diff --git a/arch/x86/hyperv/hv_crash.c b/arch/x86/hyperv/hv_crash.c index 92da1b4f2e73..fdb277bf73d8 100644 --- a/arch/x86/hyperv/hv_crash.c +++ b/arch/x86/hyperv/hv_crash.c @@ -107,14 +107,12 @@ static void __noreturn hv_panic_timeout_reboot(void) cpu_relax(); } -/* This cannot be inlined as it needs stack */ -static noinline __noclone void hv_crash_restore_tss(void) +static void hv_crash_restore_tss(void) { load_TR_desc(); } -/* This cannot be inlined as it needs stack */ -static noinline void hv_crash_clear_kernpt(void) +static void hv_crash_clear_kernpt(void) { pgd_t *pgd; p4d_t *p4d; @@ -125,50 +123,9 @@ static noinline void hv_crash_clear_kernpt(void) native_p4d_clear(p4d); } -/* - * This is the C entry point from the asm glue code after the disable hypercall. - * We enter here in IA32-e long mode, ie, full 64bit mode running on kernel - * page tables with our below 4G page identity mapped, but using a temporary - * GDT. ds/fs/gs/es are null. ss is not usable. bp is null. stack is not - * available. We restore kernel GDT, and rest of the context, and continue - * to kexec. - */ -static asmlinkage void __noreturn hv_crash_c_entry(void) + +static void __noreturn hv_crash_handle(void) { - struct hv_crash_ctxt *ctxt = &hv_crash_ctxt; - - /* first thing, restore kernel gdt */ - native_load_gdt(&ctxt->gdtr); - - asm volatile("movw %%ax, %%ss" : : "a"(ctxt->ss)); - asm volatile("movq %0, %%rsp" : : "m"(ctxt->rsp)); - - asm volatile("movw %%ax, %%ds" : : "a"(ctxt->ds)); - asm volatile("movw %%ax, %%es" : : "a"(ctxt->es)); - asm volatile("movw %%ax, %%fs" : : "a"(ctxt->fs)); - asm volatile("movw %%ax, %%gs" : : "a"(ctxt->gs)); - - native_wrmsrq(MSR_IA32_CR_PAT, ctxt->pat); - asm volatile("movq %0, %%cr0" : : "r"(ctxt->cr0)); - - asm volatile("movq %0, %%cr8" : : "r"(ctxt->cr8)); - asm volatile("movq %0, %%cr4" : : "r"(ctxt->cr4)); - asm volatile("movq %0, %%cr2" : : "r"(ctxt->cr4)); - - native_load_idt(&ctxt->idtr); - native_wrmsrq(MSR_GS_BASE, ctxt->gsbase); - native_wrmsrq(MSR_EFER, ctxt->efer); - - /* restore the original kernel CS now via far return */ - asm volatile("movzwq %0, %%rax\n\t" - "pushq %%rax\n\t" - "pushq $1f\n\t" - "lretq\n\t" - "1:nop\n\t" : : "m"(ctxt->cs) : "rax"); - - /* We are in asmlinkage without stack frame, hence make C function - * calls which will buy stack frames. - */ hv_crash_restore_tss(); hv_crash_clear_kernpt(); @@ -177,7 +134,54 @@ static asmlinkage void __noreturn hv_crash_c_entry(void) hv_panic_timeout_reboot(); } -/* Tell gcc we are using lretq long jump in the above function intentionally */ + +/* + * __naked functions do not permit function calls, not even to __always_inline + * functions that only contain asm() blocks themselves. So use a macro instead. + */ +#define hv_wrmsr(msr, val) \ + asm volatile("wrmsr" :: "c"(msr), "a"((u32)val), "d"((u32)(val >> 32)) : "memory") + +/* + * This is the C entry point from the asm glue code after the disable hypercall. + * We enter here in IA32-e long mode, ie, full 64bit mode running on kernel + * page tables with our below 4G page identity mapped, but using a temporary + * GDT. ds/fs/gs/es are null. ss is not usable. bp is null. stack is not + * available. We restore kernel GDT, and rest of the context, and continue + * to kexec. + */ +static void __naked hv_crash_c_entry(void) +{ + /* first thing, restore kernel gdt */ + asm volatile("lgdt %0" : : "m" (hv_crash_ctxt.gdtr)); + + asm volatile("movw %0, %%ss\n\t" + "movq %1, %%rsp" + :: "m"(hv_crash_ctxt.ss), "m"(hv_crash_ctxt.rsp)); + + asm volatile("movw %0, %%ds" : : "m"(hv_crash_ctxt.ds)); + asm volatile("movw %0, %%es" : : "m"(hv_crash_ctxt.es)); + asm volatile("movw %0, %%fs" : : "m"(hv_crash_ctxt.fs)); + asm volatile("movw %0, %%gs" : : "m"(hv_crash_ctxt.gs)); + + hv_wrmsr(MSR_IA32_CR_PAT, hv_crash_ctxt.pat); + asm volatile("movq %0, %%cr0" : : "r"(hv_crash_ctxt.cr0)); + + asm volatile("movq %0, %%cr8" : : "r"(hv_crash_ctxt.cr8)); + asm volatile("movq %0, %%cr4" : : "r"(hv_crash_ctxt.cr4)); + asm volatile("movq %0, %%cr2" : : "r"(hv_crash_ctxt.cr2)); + + asm volatile("lidt %0" : : "m" (hv_crash_ctxt.idtr)); + hv_wrmsr(MSR_GS_BASE, hv_crash_ctxt.gsbase); + hv_wrmsr(MSR_EFER, hv_crash_ctxt.efer); + + /* restore the original kernel CS now via far return */ + asm volatile("pushq %q0\n\t" + "pushq %q1\n\t" + "lretq" + :: "r"(hv_crash_ctxt.cs), "r"(hv_crash_handle)); +} +/* Tell objtool we are using lretq long jump in the above function intentionally */ STACK_FRAME_NON_STANDARD(hv_crash_c_entry); static void hv_mark_tss_not_busy(void)