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unsigned int used;
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used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr,
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p->len);
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BUG_ON(used > p->len);
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/* Pad the rest with nops */
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nop_out(p->instr + used, p->len - used);
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}
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/* Sync to be conservative, in case we patched following
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* instructions */
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sync_core();
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}
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extern struct paravirt_patch_site __start_parainstructions[],
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__stop_parainstructions[];
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#endif /* CONFIG_PARAVIRT */
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void __init alternative_instructions(void)
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{
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unsigned long flags;
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local_irq_save(flags);
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apply_alternatives(__alt_instructions, __alt_instructions_end);
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/* switch to patch-once-at-boottime-only mode and free the
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* tables in case we know the number of CPUs will never ever
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* change */
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#ifdef CONFIG_HOTPLUG_CPU
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if (num_possible_cpus() < 2)
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smp_alt_once = 1;
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#else
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smp_alt_once = 1;
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#endif
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#ifdef CONFIG_SMP
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if (smp_alt_once) {
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if (1 == num_possible_cpus()) {
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printk(KERN_INFO "SMP alternatives: switching to UP code\n");
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set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
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set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
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alternatives_smp_unlock(__smp_locks, __smp_locks_end,
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_text, _etext);
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}
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free_init_pages("SMP alternatives",
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__pa_symbol(&__smp_locks),
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__pa_symbol(&__smp_locks_end));
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} else {
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alternatives_smp_module_add(NULL, "core kernel",
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__smp_locks, __smp_locks_end,
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_text, _etext);
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alternatives_smp_switch(0);
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}
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#endif
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apply_paravirt(__start_parainstructions, __stop_parainstructions);
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local_irq_restore(flags);
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}
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