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f1f029c7bf
From Gabe Black in bugzilla 13888:
native_save_fl is implemented as follows:
11static inline unsigned long native_save_fl(void)
12{
13 unsigned long flags;
14
15 asm volatile("# __raw_save_flags\n\t"
16 "pushf ; pop %0"
17 : "=g" (flags)
18 : /* no input */
19 : "memory");
20
21 return flags;
22}
If gcc chooses to put flags on the stack, for instance because this is
inlined into a larger function with more register pressure, the offset
of the flags variable from the stack pointer will change when the
pushf is performed. gcc doesn't attempt to understand that fact, and
address used for pop will still be the same. It will write to
somewhere near flags on the stack but not actually into it and
overwrite some other value.
I saw this happen in the ide_device_add_all function when running in a
simulator I work on. I'm assuming that some quirk of how the simulated
hardware is set up caused the code path this is on to be executed when
it normally wouldn't.
A simple fix might be to change "=g" to "=r".
Reported-by: Gabe Black <spamforgabe@umich.edu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Stable Team <stable@kernel.org>
218 lines
4.2 KiB
C
218 lines
4.2 KiB
C
#ifndef _X86_IRQFLAGS_H_
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#define _X86_IRQFLAGS_H_
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#include <asm/processor-flags.h>
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#ifndef __ASSEMBLY__
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/*
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* Interrupt control:
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*/
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static inline unsigned long native_save_fl(void)
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{
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unsigned long flags;
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/*
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* Note: this needs to be "=r" not "=rm", because we have the
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* stack offset from what gcc expects at the time the "pop" is
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* executed, and so a memory reference with respect to the stack
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* would end up using the wrong address.
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*/
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asm volatile("# __raw_save_flags\n\t"
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"pushf ; pop %0"
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: "=r" (flags)
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: /* no input */
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: "memory");
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return flags;
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}
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static inline void native_restore_fl(unsigned long flags)
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{
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asm volatile("push %0 ; popf"
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: /* no output */
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:"g" (flags)
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:"memory", "cc");
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}
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static inline void native_irq_disable(void)
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{
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asm volatile("cli": : :"memory");
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}
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static inline void native_irq_enable(void)
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{
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asm volatile("sti": : :"memory");
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}
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static inline void native_safe_halt(void)
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{
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asm volatile("sti; hlt": : :"memory");
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}
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static inline void native_halt(void)
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{
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asm volatile("hlt": : :"memory");
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}
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#endif
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#ifdef CONFIG_PARAVIRT
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#include <asm/paravirt.h>
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#else
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#ifndef __ASSEMBLY__
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static inline unsigned long __raw_local_save_flags(void)
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{
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return native_save_fl();
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}
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static inline void raw_local_irq_restore(unsigned long flags)
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{
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native_restore_fl(flags);
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}
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static inline void raw_local_irq_disable(void)
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{
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native_irq_disable();
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}
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static inline void raw_local_irq_enable(void)
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{
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native_irq_enable();
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}
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/*
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* Used in the idle loop; sti takes one instruction cycle
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* to complete:
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*/
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static inline void raw_safe_halt(void)
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{
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native_safe_halt();
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}
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/*
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* Used when interrupts are already enabled or to
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* shutdown the processor:
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*/
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static inline void halt(void)
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{
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native_halt();
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}
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/*
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* For spinlocks, etc:
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*/
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static inline unsigned long __raw_local_irq_save(void)
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{
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unsigned long flags = __raw_local_save_flags();
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raw_local_irq_disable();
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return flags;
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}
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#else
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#define ENABLE_INTERRUPTS(x) sti
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#define DISABLE_INTERRUPTS(x) cli
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#ifdef CONFIG_X86_64
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#define SWAPGS swapgs
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/*
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* Currently paravirt can't handle swapgs nicely when we
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* don't have a stack we can rely on (such as a user space
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* stack). So we either find a way around these or just fault
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* and emulate if a guest tries to call swapgs directly.
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*
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* Either way, this is a good way to document that we don't
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* have a reliable stack. x86_64 only.
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*/
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#define SWAPGS_UNSAFE_STACK swapgs
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#define PARAVIRT_ADJUST_EXCEPTION_FRAME /* */
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#define INTERRUPT_RETURN iretq
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#define USERGS_SYSRET64 \
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swapgs; \
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sysretq;
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#define USERGS_SYSRET32 \
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swapgs; \
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sysretl
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#define ENABLE_INTERRUPTS_SYSEXIT32 \
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swapgs; \
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sti; \
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sysexit
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#else
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#define INTERRUPT_RETURN iret
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#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
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#define GET_CR0_INTO_EAX movl %cr0, %eax
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* CONFIG_PARAVIRT */
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#ifndef __ASSEMBLY__
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#define raw_local_save_flags(flags) \
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do { (flags) = __raw_local_save_flags(); } while (0)
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#define raw_local_irq_save(flags) \
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do { (flags) = __raw_local_irq_save(); } while (0)
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static inline int raw_irqs_disabled_flags(unsigned long flags)
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{
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return !(flags & X86_EFLAGS_IF);
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}
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static inline int raw_irqs_disabled(void)
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{
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unsigned long flags = __raw_local_save_flags();
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return raw_irqs_disabled_flags(flags);
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}
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#else
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#ifdef CONFIG_X86_64
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#define ARCH_LOCKDEP_SYS_EXIT call lockdep_sys_exit_thunk
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#define ARCH_LOCKDEP_SYS_EXIT_IRQ \
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TRACE_IRQS_ON; \
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sti; \
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SAVE_REST; \
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LOCKDEP_SYS_EXIT; \
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RESTORE_REST; \
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cli; \
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TRACE_IRQS_OFF;
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#else
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#define ARCH_LOCKDEP_SYS_EXIT \
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pushl %eax; \
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pushl %ecx; \
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pushl %edx; \
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call lockdep_sys_exit; \
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popl %edx; \
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popl %ecx; \
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popl %eax;
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#define ARCH_LOCKDEP_SYS_EXIT_IRQ
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#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
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# define TRACE_IRQS_ON call trace_hardirqs_on_thunk;
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# define TRACE_IRQS_OFF call trace_hardirqs_off_thunk;
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#else
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# define TRACE_IRQS_ON
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# define TRACE_IRQS_OFF
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define LOCKDEP_SYS_EXIT ARCH_LOCKDEP_SYS_EXIT
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# define LOCKDEP_SYS_EXIT_IRQ ARCH_LOCKDEP_SYS_EXIT_IRQ
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# else
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# define LOCKDEP_SYS_EXIT
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# define LOCKDEP_SYS_EXIT_IRQ
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# endif
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#endif /* __ASSEMBLY__ */
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#endif
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