mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 09:45:08 +07:00
fbd704374d
This demotes an OOPS and likely panic due to a failed non-"safe" MSR access to a WARN_ONCE() and, for RDMSR, a return value of zero. To be clear, this type of failure should *not* happen. This patch exists to minimize the chance of nasty undebuggable failures happening when a CONFIG_PARAVIRT=y bug in the non-"safe" MSR helpers gets fixed. Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: KVM list <kvm@vger.kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: xen-devel <Xen-devel@lists.xen.org> Link: http://lkml.kernel.org/r/26567b216aae70e795938f4b567eace5a0eb90ba.1459605520.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
142 lines
3.4 KiB
C
142 lines
3.4 KiB
C
#include <linux/module.h>
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#include <asm/uaccess.h>
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#include <asm/traps.h>
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typedef bool (*ex_handler_t)(const struct exception_table_entry *,
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struct pt_regs *, int);
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static inline unsigned long
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ex_fixup_addr(const struct exception_table_entry *x)
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{
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return (unsigned long)&x->fixup + x->fixup;
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}
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static inline ex_handler_t
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ex_fixup_handler(const struct exception_table_entry *x)
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{
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return (ex_handler_t)((unsigned long)&x->handler + x->handler);
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}
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bool ex_handler_default(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr)
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{
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regs->ip = ex_fixup_addr(fixup);
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return true;
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}
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EXPORT_SYMBOL(ex_handler_default);
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bool ex_handler_fault(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr)
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{
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regs->ip = ex_fixup_addr(fixup);
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regs->ax = trapnr;
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return true;
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}
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EXPORT_SYMBOL_GPL(ex_handler_fault);
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bool ex_handler_ext(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr)
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{
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/* Special hack for uaccess_err */
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current_thread_info()->uaccess_err = 1;
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regs->ip = ex_fixup_addr(fixup);
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return true;
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}
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EXPORT_SYMBOL(ex_handler_ext);
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bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr)
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{
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WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n",
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(unsigned int)regs->cx);
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/* Pretend that the read succeeded and returned 0. */
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regs->ip = ex_fixup_addr(fixup);
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regs->ax = 0;
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regs->dx = 0;
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return true;
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}
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EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
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bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
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struct pt_regs *regs, int trapnr)
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{
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WARN_ONCE(1, "unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x)\n",
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(unsigned int)regs->cx,
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(unsigned int)regs->dx, (unsigned int)regs->ax);
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/* Pretend that the write succeeded. */
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regs->ip = ex_fixup_addr(fixup);
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return true;
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}
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EXPORT_SYMBOL(ex_handler_wrmsr_unsafe);
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bool ex_has_fault_handler(unsigned long ip)
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{
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const struct exception_table_entry *e;
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ex_handler_t handler;
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e = search_exception_tables(ip);
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if (!e)
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return false;
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handler = ex_fixup_handler(e);
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return handler == ex_handler_fault;
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}
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int fixup_exception(struct pt_regs *regs, int trapnr)
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{
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const struct exception_table_entry *e;
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ex_handler_t handler;
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#ifdef CONFIG_PNPBIOS
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if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
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extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
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extern u32 pnp_bios_is_utter_crap;
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pnp_bios_is_utter_crap = 1;
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printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
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__asm__ volatile(
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"movl %0, %%esp\n\t"
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"jmp *%1\n\t"
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: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
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panic("do_trap: can't hit this");
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}
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#endif
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e = search_exception_tables(regs->ip);
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if (!e)
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return 0;
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handler = ex_fixup_handler(e);
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return handler(e, regs, trapnr);
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}
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extern unsigned int early_recursion_flag;
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/* Restricted version used during very early boot */
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void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
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{
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/* Ignore early NMIs. */
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if (trapnr == X86_TRAP_NMI)
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return;
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if (early_recursion_flag > 2)
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goto halt_loop;
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if (regs->cs != __KERNEL_CS)
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goto fail;
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if (fixup_exception(regs, trapnr))
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return;
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fail:
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early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n",
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(unsigned)trapnr, (unsigned long)regs->cs, regs->ip,
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regs->orig_ax, read_cr2());
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show_regs(regs);
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halt_loop:
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while (true)
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halt();
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}
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