![Andy Lutomirski](/assets/img/avatar_default.png)
PARAVIRT_ADJUST_EXCEPTION_FRAME generates this code (using nmi as an example, trimmed for readability): ff 15 00 00 00 00 callq *0x0(%rip) # 2796 <nmi+0x6> 2792: R_X86_64_PC32 pv_irq_ops+0x2c That's a call through a function pointer to regular C function that does nothing on native boots, but that function isn't protected against kprobes, isn't marked notrace, and is certainly not guaranteed to preserve any registers if the compiler is feeling perverse. This is bad news for a CLBR_NONE operation. Of course, if everything works correctly, once paravirt ops are patched, it gets nopped out, but what if we hit this code before paravirt ops are patched in? This can potentially cause breakage that is very difficult to debug. A more subtle failure is possible here, too: if _paravirt_nop uses the stack at all (even just to push RBP), it will overwrite the "NMI executing" variable if it's called in the NMI prologue. The Xen case, perhaps surprisingly, is fine, because it's already written in asm. Fix all of the cases that default to paravirt_nop (including adjust_exception_frame) with a big hammer: replace paravirt_nop with an asm function that is just a ret instruction. The Xen case may have other problems, so document them. This is part of a fix for some random crashes that Sasha saw. Reported-and-tested-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/8f5d2ba295f9d73751c33d97fda03e0495d9ade0.1442791737.git.luto@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
498 lines
12 KiB
C
498 lines
12 KiB
C
/* Paravirtualization interfaces
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Copyright (C) 2006 Rusty Russell IBM Corporation
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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2007 - x86_64 support added by Glauber de Oliveira Costa, Red Hat Inc
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*/
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#include <linux/errno.h>
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#include <linux/module.h>
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#include <linux/efi.h>
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#include <linux/bcd.h>
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#include <linux/highmem.h>
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#include <linux/kprobes.h>
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#include <asm/bug.h>
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#include <asm/paravirt.h>
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#include <asm/debugreg.h>
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#include <asm/desc.h>
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#include <asm/setup.h>
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#include <asm/pgtable.h>
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#include <asm/time.h>
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#include <asm/pgalloc.h>
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#include <asm/irq.h>
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#include <asm/delay.h>
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#include <asm/fixmap.h>
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#include <asm/apic.h>
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#include <asm/tlbflush.h>
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#include <asm/timer.h>
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#include <asm/special_insns.h>
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/*
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* nop stub, which must not clobber anything *including the stack* to
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* avoid confusing the entry prologues.
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*/
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extern void _paravirt_nop(void);
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asm (".pushsection .entry.text, \"ax\"\n"
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".global _paravirt_nop\n"
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"_paravirt_nop:\n\t"
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"ret\n\t"
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".size _paravirt_nop, . - _paravirt_nop\n\t"
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".type _paravirt_nop, @function\n\t"
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".popsection");
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/* identity function, which can be inlined */
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u32 _paravirt_ident_32(u32 x)
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{
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return x;
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}
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u64 _paravirt_ident_64(u64 x)
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{
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return x;
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}
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void __init default_banner(void)
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{
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printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
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pv_info.name);
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}
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/* Undefined instruction for dealing with missing ops pointers. */
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static const unsigned char ud2a[] = { 0x0f, 0x0b };
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unsigned paravirt_patch_nop(void)
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{
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return 0;
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}
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unsigned paravirt_patch_ignore(unsigned len)
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{
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return len;
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}
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struct branch {
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unsigned char opcode;
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u32 delta;
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} __attribute__((packed));
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unsigned paravirt_patch_call(void *insnbuf,
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const void *target, u16 tgt_clobbers,
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unsigned long addr, u16 site_clobbers,
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unsigned len)
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{
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struct branch *b = insnbuf;
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unsigned long delta = (unsigned long)target - (addr+5);
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if (tgt_clobbers & ~site_clobbers)
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return len; /* target would clobber too much for this site */
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if (len < 5)
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return len; /* call too long for patch site */
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b->opcode = 0xe8; /* call */
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b->delta = delta;
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BUILD_BUG_ON(sizeof(*b) != 5);
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return 5;
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}
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unsigned paravirt_patch_jmp(void *insnbuf, const void *target,
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unsigned long addr, unsigned len)
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{
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struct branch *b = insnbuf;
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unsigned long delta = (unsigned long)target - (addr+5);
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if (len < 5)
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return len; /* call too long for patch site */
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b->opcode = 0xe9; /* jmp */
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b->delta = delta;
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return 5;
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}
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/* Neat trick to map patch type back to the call within the
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* corresponding structure. */
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static void *get_call_destination(u8 type)
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{
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struct paravirt_patch_template tmpl = {
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.pv_init_ops = pv_init_ops,
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.pv_time_ops = pv_time_ops,
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.pv_cpu_ops = pv_cpu_ops,
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.pv_irq_ops = pv_irq_ops,
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.pv_apic_ops = pv_apic_ops,
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.pv_mmu_ops = pv_mmu_ops,
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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.pv_lock_ops = pv_lock_ops,
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#endif
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};
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return *((void **)&tmpl + type);
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}
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unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
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unsigned long addr, unsigned len)
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{
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void *opfunc = get_call_destination(type);
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unsigned ret;
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if (opfunc == NULL)
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/* If there's no function, patch it with a ud2a (BUG) */
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ret = paravirt_patch_insns(insnbuf, len, ud2a, ud2a+sizeof(ud2a));
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else if (opfunc == _paravirt_nop)
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/* If the operation is a nop, then nop the callsite */
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ret = paravirt_patch_nop();
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/* identity functions just return their single argument */
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else if (opfunc == _paravirt_ident_32)
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ret = paravirt_patch_ident_32(insnbuf, len);
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else if (opfunc == _paravirt_ident_64)
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ret = paravirt_patch_ident_64(insnbuf, len);
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else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) ||
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#ifdef CONFIG_X86_32
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type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) ||
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#endif
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type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) ||
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type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64))
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/* If operation requires a jmp, then jmp */
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ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len);
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else
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/* Otherwise call the function; assume target could
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clobber any caller-save reg */
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ret = paravirt_patch_call(insnbuf, opfunc, CLBR_ANY,
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addr, clobbers, len);
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return ret;
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}
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unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
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const char *start, const char *end)
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{
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unsigned insn_len = end - start;
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if (insn_len > len || start == NULL)
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insn_len = len;
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else
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memcpy(insnbuf, start, insn_len);
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return insn_len;
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}
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static void native_flush_tlb(void)
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{
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__native_flush_tlb();
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}
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/*
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* Global pages have to be flushed a bit differently. Not a real
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* performance problem because this does not happen often.
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*/
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static void native_flush_tlb_global(void)
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{
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__native_flush_tlb_global();
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}
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static void native_flush_tlb_single(unsigned long addr)
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{
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__native_flush_tlb_single(addr);
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}
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struct static_key paravirt_steal_enabled;
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struct static_key paravirt_steal_rq_enabled;
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static u64 native_steal_clock(int cpu)
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{
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return 0;
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}
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/* These are in entry.S */
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extern void native_iret(void);
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extern void native_irq_enable_sysexit(void);
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extern void native_usergs_sysret32(void);
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extern void native_usergs_sysret64(void);
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static struct resource reserve_ioports = {
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.start = 0,
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.end = IO_SPACE_LIMIT,
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.name = "paravirt-ioport",
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.flags = IORESOURCE_IO | IORESOURCE_BUSY,
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};
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/*
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* Reserve the whole legacy IO space to prevent any legacy drivers
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* from wasting time probing for their hardware. This is a fairly
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* brute-force approach to disabling all non-virtual drivers.
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*
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* Note that this must be called very early to have any effect.
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*/
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int paravirt_disable_iospace(void)
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{
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return request_resource(&ioport_resource, &reserve_ioports);
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}
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static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
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static inline void enter_lazy(enum paravirt_lazy_mode mode)
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{
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BUG_ON(this_cpu_read(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
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this_cpu_write(paravirt_lazy_mode, mode);
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}
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static void leave_lazy(enum paravirt_lazy_mode mode)
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{
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BUG_ON(this_cpu_read(paravirt_lazy_mode) != mode);
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this_cpu_write(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
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}
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void paravirt_enter_lazy_mmu(void)
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{
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enter_lazy(PARAVIRT_LAZY_MMU);
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}
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void paravirt_leave_lazy_mmu(void)
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{
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leave_lazy(PARAVIRT_LAZY_MMU);
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}
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void paravirt_flush_lazy_mmu(void)
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{
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preempt_disable();
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if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
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arch_leave_lazy_mmu_mode();
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arch_enter_lazy_mmu_mode();
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}
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preempt_enable();
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}
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void paravirt_start_context_switch(struct task_struct *prev)
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{
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BUG_ON(preemptible());
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if (this_cpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
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arch_leave_lazy_mmu_mode();
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set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
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}
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enter_lazy(PARAVIRT_LAZY_CPU);
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}
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void paravirt_end_context_switch(struct task_struct *next)
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{
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BUG_ON(preemptible());
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leave_lazy(PARAVIRT_LAZY_CPU);
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if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
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arch_enter_lazy_mmu_mode();
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}
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enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
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{
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if (in_interrupt())
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return PARAVIRT_LAZY_NONE;
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return this_cpu_read(paravirt_lazy_mode);
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}
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struct pv_info pv_info = {
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.name = "bare hardware",
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.paravirt_enabled = 0,
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.kernel_rpl = 0,
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.shared_kernel_pmd = 1, /* Only used when CONFIG_X86_PAE is set */
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#ifdef CONFIG_X86_64
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.extra_user_64bit_cs = __USER_CS,
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#endif
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};
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struct pv_init_ops pv_init_ops = {
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.patch = native_patch,
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};
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struct pv_time_ops pv_time_ops = {
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.sched_clock = native_sched_clock,
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.steal_clock = native_steal_clock,
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};
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__visible struct pv_irq_ops pv_irq_ops = {
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.save_fl = __PV_IS_CALLEE_SAVE(native_save_fl),
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.restore_fl = __PV_IS_CALLEE_SAVE(native_restore_fl),
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.irq_disable = __PV_IS_CALLEE_SAVE(native_irq_disable),
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.irq_enable = __PV_IS_CALLEE_SAVE(native_irq_enable),
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.safe_halt = native_safe_halt,
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.halt = native_halt,
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#ifdef CONFIG_X86_64
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.adjust_exception_frame = paravirt_nop,
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#endif
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};
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__visible struct pv_cpu_ops pv_cpu_ops = {
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.cpuid = native_cpuid,
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.get_debugreg = native_get_debugreg,
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.set_debugreg = native_set_debugreg,
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.clts = native_clts,
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.read_cr0 = native_read_cr0,
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.write_cr0 = native_write_cr0,
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.read_cr4 = native_read_cr4,
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.read_cr4_safe = native_read_cr4_safe,
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.write_cr4 = native_write_cr4,
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#ifdef CONFIG_X86_64
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.read_cr8 = native_read_cr8,
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.write_cr8 = native_write_cr8,
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#endif
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.wbinvd = native_wbinvd,
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.read_msr = native_read_msr_safe,
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.write_msr = native_write_msr_safe,
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.read_pmc = native_read_pmc,
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.load_tr_desc = native_load_tr_desc,
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.set_ldt = native_set_ldt,
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.load_gdt = native_load_gdt,
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.load_idt = native_load_idt,
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.store_idt = native_store_idt,
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.store_tr = native_store_tr,
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.load_tls = native_load_tls,
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#ifdef CONFIG_X86_64
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.load_gs_index = native_load_gs_index,
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#endif
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.write_ldt_entry = native_write_ldt_entry,
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.write_gdt_entry = native_write_gdt_entry,
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.write_idt_entry = native_write_idt_entry,
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.alloc_ldt = paravirt_nop,
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.free_ldt = paravirt_nop,
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.load_sp0 = native_load_sp0,
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#if defined(CONFIG_X86_32)
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.irq_enable_sysexit = native_irq_enable_sysexit,
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#endif
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#ifdef CONFIG_X86_64
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#ifdef CONFIG_IA32_EMULATION
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.usergs_sysret32 = native_usergs_sysret32,
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#endif
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.usergs_sysret64 = native_usergs_sysret64,
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#endif
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.iret = native_iret,
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.swapgs = native_swapgs,
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.set_iopl_mask = native_set_iopl_mask,
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.io_delay = native_io_delay,
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.start_context_switch = paravirt_nop,
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.end_context_switch = paravirt_nop,
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};
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/* At this point, native_get/set_debugreg has real function entries */
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NOKPROBE_SYMBOL(native_get_debugreg);
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NOKPROBE_SYMBOL(native_set_debugreg);
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NOKPROBE_SYMBOL(native_load_idt);
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struct pv_apic_ops pv_apic_ops = {
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#ifdef CONFIG_X86_LOCAL_APIC
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.startup_ipi_hook = paravirt_nop,
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#endif
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};
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#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
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/* 32-bit pagetable entries */
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#define PTE_IDENT __PV_IS_CALLEE_SAVE(_paravirt_ident_32)
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#else
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/* 64-bit pagetable entries */
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#define PTE_IDENT __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
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#endif
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struct pv_mmu_ops pv_mmu_ops = {
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.read_cr2 = native_read_cr2,
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.write_cr2 = native_write_cr2,
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.read_cr3 = native_read_cr3,
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.write_cr3 = native_write_cr3,
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.flush_tlb_user = native_flush_tlb,
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.flush_tlb_kernel = native_flush_tlb_global,
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.flush_tlb_single = native_flush_tlb_single,
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.flush_tlb_others = native_flush_tlb_others,
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.pgd_alloc = __paravirt_pgd_alloc,
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.pgd_free = paravirt_nop,
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.alloc_pte = paravirt_nop,
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.alloc_pmd = paravirt_nop,
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.alloc_pud = paravirt_nop,
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.release_pte = paravirt_nop,
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.release_pmd = paravirt_nop,
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.release_pud = paravirt_nop,
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.set_pte = native_set_pte,
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.set_pte_at = native_set_pte_at,
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.set_pmd = native_set_pmd,
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.set_pmd_at = native_set_pmd_at,
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.pte_update = paravirt_nop,
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.pte_update_defer = paravirt_nop,
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.pmd_update = paravirt_nop,
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.pmd_update_defer = paravirt_nop,
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.ptep_modify_prot_start = __ptep_modify_prot_start,
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.ptep_modify_prot_commit = __ptep_modify_prot_commit,
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#if CONFIG_PGTABLE_LEVELS >= 3
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#ifdef CONFIG_X86_PAE
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.set_pte_atomic = native_set_pte_atomic,
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.pte_clear = native_pte_clear,
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.pmd_clear = native_pmd_clear,
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#endif
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.set_pud = native_set_pud,
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.pmd_val = PTE_IDENT,
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.make_pmd = PTE_IDENT,
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#if CONFIG_PGTABLE_LEVELS == 4
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.pud_val = PTE_IDENT,
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.make_pud = PTE_IDENT,
|
|
|
|
.set_pgd = native_set_pgd,
|
|
#endif
|
|
#endif /* CONFIG_PGTABLE_LEVELS >= 3 */
|
|
|
|
.pte_val = PTE_IDENT,
|
|
.pgd_val = PTE_IDENT,
|
|
|
|
.make_pte = PTE_IDENT,
|
|
.make_pgd = PTE_IDENT,
|
|
|
|
.dup_mmap = paravirt_nop,
|
|
.exit_mmap = paravirt_nop,
|
|
.activate_mm = paravirt_nop,
|
|
|
|
.lazy_mode = {
|
|
.enter = paravirt_nop,
|
|
.leave = paravirt_nop,
|
|
.flush = paravirt_nop,
|
|
},
|
|
|
|
.set_fixmap = native_set_fixmap,
|
|
};
|
|
|
|
EXPORT_SYMBOL_GPL(pv_time_ops);
|
|
EXPORT_SYMBOL (pv_cpu_ops);
|
|
EXPORT_SYMBOL (pv_mmu_ops);
|
|
EXPORT_SYMBOL_GPL(pv_apic_ops);
|
|
EXPORT_SYMBOL_GPL(pv_info);
|
|
EXPORT_SYMBOL (pv_irq_ops);
|