When I rewrote entry_INT80_32, I thought that int80 was an interrupt gate. It's a trap gate. *facepalm*
Thanks to Brian Gerst for pointing out that it's better to change the entry code than to change the gate type. Suggested-by: Brian Gerst <[email protected]> Reported-by: Borislav Petkov <[email protected]> Fixes: 150ac78d63af ("x86/entry/32: Switch INT80 to the new C syscall path") Signed-off-by: Andy Lutomirski <[email protected]> --- arch/x86/entry/common.c | 15 ++++++++++++--- arch/x86/entry/entry_32.S | 8 ++++---- arch/x86/entry/entry_64_compat.S | 2 +- 3 files changed, 17 insertions(+), 8 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index b53e04d301a3..09afb3b6acbb 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -351,7 +351,14 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs) * in workloads that use it, and it's usually called from * do_fast_syscall_32, so forcibly inline it to improve performance. */ -static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) +#ifdef CONFIG_X86_32 +/* 32-bit kernels use a trap gate for int80, and the asm code calls here. */ +__visible +#else +/* 64-bit kernels use do_syscall_32_irqs_off instead. */ +static +#endif +__always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) { struct thread_info *ti = pt_regs_to_thread_info(regs); unsigned int nr = (unsigned int)regs->orig_ax; @@ -386,12 +393,14 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) syscall_return_slowpath(regs); } -/* Handles int $0x80 */ -__visible void do_int80_syscall_32(struct pt_regs *regs) +#ifdef CONFIG_X86_64 +/* Handles int $0x80 on 64-bit kernels */ +__visible void do_syscall_32_irqs_off(struct pt_regs *regs) { local_irq_enable(); do_syscall_32_irqs_on(regs); } +#endif /* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */ __visible long do_fast_syscall_32(struct pt_regs *regs) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 07a041b91af1..ba0dad937be9 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -346,13 +346,13 @@ ENTRY(entry_INT80_32) SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */ /* - * User mode is traced as though IRQs are on, and the interrupt gate - * turned them off. + * User mode is traced as though IRQs are on. Unlike the 64-bit + * case, int80 is a trap gate on 32-bit kernels, so interrupts + * are already on (unless user code is messing around with iopl). */ - TRACE_IRQS_OFF movl %esp, %eax - call do_int80_syscall_32 + call do_syscall_32_irqs_on .Lsyscall_32_done: restore_all: diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 78becafe60d1..dd160e4e2ef5 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -303,7 +303,7 @@ ENTRY(entry_INT80_compat) TRACE_IRQS_OFF movq %rsp, %rdi - call do_int80_syscall_32 + call do_syscall_32_irqs_off .Lsyscall_32_done: /* Go back to user mode. */ -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
