Re: [PATCH 2/6] x86: entry_64.S: move save_paranoid and ret_from_fork closer to their users

[Andy Lutomirski]

On Mon, Feb 23, 2015 at 4:12 PM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
> For some odd reason, these two functions are at the very top of the file.
> save_paranoid's caller is approximately in the middle of it, move it there.
> Move ret_from_fork to be right after fork/exec helpers.
>
> This is a pure block move, nothing is changed in the function bodies.

Applied.

>
> Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Oleg Nesterov <oleg@xxxxxxxxxx>
> CC: Borislav Petkov <bp@xxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> CC: X86 ML <x86@xxxxxxxxxx>
> CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
> CC: Will Drewry <wad@xxxxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  arch/x86/kernel/entry_64.S | 106 ++++++++++++++++++++++-----------------------
>  1 file changed, 53 insertions(+), 53 deletions(-)
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 63e7ccd..71b549a 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -202,59 +202,6 @@ ENDPROC(native_usergs_sysret64)
>         CFI_REL_OFFSET r15, R15+\offset
>         .endm
>
> -ENTRY(save_paranoid)
> -       XCPT_FRAME 1 RDI+8
> -       cld
> -       SAVE_C_REGS 8
> -       SAVE_EXTRA_REGS 8
> -       movl $1,%ebx
> -       movl $MSR_GS_BASE,%ecx
> -       rdmsr
> -       testl %edx,%edx
> -       js 1f   /* negative -> in kernel */
> -       SWAPGS
> -       xorl %ebx,%ebx
> -1:     ret
> -       CFI_ENDPROC
> -END(save_paranoid)
> -
> -/*
> - * A newly forked process directly context switches into this address.
> - *
> - * rdi: prev task we switched from
> - */
> -ENTRY(ret_from_fork)
> -       DEFAULT_FRAME
> -
> -       LOCK ; btr $TIF_FORK,TI_flags(%r8)
> -
> -       pushq_cfi $0x0002
> -       popfq_cfi                               # reset kernel eflags
> -
> -       call schedule_tail                      # rdi: 'prev' task parameter
> -
> -       GET_THREAD_INFO(%rcx)
> -
> -       RESTORE_EXTRA_REGS
> -
> -       testl $3,CS(%rsp)                       # from kernel_thread?
> -       jz   1f
> -
> -       testl $_TIF_IA32, TI_flags(%rcx)        # 32-bit compat task needs IRET
> -       jnz  int_ret_from_sys_call
> -
> -       RESTORE_TOP_OF_STACK %rdi
> -       jmp ret_from_sys_call                   # go to the SYSRET fastpath
> -
> -1:
> -       movq %rbp, %rdi
> -       call *%rbx
> -       movl $0, RAX(%rsp)
> -       RESTORE_EXTRA_REGS
> -       jmp int_ret_from_sys_call
> -       CFI_ENDPROC
> -END(ret_from_fork)
> -
>  /*
>   * 64bit SYSCALL instruction entry. Up to 6 arguments in registers.
>   *
> @@ -581,6 +528,43 @@ END(stub_x32_execveat)
>  #endif
>
>  /*
> + * A newly forked process directly context switches into this address.
> + *
> + * rdi: prev task we switched from
> + */
> +ENTRY(ret_from_fork)
> +       DEFAULT_FRAME
> +
> +       LOCK ; btr $TIF_FORK,TI_flags(%r8)
> +
> +       pushq_cfi $0x0002
> +       popfq_cfi                               # reset kernel eflags
> +
> +       call schedule_tail                      # rdi: 'prev' task parameter
> +
> +       GET_THREAD_INFO(%rcx)
> +
> +       RESTORE_EXTRA_REGS
> +
> +       testl $3,CS(%rsp)                       # from kernel_thread?
> +       jz   1f
> +
> +       testl $_TIF_IA32, TI_flags(%rcx)        # 32-bit compat task needs IRET
> +       jnz  int_ret_from_sys_call
> +
> +       RESTORE_TOP_OF_STACK %rdi
> +       jmp ret_from_sys_call                   # go to the SYSRET fastpath
> +
> +1:
> +       movq %rbp, %rdi
> +       call *%rbx
> +       movl $0, RAX(%rsp)
> +       RESTORE_EXTRA_REGS
> +       jmp int_ret_from_sys_call
> +       CFI_ENDPROC
> +END(ret_from_fork)
> +
> +/*
>   * Build the entry stubs and pointer table with some assembler magic.
>   * We pack 7 stubs into a single 32-byte chunk, which will fit in a
>   * single cache line on all modern x86 implementations.
> @@ -1269,6 +1253,22 @@ idtentry async_page_fault do_async_page_fault has_error_code=1
>  idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
>  #endif
>
> +ENTRY(save_paranoid)
> +       XCPT_FRAME 1 RDI+8
> +       cld
> +       SAVE_C_REGS 8
> +       SAVE_EXTRA_REGS 8
> +       movl $1,%ebx
> +       movl $MSR_GS_BASE,%ecx
> +       rdmsr
> +       testl %edx,%edx
> +       js 1f   /* negative -> in kernel */
> +       SWAPGS
> +       xorl %ebx,%ebx
> +1:     ret
> +       CFI_ENDPROC
> +END(save_paranoid)
> +
>         /*
>          * "Paranoid" exit path from exception stack.  This is invoked
>          * only on return from non-NMI IST interrupts that came
> --
> 1.8.1.4
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/