[PATCH] paravirt: Patch inline replacements for paravirt intercepts

[mirror_ubuntu-artful-kernel.git] / arch / i386 / kernel / paravirt.c

diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 478192cd4b90db06fb48d908252f7dc601f643b3..d46460426446bc1756d102b05b76e2a7f0b52d5f 100644 (file)
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -45,6 +45,49 @@ char *memory_setup(void)
        return paravirt_ops.memory_setup();
 }
 
+/* Simple instruction patching code. */
+#define DEF_NATIVE(name, code)                                 \
+       extern const char start_##name[], end_##name[];         \
+       asm("start_" #name ": " code "; end_" #name ":")
+DEF_NATIVE(cli, "cli");
+DEF_NATIVE(sti, "sti");
+DEF_NATIVE(popf, "push %eax; popf");
+DEF_NATIVE(pushf, "pushf; pop %eax");
+DEF_NATIVE(pushf_cli, "pushf; pop %eax; cli");
+DEF_NATIVE(iret, "iret");
+DEF_NATIVE(sti_sysexit, "sti; sysexit");
+
+static const struct native_insns
+{
+       const char *start, *end;
+} native_insns[] = {
+       [PARAVIRT_IRQ_DISABLE] = { start_cli, end_cli },
+       [PARAVIRT_IRQ_ENABLE] = { start_sti, end_sti },
+       [PARAVIRT_RESTORE_FLAGS] = { start_popf, end_popf },
+       [PARAVIRT_SAVE_FLAGS] = { start_pushf, end_pushf },
+       [PARAVIRT_SAVE_FLAGS_IRQ_DISABLE] = { start_pushf_cli, end_pushf_cli },
+       [PARAVIRT_INTERRUPT_RETURN] = { start_iret, end_iret },
+       [PARAVIRT_STI_SYSEXIT] = { start_sti_sysexit, end_sti_sysexit },
+};
+
+static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+{
+       unsigned int insn_len;
+
+       /* Don't touch it if we don't have a replacement */
+       if (type >= ARRAY_SIZE(native_insns) || !native_insns[type].start)
+               return len;
+
+       insn_len = native_insns[type].end - native_insns[type].start;
+
+       /* Similarly if we can't fit replacement. */
+       if (len < insn_len)
+               return len;
+
+       memcpy(insns, native_insns[type].start, insn_len);
+       return insn_len;
+}
+
 static fastcall unsigned long native_get_debugreg(int regno)
 {
        unsigned long val = 0;  /* Damn you, gcc! */
@@ -349,6 +392,7 @@ struct paravirt_ops paravirt_ops = {
        .paravirt_enabled = 0,
        .kernel_rpl = 0,
 
+       .patch = native_patch,
        .banner = default_banner,
        .arch_setup = native_nop,
        .memory_setup = machine_specific_memory_setup,