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x86_64, traps: Fix the espfix64 #DF fixup and rewrite it in C
There's nothing special enough about the espfix64 double fault fixup to
justify writing it in assembly. Move it to C.
This also fixes a bug: if the double fault came from an IST stack, the
old asm code would return to a partially uninitialized stack frame.
Fixes: 3891a04aaf
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
fc14f9c127
commit
af726f21ed
2 changed files with 26 additions and 32 deletions
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@ -828,6 +828,7 @@ ENTRY(native_iret)
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jnz native_irq_return_ldt
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#endif
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.global native_irq_return_iret
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native_irq_return_iret:
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iretq
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_ASM_EXTABLE(native_irq_return_iret, bad_iret)
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@ -922,37 +923,6 @@ ENTRY(retint_kernel)
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CFI_ENDPROC
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END(common_interrupt)
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/*
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* If IRET takes a fault on the espfix stack, then we
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* end up promoting it to a doublefault. In that case,
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* modify the stack to make it look like we just entered
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* the #GP handler from user space, similar to bad_iret.
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*/
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#ifdef CONFIG_X86_ESPFIX64
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ALIGN
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__do_double_fault:
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XCPT_FRAME 1 RDI+8
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movq RSP(%rdi),%rax /* Trap on the espfix stack? */
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sarq $PGDIR_SHIFT,%rax
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cmpl $ESPFIX_PGD_ENTRY,%eax
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jne do_double_fault /* No, just deliver the fault */
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cmpl $__KERNEL_CS,CS(%rdi)
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jne do_double_fault
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movq RIP(%rdi),%rax
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cmpq $native_irq_return_iret,%rax
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jne do_double_fault /* This shouldn't happen... */
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movq PER_CPU_VAR(kernel_stack),%rax
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subq $(6*8-KERNEL_STACK_OFFSET),%rax /* Reset to original stack */
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movq %rax,RSP(%rdi)
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movq $0,(%rax) /* Missing (lost) #GP error code */
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movq $general_protection,RIP(%rdi)
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retq
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CFI_ENDPROC
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END(__do_double_fault)
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#else
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# define __do_double_fault do_double_fault
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#endif
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/*
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* APIC interrupts.
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*/
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@ -1124,7 +1094,7 @@ idtentry overflow do_overflow has_error_code=0
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idtentry bounds do_bounds has_error_code=0
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idtentry invalid_op do_invalid_op has_error_code=0
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idtentry device_not_available do_device_not_available has_error_code=0
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idtentry double_fault __do_double_fault has_error_code=1 paranoid=1
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idtentry double_fault do_double_fault has_error_code=1 paranoid=1
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idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0
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idtentry invalid_TSS do_invalid_TSS has_error_code=1
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idtentry segment_not_present do_segment_not_present has_error_code=1
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@ -259,6 +259,30 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
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static const char str[] = "double fault";
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struct task_struct *tsk = current;
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#ifdef CONFIG_X86_ESPFIX64
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extern unsigned char native_irq_return_iret[];
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/*
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* If IRET takes a non-IST fault on the espfix64 stack, then we
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* end up promoting it to a doublefault. In that case, modify
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* the stack to make it look like we just entered the #GP
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* handler from user space, similar to bad_iret.
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*/
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if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
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regs->cs == __KERNEL_CS &&
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regs->ip == (unsigned long)native_irq_return_iret)
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{
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struct pt_regs *normal_regs = task_pt_regs(current);
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/* Fake a #GP(0) from userspace. */
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memmove(&normal_regs->ip, (void *)regs->sp, 5*8);
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normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */
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regs->ip = (unsigned long)general_protection;
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regs->sp = (unsigned long)&normal_regs->orig_ax;
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return;
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}
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#endif
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exception_enter();
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/* Return not checked because double check cannot be ignored */
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notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
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