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SubjectRe: [PATCH 2/6] x86: entry_64.S: move save_paranoid and ret_from_fork closer to their users
On Mon, Feb 23, 2015 at 4:12 PM, Denys Vlasenko <dvlasenk@redhat.com> 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@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: X86 ML <x86@kernel.org>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: linux-kernel@vger.kernel.org
> ---
> 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


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