Messages in this thread | | | From | Lai Jiangshan <> | Subject | [PATCH 00/24] x86/entry/64: Convert a bunch of ASM entry code into C code | Date | Wed, 1 Sep 2021 01:50:01 +0800 |
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From: Lai Jiangshan <laijs@linux.alibaba.com>
Many ASM code in entry_64.S can be rewritten in C if they can be written to be non-instrumentable and are called in the right order regarding to whether CR3/gsbase is changed to kernel CR3/gsbase.
The patchset covert some of them to C code.
The patch 11 converts the non paranoid entry (entry of interrupts/ non-IST-exception/IST-exception-from-user) to C code. And patch 1-10 are preparation for it and patch 12-13 are cleanup for it. The patch 1 might fix a defect.
The patch 22 converts the paranoid entry/exit to Code. And patch 14-21 are pareparation for it and patch 23 is cleanup for it.
The patch 24 converts a small part of ASM code of syscall to C code which does the checking for whether it can use sysret to return to userspace.
Some other paths can be possible to be in C code, for example: the non paranoid exit, the syscall entry/exit. The PTI handling for them can be in C code. But it would required the pt_regs to be copied/pushed to the entry stack which means the C code would not be efficient.
When converting ASM to C, the most effort is to make them the same. Almost no creative was involved. The code are kept as the same as ASM as possible and no functional change intended unless my missunderstanding in the ASM code was involved. The functions called by the C entry code are checked to be ensured noinstr or __always_inline. Some of them have more than one definitions and require some more cares from reviewers. The comments in the ASM are also copied in the right place in the C code.
Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Lai Jiangshan (24): x86/traps: Remove stack-protector from traps.c x86/traps: Move arch/x86/kernel/traps.c to arch/x86/entry/ x86/traps: Move declaration of native_irq_return_iret up x86/entry: Expose the address of .Lgs_change to traps.c x86/entry: Introduce __entry_text for entry code written in C x86/entry: Move PTI_USER_* to arch/x86/include/asm/processor-flags.h x86: Mark __native_read_cr3() & native_write_cr3() as __always_inline x86/traps: Add C verion of SWITCH_TO_KERNEL_CR3 as switch_to_kernel_cr3() x86/traps: Add fence_swapgs_{user,kernel}_entry() x86/traps: Move pt_regs only in fixup_bad_iret() x86/entry: Replace the most of asm code of error_entry to C code x86/traps: Reconstruct pt_regs on task stack directly in fixup_bad_iret() x86/traps: Mark sync_regs() and fixup_bad_iret() as static __always_inline x86/entry: Make paranoid_exit() callable x86/entry: Call paranoid_exit() in asm_exc_nmi() x86/entry: Use skip_rdi instead of save_ret for PUSH_AND_CLEAR_REGS x86/entry: Introduce struct ist_regs x86/entry: Add the C version ist_switch_to_kernel_cr3() x86/entry: Add the C version ist_restore_cr3() x86/entry: Add the C version get_percpu_base() x86/entry: Add the C version ist_switch_to_kernel_gsbase() x86/entry: Implement and use do_paranoid_entry() and paranoid_exit() x86/entry: Remove the unused ASM macros x86/syscall/64: Move the checking for sysret to C code
arch/x86/entry/Makefile | 5 +- arch/x86/entry/calling.h | 144 +-------- arch/x86/entry/common.c | 73 ++++- arch/x86/entry/entry_64.S | 366 ++++------------------- arch/x86/{kernel => entry}/traps.c | 397 +++++++++++++++++++++++-- arch/x86/include/asm/processor-flags.h | 15 + arch/x86/include/asm/special_insns.h | 4 +- arch/x86/include/asm/syscall.h | 2 +- arch/x86/include/asm/traps.h | 36 ++- arch/x86/kernel/Makefile | 2 +- arch/x86/kernel/asm-offsets_64.c | 2 + 11 files changed, 554 insertions(+), 492 deletions(-) rename arch/x86/{kernel => entry}/traps.c (74%)
-- 2.19.1.6.gb485710b
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