diff options
Diffstat (limited to 'arch/x86/entry/common.c')
| -rw-r--r-- | arch/x86/entry/common.c | 37 |
1 files changed, 36 insertions, 1 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 8ca4d57d68eb..6356060caaf3 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -26,6 +26,7 @@ #include <xen/events.h> #endif +#include <asm/apic.h> #include <asm/desc.h> #include <asm/traps.h> #include <asm/vdso.h> @@ -168,6 +169,25 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr) } #ifdef CONFIG_IA32_EMULATION +static __always_inline bool int80_is_external(void) +{ + const unsigned int offs = (0x80 / 32) * 0x10; + const u32 bit = BIT(0x80 % 32); + + /* The local APIC on XENPV guests is fake */ + if (cpu_feature_enabled(X86_FEATURE_XENPV)) + return false; + + /* + * If vector 0x80 is set in the APIC ISR then this is an external + * interrupt. Either from broken hardware or injected by a VMM. + * + * Note: In guest mode this is only valid for secure guests where + * the secure module fully controls the vAPIC exposed to the guest. + */ + return apic_read(APIC_ISR + offs) & bit; +} + /** * int80_emulation - 32-bit legacy syscall entry * @@ -191,12 +211,27 @@ DEFINE_IDTENTRY_RAW(int80_emulation) { int nr; - /* Establish kernel context. */ + /* Kernel does not use INT $0x80! */ + if (unlikely(!user_mode(regs))) { + irqentry_enter(regs); + instrumentation_begin(); + panic("Unexpected external interrupt 0x80\n"); + } + + /* + * Establish kernel context for instrumentation, including for + * int80_is_external() below which calls into the APIC driver. + * Identical for soft and external interrupts. + */ enter_from_user_mode(regs); instrumentation_begin(); add_random_kstack_offset(); + /* Validate that this is a soft interrupt to the extent possible */ + if (unlikely(int80_is_external())) + panic("Unexpected external interrupt 0x80\n"); + /* * The low level idtentry code pushed -1 into regs::orig_ax * and regs::ax contains the syscall number. |