7f2590a110b8("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")
has resulted that when exception on userspace, the kernel (error_entry)
always push the pt_regs to entry stack(sp0), and then copy them to the
kernel stack.This is a hot path (for example page fault) and interrupt_entry directly switches to kernel stack and pushes pt_regs to kernel stack. We should do it for error_entry. This is the job of patch1,2. Patch 3-5 simply stack switching for .Lerror_bad_iret by just doing all the work in one function (fixup_bad_iret()). The patch set is based on tip/master (c021d3d8fe45) (Mon May 25). The diffstat is "66 insertions(+), 66 deletions(-)", but actually it mainly adds comments and deletes code. Cc: Andy Lutomirski <[email protected]>, Cc: Thomas Gleixner <[email protected]>, Cc: Ingo Molnar <[email protected]>, Cc: Borislav Petkov <[email protected]>, Cc: [email protected], Cc: "H. Peter Anvin" <[email protected]>, Cc: Peter Zijlstra <[email protected]>, Cc: Alexandre Chartre <[email protected]>, Cc: "Eric W. Biederman" <[email protected]>, Cc: Jann Horn <[email protected]>, Cc: Dave Hansen <[email protected]> Lai Jiangshan (5): x86/entry: introduce macro idtentry_swapgs_and_switch_to_kernel_stack x86/entry: avoid calling into sync_regs() when entering from userspace x86/entry: directly switch to kernel stack when .Lerror_bad_iret x86/entry: remove unused sync_regs() x86/entry: don't copy to tmp in fixup_bad_iret arch/x86/entry/entry_64.S | 89 ++++++++++++++++++++---------------- arch/x86/include/asm/traps.h | 1 - arch/x86/kernel/traps.c | 42 +++++++---------- 3 files changed, 66 insertions(+), 66 deletions(-) -- 2.20.1
