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    Subject[RFC v2 PATCH 1/7] x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions
    Date
    All current code paths call SAVE_C_REGS and then immediately
    SAVE_EXTRA_REGS. Therefore, merge these two macros and order the MOV
    sequeneces properly.

    While at it, remove the macros to save all except specific registers,
    as these macros have been unused for a long time.

    Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    arch/x86/entry/calling.h | 57 +++++++++++++----------------------------------
    arch/x86/entry/entry_64.S | 12 ++++------
    2 files changed, 19 insertions(+), 50 deletions(-)

    diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
    index f4b129d4af42..8907a6593b42 100644
    --- a/arch/x86/entry/calling.h
    +++ b/arch/x86/entry/calling.h
    @@ -101,49 +101,22 @@ For 32-bit we have the following conventions - kernel is built with
    addq $-(15*8), %rsp
    .endm

    - .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
    - .if \r11
    - movq %r11, 6*8+\offset(%rsp)
    - .endif
    - .if \r8910
    - movq %r10, 7*8+\offset(%rsp)
    - movq %r9, 8*8+\offset(%rsp)
    - movq %r8, 9*8+\offset(%rsp)
    - .endif
    - .if \rax
    - movq %rax, 10*8+\offset(%rsp)
    - .endif
    - .if \rcx
    - movq %rcx, 11*8+\offset(%rsp)
    - .endif
    - movq %rdx, 12*8+\offset(%rsp)
    - movq %rsi, 13*8+\offset(%rsp)
    + .macro SAVE_REGS offset=0
    movq %rdi, 14*8+\offset(%rsp)
    - UNWIND_HINT_REGS offset=\offset extra=0
    - .endm
    - .macro SAVE_C_REGS offset=0
    - SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
    - .endm
    - .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
    - SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
    - .endm
    - .macro SAVE_C_REGS_EXCEPT_R891011
    - SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
    - .endm
    - .macro SAVE_C_REGS_EXCEPT_RCX_R891011
    - SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
    - .endm
    - .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
    - SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
    - .endm
    -
    - .macro SAVE_EXTRA_REGS offset=0
    - movq %r15, 0*8+\offset(%rsp)
    - movq %r14, 1*8+\offset(%rsp)
    - movq %r13, 2*8+\offset(%rsp)
    - movq %r12, 3*8+\offset(%rsp)
    - movq %rbp, 4*8+\offset(%rsp)
    + movq %rsi, 13*8+\offset(%rsp)
    + movq %rdx, 12*8+\offset(%rsp)
    + movq %rcx, 11*8+\offset(%rsp)
    + movq %rax, 10*8+\offset(%rsp)
    + movq %r8, 9*8+\offset(%rsp)
    + movq %r9, 8*8+\offset(%rsp)
    + movq %r10, 7*8+\offset(%rsp)
    + movq %r11, 6*8+\offset(%rsp)
    movq %rbx, 5*8+\offset(%rsp)
    + movq %rbp, 4*8+\offset(%rsp)
    + movq %r12, 3*8+\offset(%rsp)
    + movq %r13, 2*8+\offset(%rsp)
    + movq %r14, 1*8+\offset(%rsp)
    + movq %r15, 0*8+\offset(%rsp)
    UNWIND_HINT_REGS offset=\offset
    .endm

    @@ -197,7 +170,7 @@ For 32-bit we have the following conventions - kernel is built with
    * is just setting the LSB, which makes it an invalid stack address and is also
    * a signal to the unwinder that it's a pt_regs pointer in disguise.
    *
    - * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
    + * NOTE: This macro must be used *after* SAVE_REGS because it corrupts
    * the original rbp.
    */
    .macro ENCODE_FRAME_POINTER ptregs_offset=0
    diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    index 9e48002b953b..91e8d84c2496 100644
    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -573,8 +573,7 @@ END(irq_entries_start)
    1:

    ALLOC_PT_GPREGS_ON_STACK
    - SAVE_C_REGS
    - SAVE_EXTRA_REGS
    + SAVE_REGS
    CLEAR_REGS_NOSPEC
    ENCODE_FRAME_POINTER

    @@ -1132,8 +1131,7 @@ ENTRY(xen_failsafe_callback)
    UNWIND_HINT_IRET_REGS
    pushq $-1 /* orig_ax = -1 => not a system call */
    ALLOC_PT_GPREGS_ON_STACK
    - SAVE_C_REGS
    - SAVE_EXTRA_REGS
    + SAVE_REGS
    CLEAR_REGS_NOSPEC
    ENCODE_FRAME_POINTER
    jmp error_exit
    @@ -1178,8 +1176,7 @@ idtentry machine_check do_mce has_error_code=0 paranoid=1
    ENTRY(paranoid_entry)
    UNWIND_HINT_FUNC
    cld
    - SAVE_C_REGS 8
    - SAVE_EXTRA_REGS 8
    + SAVE_REGS 8
    CLEAR_REGS_NOSPEC
    ENCODE_FRAME_POINTER 8
    movl $1, %ebx
    @@ -1231,8 +1228,7 @@ END(paranoid_exit)
    ENTRY(error_entry)
    UNWIND_HINT_FUNC
    cld
    - SAVE_C_REGS 8
    - SAVE_EXTRA_REGS 8
    + SAVE_REGS 8
    CLEAR_REGS_NOSPEC
    ENCODE_FRAME_POINTER 8
    testb $3, CS+8(%rsp)
    --
    2.16.1
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