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SubjectRe: [PATCH V6 00/49] x86/entry/64: Convert a bunch of ASM entry code into C code
Hello Lai,

the patches in my point of view looks good. My qemue system boots with
this patches. From my side:

reviewed-by: damian.tomezki <dtometzki@fedoraproject.org>

best regards
Damian


On Fri, 26. Nov 18:11, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
>
> Changed from V5:
> Fix the code order of FENCE_SWAPGS_KERNEL_ENTRY in patch1 and
> change the new corresponding C entry code to match the asm code.
>
> Squash the patch of removing stack-protector from traps.c into
> a later patch that uses C entry code for #DB and #MCE
>
> Kill .Lgs_change and use the new asm_load_gs_index_gs_change in
> _ASM_EXTABLE
>
> s/ETNRY/ENTRY/g for DEFINE_IDTENTRY_IST_ENTRY macros
> ----
>
> 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 23 converts the error_entry() to C code. And patch 1-23
> are fixes and preparation for it.
>
> The patches 24-26 convert entry_INT80_compat and do cleanup.
>
> The patches 27-45 convert the IST entry code to C code. Many of them
> are preparation for the actual conversion.
>
> The patches 46-48 do cleanup.
>
> The patch 49 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
> error 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 misunderstanding
> 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.
>
> Changed from V4:
> Move FENCE_SWAPGS_KERNEL_ENTRY up in the patch1. And change the
> corresponding C code in later patches to keep coherence.
>
> Jmp to xenpv_restore_regs_and_return_to_usermode in
> swapgs_restore_regs_and_return_to_usermode instead of calling
> it everywhere.
>
> Add Miguel Ojeda's Reviewed-by.
>
> Changed from V3:
> Add a "Reviewed-by" for the xenpv fix
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>
> Change __attribute((__section__(section))) to __section(section)
>
> Move a part of ist_paranoid_exit() as a new ist_restore_gsbase()
>
> Add a new commit (patch 32) to change the ASM RESTORE_CR3, the
> corresponding C version ist_restore_cr3() is changed too.
>
> Changed from V2:
> Fix two places with missed FENCE_SWAPGS_KERNEL_ENTRY.
>
> Fix swapgs_restore_regs_and_return_to_usermode for XENPV.
>
> Updates the C entry_error()/parnoid_entry() to use
> fence_swapgs_kernel_entry when with user gsbase
> in kernel CR3.
>
> Simplify removing stack-protector in MAKEFILE.
>
> Squash commits about removing stack-protector in MAKEFILE.
>
> In V2 the C entry_error() checks xenpv first and uses natvie_swapgs
> but ASM entry_error() uses pv-aware SWAPGS. In V3, the
> commit is split into 3 commit, so the conversion has no
> semantic change.
>
> Move cld to the start of idtentry.
>
> Use idtentry macro for entry_INT80_compat and remove the old one.
>
> Add cleanup for PTI_USER_PGTABLE_BIT when it is moved to header
> file.
>
> Remove pv-aware SWAPGS.
>
> Changed from V1:
> Add a fix as the patch1. Found by trying to applied Peterz's
> suggestion in patch11.
> The whole entry_error() is converted to C instead of partial.
> The whole parnoid_entry() is converted to C instead of partial.
> The asm code of "parnoid_entry() cfunc() parnoid_exit()" are
> converted to C as suggested by Peterz.
> Add entry64.c rather than move traps.c to arch/x86/entry/
> The order of some commits is changed.
> Remove two cleanups
>
> [V1]: https://lore.kernel.org/all/20210831175025.27570-1-jiangshanlai@gmail.com/
> [V2]: https://lore.kernel.org/lkml/20210926150838.197719-1-jiangshanlai@gmail.com/
> [V3]: https://lore.kernel.org/lkml/20211014031413.14471-1-jiangshanlai@gmail.com/
> [V4]: https://lore.kernel.org/lkml/20211026141420.17138-1-jiangshanlai@gmail.com/
> [V5]: https://lore.kernel.org/lkml/20211110115736.3776-1-jiangshanlai@gmail.com/
>
> 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>
> Cc: Joerg Roedel <jroedel@suse.de>
>
> Lai Jiangshan (49):
> x86/entry: Add fence for kernel entry swapgs in paranoid_entry()
> x86/entry: Use the correct fence macro after swapgs in kernel CR3
> x86/xen: Add xenpv_restore_regs_and_return_to_usermode()
> x86/entry: Use swapgs and native_iret directly in
> swapgs_restore_regs_and_return_to_usermode
> compiler_types.h: Add __noinstr_section() for noinstr
> 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: Remove unused kernel_to_user_p4dp() and user_to_kernel_p4dp()
> x86: Replace PTI_PGTABLE_SWITCH_BIT with PTI_USER_PGTABLE_BIT
> x86: Mark __native_read_cr3() & native_write_cr3() as __always_inline
> x86/traps: Move the declaration of native_irq_return_iret into proto.h
> x86/entry: Add arch/x86/entry/entry64.c for C entry code
> x86/entry: Expose the address of .Lgs_change to entry64.c
> x86/entry: Add C verion of SWITCH_TO_KERNEL_CR3 as
> switch_to_kernel_cr3()
> x86/traps: Add fence_swapgs_{user,kernel}_entry()
> x86/entry: Add C user_entry_swapgs_and_fence()
> x86/traps: Move pt_regs only in fixup_bad_iret()
> x86/entry: Switch the stack after error_entry() returns
> x86/entry: move PUSH_AND_CLEAR_REGS out of error_entry
> x86/entry: Move cld to the start of idtentry
> x86/entry: Don't call error_entry for XENPV
> x86/entry: Convert SWAPGS to swapgs in error_entry()
> x86/entry: Implement the whole error_entry() as C code
> x86/entry: Use idtentry macro for entry_INT80_compat
> x86/entry: Convert SWAPGS to swapgs in entry_SYSENTER_compat()
> x86: Remove the definition of SWAPGS
> x86/entry: Make paranoid_exit() callable
> x86/entry: Call paranoid_exit() in asm_exc_nmi()
> x86/entry: move PUSH_AND_CLEAR_REGS out of paranoid_entry
> x86/entry: Add the C version ist_switch_to_kernel_cr3()
> x86/entry: Skip CR3 write when the saved CR3 is kernel CR3 in
> RESTORE_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 the C version ist_paranoid_entry()
> x86/entry: Implement the C version ist_paranoid_exit()
> x86/entry: Add a C macro to define the function body for IST in
> .entry.text
> x86/debug, mce: Use C entry code
> x86/idtentry.h: Move the definitions *IDTENTRY_{MCE|DEBUG}* up
> x86/nmi: Use DEFINE_IDTENTRY_NMI for nmi
> x86/nmi: Use C entry code
> x86/entry: Add a C macro to define the function body for IST in
> .entry.text with an error code
> x86/doublefault: Use C entry code
> x86/sev: Add and use ist_vc_switch_off_ist()
> x86/sev: Use C entry code
> x86/entry: Remove ASM function paranoid_entry() and paranoid_exit()
> x86/entry: Remove the unused ASM macros
> x86/entry: Remove save_ret from PUSH_AND_CLEAR_REGS
> x86/syscall/64: Move the checking for sysret to C code
>
> arch/x86/entry/Makefile | 3 +-
> arch/x86/entry/calling.h | 142 +-------
> arch/x86/entry/common.c | 73 +++-
> arch/x86/entry/entry64.c | 348 +++++++++++++++++++
> arch/x86/entry/entry_64.S | 448 ++++---------------------
> arch/x86/entry/entry_64_compat.S | 104 +-----
> arch/x86/include/asm/idtentry.h | 111 +++++-
> arch/x86/include/asm/irqflags.h | 8 -
> arch/x86/include/asm/pgtable.h | 23 +-
> arch/x86/include/asm/processor-flags.h | 15 +
> arch/x86/include/asm/proto.h | 5 +-
> arch/x86/include/asm/special_insns.h | 4 +-
> arch/x86/include/asm/syscall.h | 2 +-
> arch/x86/include/asm/traps.h | 6 +-
> arch/x86/kernel/Makefile | 3 +
> arch/x86/kernel/cpu/mce/Makefile | 3 +
> arch/x86/kernel/nmi.c | 2 +-
> arch/x86/kernel/traps.c | 33 +-
> arch/x86/xen/xen-asm.S | 20 ++
> include/linux/compiler_types.h | 8 +-
> 20 files changed, 677 insertions(+), 684 deletions(-)
> create mode 100644 arch/x86/entry/entry64.c
>
> --
> 2.19.1.6.gb485710b
>

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