linux/arch/x86/kernel/paravirt.c
Juergen Gross 11af36cb89 x86/paravirt: Convert simple paravirt functions to asm
All functions referenced via __PV_IS_CALLEE_SAVE() need to be assembler
functions, as those functions calls are hidden from the compiler.

In case the kernel is compiled with "-fzero-call-used-regs" the compiler
will clobber caller-saved registers at the end of C functions, which
will result in unexpectedly zeroed registers at the call site of the
related paravirt functions.

Replace the C functions with DEFINE_PARAVIRT_ASM() constructs using
the same instructions as the related paravirt calls in the
PVOP_ALT_[V]CALLEE*() macros. And since they're not C functions visible
to the compiler anymore, latter won't do the callee-clobbered zeroing
invoked by -fzero-call-used-regs and thus won't corrupt registers.

  [ bp: Extend commit message. ]

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230317063325.361-1-jgross@suse.com
2023-03-17 13:29:47 +01:00

382 lines
9.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* Paravirtualization interfaces
Copyright (C) 2006 Rusty Russell IBM Corporation
2007 - x86_64 support added by Glauber de Oliveira Costa, Red Hat Inc
*/
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/efi.h>
#include <linux/bcd.h>
#include <linux/highmem.h>
#include <linux/kprobes.h>
#include <linux/pgtable.h>
#include <linux/static_call.h>
#include <asm/bug.h>
#include <asm/paravirt.h>
#include <asm/debugreg.h>
#include <asm/desc.h>
#include <asm/setup.h>
#include <asm/time.h>
#include <asm/pgalloc.h>
#include <asm/irq.h>
#include <asm/delay.h>
#include <asm/fixmap.h>
#include <asm/apic.h>
#include <asm/tlbflush.h>
#include <asm/timer.h>
#include <asm/special_insns.h>
#include <asm/tlb.h>
#include <asm/io_bitmap.h>
#include <asm/gsseg.h>
/*
* nop stub, which must not clobber anything *including the stack* to
* avoid confusing the entry prologues.
*/
DEFINE_PARAVIRT_ASM(_paravirt_nop, "", .entry.text);
/* stub always returning 0. */
DEFINE_PARAVIRT_ASM(paravirt_ret0, "xor %eax,%eax", .entry.text);
void __init default_banner(void)
{
printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
pv_info.name);
}
/* Undefined instruction for dealing with missing ops pointers. */
noinstr void paravirt_BUG(void)
{
BUG();
}
static unsigned paravirt_patch_call(void *insn_buff, const void *target,
unsigned long addr, unsigned len)
{
__text_gen_insn(insn_buff, CALL_INSN_OPCODE,
(void *)addr, target, CALL_INSN_SIZE);
return CALL_INSN_SIZE;
}
#ifdef CONFIG_PARAVIRT_XXL
DEFINE_PARAVIRT_ASM(_paravirt_ident_64, "mov %rdi, %rax", .text);
DEFINE_PARAVIRT_ASM(pv_native_save_fl, "pushf; pop %rax", .noinstr.text);
DEFINE_PARAVIRT_ASM(pv_native_irq_disable, "cli", .noinstr.text);
DEFINE_PARAVIRT_ASM(pv_native_irq_enable, "sti", .noinstr.text);
DEFINE_PARAVIRT_ASM(pv_native_read_cr2, "mov %cr2, %rax", .noinstr.text);
#endif
DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
void __init native_pv_lock_init(void)
{
if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
static_branch_disable(&virt_spin_lock_key);
}
unsigned int paravirt_patch(u8 type, void *insn_buff, unsigned long addr,
unsigned int len)
{
/*
* Neat trick to map patch type back to the call within the
* corresponding structure.
*/
void *opfunc = *((void **)&pv_ops + type);
unsigned ret;
if (opfunc == NULL)
/* If there's no function, patch it with paravirt_BUG() */
ret = paravirt_patch_call(insn_buff, paravirt_BUG, addr, len);
else if (opfunc == _paravirt_nop)
ret = 0;
else
/* Otherwise call the function. */
ret = paravirt_patch_call(insn_buff, opfunc, addr, len);
return ret;
}
struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;
static u64 native_steal_clock(int cpu)
{
return 0;
}
DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
DEFINE_STATIC_CALL(pv_sched_clock, native_sched_clock);
void paravirt_set_sched_clock(u64 (*func)(void))
{
static_call_update(pv_sched_clock, func);
}
/* These are in entry.S */
static struct resource reserve_ioports = {
.start = 0,
.end = IO_SPACE_LIMIT,
.name = "paravirt-ioport",
.flags = IORESOURCE_IO | IORESOURCE_BUSY,
};
/*
* Reserve the whole legacy IO space to prevent any legacy drivers
* from wasting time probing for their hardware. This is a fairly
* brute-force approach to disabling all non-virtual drivers.
*
* Note that this must be called very early to have any effect.
*/
int paravirt_disable_iospace(void)
{
return request_resource(&ioport_resource, &reserve_ioports);
}
static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
static inline void enter_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(this_cpu_read(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
this_cpu_write(paravirt_lazy_mode, mode);
}
static void leave_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(this_cpu_read(paravirt_lazy_mode) != mode);
this_cpu_write(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
}
void paravirt_enter_lazy_mmu(void)
{
enter_lazy(PARAVIRT_LAZY_MMU);
}
void paravirt_leave_lazy_mmu(void)
{
leave_lazy(PARAVIRT_LAZY_MMU);
}
void paravirt_flush_lazy_mmu(void)
{
preempt_disable();
if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
arch_leave_lazy_mmu_mode();
arch_enter_lazy_mmu_mode();
}
preempt_enable();
}
#ifdef CONFIG_PARAVIRT_XXL
void paravirt_start_context_switch(struct task_struct *prev)
{
BUG_ON(preemptible());
if (this_cpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
arch_leave_lazy_mmu_mode();
set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
}
enter_lazy(PARAVIRT_LAZY_CPU);
}
void paravirt_end_context_switch(struct task_struct *next)
{
BUG_ON(preemptible());
leave_lazy(PARAVIRT_LAZY_CPU);
if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
arch_enter_lazy_mmu_mode();
}
static noinstr void pv_native_write_cr2(unsigned long val)
{
native_write_cr2(val);
}
static noinstr unsigned long pv_native_get_debugreg(int regno)
{
return native_get_debugreg(regno);
}
static noinstr void pv_native_set_debugreg(int regno, unsigned long val)
{
native_set_debugreg(regno, val);
}
noinstr void pv_native_wbinvd(void)
{
native_wbinvd();
}
static noinstr void pv_native_safe_halt(void)
{
native_safe_halt();
}
#endif
enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
{
if (in_interrupt())
return PARAVIRT_LAZY_NONE;
return this_cpu_read(paravirt_lazy_mode);
}
struct pv_info pv_info = {
.name = "bare hardware",
#ifdef CONFIG_PARAVIRT_XXL
.extra_user_64bit_cs = __USER_CS,
#endif
};
/* 64-bit pagetable entries */
#define PTE_IDENT __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
struct paravirt_patch_template pv_ops = {
/* Cpu ops. */
.cpu.io_delay = native_io_delay,
#ifdef CONFIG_PARAVIRT_XXL
.cpu.cpuid = native_cpuid,
.cpu.get_debugreg = pv_native_get_debugreg,
.cpu.set_debugreg = pv_native_set_debugreg,
.cpu.read_cr0 = native_read_cr0,
.cpu.write_cr0 = native_write_cr0,
.cpu.write_cr4 = native_write_cr4,
.cpu.wbinvd = pv_native_wbinvd,
.cpu.read_msr = native_read_msr,
.cpu.write_msr = native_write_msr,
.cpu.read_msr_safe = native_read_msr_safe,
.cpu.write_msr_safe = native_write_msr_safe,
.cpu.read_pmc = native_read_pmc,
.cpu.load_tr_desc = native_load_tr_desc,
.cpu.set_ldt = native_set_ldt,
.cpu.load_gdt = native_load_gdt,
.cpu.load_idt = native_load_idt,
.cpu.store_tr = native_store_tr,
.cpu.load_tls = native_load_tls,
.cpu.load_gs_index = native_load_gs_index,
.cpu.write_ldt_entry = native_write_ldt_entry,
.cpu.write_gdt_entry = native_write_gdt_entry,
.cpu.write_idt_entry = native_write_idt_entry,
.cpu.alloc_ldt = paravirt_nop,
.cpu.free_ldt = paravirt_nop,
.cpu.load_sp0 = native_load_sp0,
#ifdef CONFIG_X86_IOPL_IOPERM
.cpu.invalidate_io_bitmap = native_tss_invalidate_io_bitmap,
.cpu.update_io_bitmap = native_tss_update_io_bitmap,
#endif
.cpu.start_context_switch = paravirt_nop,
.cpu.end_context_switch = paravirt_nop,
/* Irq ops. */
.irq.save_fl = __PV_IS_CALLEE_SAVE(pv_native_save_fl),
.irq.irq_disable = __PV_IS_CALLEE_SAVE(pv_native_irq_disable),
.irq.irq_enable = __PV_IS_CALLEE_SAVE(pv_native_irq_enable),
.irq.safe_halt = pv_native_safe_halt,
.irq.halt = native_halt,
#endif /* CONFIG_PARAVIRT_XXL */
/* Mmu ops. */
.mmu.flush_tlb_user = native_flush_tlb_local,
.mmu.flush_tlb_kernel = native_flush_tlb_global,
.mmu.flush_tlb_one_user = native_flush_tlb_one_user,
.mmu.flush_tlb_multi = native_flush_tlb_multi,
.mmu.tlb_remove_table =
(void (*)(struct mmu_gather *, void *))tlb_remove_page,
.mmu.exit_mmap = paravirt_nop,
.mmu.notify_page_enc_status_changed = paravirt_nop,
#ifdef CONFIG_PARAVIRT_XXL
.mmu.read_cr2 = __PV_IS_CALLEE_SAVE(pv_native_read_cr2),
.mmu.write_cr2 = pv_native_write_cr2,
.mmu.read_cr3 = __native_read_cr3,
.mmu.write_cr3 = native_write_cr3,
.mmu.pgd_alloc = __paravirt_pgd_alloc,
.mmu.pgd_free = paravirt_nop,
.mmu.alloc_pte = paravirt_nop,
.mmu.alloc_pmd = paravirt_nop,
.mmu.alloc_pud = paravirt_nop,
.mmu.alloc_p4d = paravirt_nop,
.mmu.release_pte = paravirt_nop,
.mmu.release_pmd = paravirt_nop,
.mmu.release_pud = paravirt_nop,
.mmu.release_p4d = paravirt_nop,
.mmu.set_pte = native_set_pte,
.mmu.set_pmd = native_set_pmd,
.mmu.ptep_modify_prot_start = __ptep_modify_prot_start,
.mmu.ptep_modify_prot_commit = __ptep_modify_prot_commit,
.mmu.set_pud = native_set_pud,
.mmu.pmd_val = PTE_IDENT,
.mmu.make_pmd = PTE_IDENT,
.mmu.pud_val = PTE_IDENT,
.mmu.make_pud = PTE_IDENT,
.mmu.set_p4d = native_set_p4d,
#if CONFIG_PGTABLE_LEVELS >= 5
.mmu.p4d_val = PTE_IDENT,
.mmu.make_p4d = PTE_IDENT,
.mmu.set_pgd = native_set_pgd,
#endif /* CONFIG_PGTABLE_LEVELS >= 5 */
.mmu.pte_val = PTE_IDENT,
.mmu.pgd_val = PTE_IDENT,
.mmu.make_pte = PTE_IDENT,
.mmu.make_pgd = PTE_IDENT,
.mmu.enter_mmap = paravirt_nop,
.mmu.lazy_mode = {
.enter = paravirt_nop,
.leave = paravirt_nop,
.flush = paravirt_nop,
},
.mmu.set_fixmap = native_set_fixmap,
#endif /* CONFIG_PARAVIRT_XXL */
#if defined(CONFIG_PARAVIRT_SPINLOCKS)
/* Lock ops. */
#ifdef CONFIG_SMP
.lock.queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
.lock.queued_spin_unlock =
PV_CALLEE_SAVE(__native_queued_spin_unlock),
.lock.wait = paravirt_nop,
.lock.kick = paravirt_nop,
.lock.vcpu_is_preempted =
PV_CALLEE_SAVE(__native_vcpu_is_preempted),
#endif /* SMP */
#endif
};
#ifdef CONFIG_PARAVIRT_XXL
NOKPROBE_SYMBOL(native_load_idt);
#endif
EXPORT_SYMBOL(pv_ops);
EXPORT_SYMBOL_GPL(pv_info);