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Re: [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path

From Andy Lutomirski <luto@amacapital.net>
Newsgroups linux.kernel
Subject Re: [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path
Date 2015-09-03 19:30 +0200
Message-ID <q4GuM-1LD-59@gated-at.bofh.it> (permalink)
References <q42xj-3mq-3@gated-at.bofh.it> <q42xl-3mq-59@gated-at.bofh.it> <q4FS2-M8-17@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Thu, Sep 3, 2015 at 9:45 AM, Brian Gerst <brgerst@gmail.com> wrote:
> On Tue, Sep 1, 2015 at 6:41 PM, Andy Lutomirski <luto@kernel.org> wrote:
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> ---
>>  arch/x86/entry/entry_32.S | 34 +++++++++++++---------------------
>>  1 file changed, 13 insertions(+), 21 deletions(-)
>>
>> diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
>> index 36b6beb181f6..02881e528945 100644
>> --- a/arch/x86/entry/entry_32.S
>> +++ b/arch/x86/entry/entry_32.S
>> @@ -153,13 +153,13 @@
>>
>>  #endif /* CONFIG_X86_32_LAZY_GS */
>>
>> -.macro SAVE_ALL
>> +.macro SAVE_ALL pt_regs_ax=%eax
>>         cld
>>         PUSH_GS
>>         pushl   %fs
>>         pushl   %es
>>         pushl   %ds
>> -       pushl   %eax
>> +       pushl   \pt_regs_ax
>>         pushl   %ebp
>>         pushl   %edi
>>         pushl   %esi
>> @@ -370,20 +370,17 @@ ENDPROC(entry_SYSENTER_32)
>>         # system call handler stub
>>  ENTRY(entry_INT80_32)
>>         ASM_CLAC
>> -       pushl   %eax                            # save orig_eax
>> -       SAVE_ALL
>> -       GET_THREAD_INFO(%ebp)
>> -                                               # system call tracing in operation / emulation
>> -       testl   $_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
>> -       jnz     syscall_trace_entry
>> -       cmpl    $(NR_syscalls), %eax
>> -       jae     syscall_badsys
>> -syscall_call:
>> -       call    *sys_call_table(, %eax, 4)
>> -syscall_after_call:
>> -       movl    %eax, PT_EAX(%esp)              # store the return value
>> -syscall_exit:
>> -       jmp     syscall_exit_work
>> +       pushl   %eax                    /* pt_regs->orig_ax */
>> +       SAVE_ALL pt_regs_ax=$-ENOSYS    /* save rest, load -ENOSYS into ax */
>> +
>> +       /*
>> +        * User mode is traced as though IRQs are on, and the interrupt gate
>> +        * turned them off.
>> +        */
>> +       TRACE_IRQS_OFF
>> +
>> +       movl    %esp, %eax
>> +       call    do_int80_syscall_32
>>
>>  restore_all:
>>         TRACE_IRQS_IRET
>> @@ -491,11 +488,6 @@ syscall_fault:
>>         jmp     resume_userspace
>>  END(syscall_fault)
>>
>> -syscall_badsys:
>> -       movl    $-ENOSYS, %eax
>> -       jmp     syscall_after_call
>> -END(syscall_badsys)
>> -
>>  sysenter_badsys:
>>         movl    $-ENOSYS, %eax
>>         jmp     sysenter_after_call
>> --
>> 2.4.3
>>
>
> While bisecting a boot failure on the 32-bit native kernel I came
> across this build error:
> arch/x86/built-in.o: In function `syscall_trace_entry':
> /home/bgerst/kernel/linux/arch/x86/entry/entry_32.S:468: undefined
> reference to `syscall_call'
> /home/bgerst/kernel/linux/arch/x86/entry/entry_32.S:469: undefined
> reference to `syscall_exit'
>

Whoops!  I'll fix that up for v2.

--Andy
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Thread

[RFC 00/30] x86: Rewrite all syscall entries except native 64-bit Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 15/30] x86/entry/64/compat: Set up full pt_regs for all compat syscalls Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 21/30] x86/vdso/compat: Wire up SYSENTER and SYSCSALL for compat userspace Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 26/30] x86/asm: Remove thread_info.sysenter_return Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 27/30] x86/entry: Remove unnecessary IRQ twiddling in fast 32-bit syscalls Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 11/30] x86/vdso/32: Save extra registers in the INT80 vsyscall path Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 25/30] x86/entry/32: Re-implement SYSENTER using the new C path Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 30/30] x86/entry: Micro-optimize compat fast syscall arg fetch Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 14/30] x86/entry/64/compat: Remove most of the fast system call machinery Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 20/30] x86/entry: Add C code for fast system call entries Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 04/30] x86/entry: Move lockdep_sys_exit to prepare_exit_to_usermode Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 13/30] x86/entry/64/compat: Remove audit optimizations Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 06/30] x86/sched/64: Don't save flags on context switch (reinstated) Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 22/30] x86/entry/compat: Implement opportunistic SYSRETL for compat syscalls Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 16/30] x86/entry/syscalls: Move syscall table declarations into asm/syscalls.h Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 18/30] x86/entry: Add do_syscall_32, a C function to do 32-bit syscalls Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 28/30] x86/entry: Make irqs_disabled checks in exit code depend on lockdep Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 19/30] x86/entry/64/compat: Migrate the body of the syscall entry to C Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 23/30] x86/entry/32: Open-code return tracking from fork and kthreads Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 01/30] selftests/x86: Add a test for vDSO unwinding Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
    Re: [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path Brian Gerst <brgerst@gmail.com> - 2015-09-03 18:50 +0200
      Re: [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path Andy Lutomirski <luto@amacapital.net> - 2015-09-03 19:30 +0200
  [RFC 29/30] x86/entry: Force inlining of 32-bit syscall code Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 17/30] x86/syscalls: Give sys_call_ptr_t a useful type Andy Lutomirski <luto@kernel.org> - 2015-09-02 00:50 +0200
  [RFC 03/30] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  [RFC 05/30] x86/entry/64/compat: After SYSENTER, move STI after the NT fixup Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  [RFC 08/30] x86/asm: Re-add manual CFI infrastructure Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  [RFC 10/30] x86/vdso: Replace hex int80 CFI annotations with gas directives Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  [RFC 02/30] selftests/x86: Add a test for syscall restart and arg modification Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  [RFC 09/30] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm Andy Lutomirski <luto@kernel.org> - 2015-09-02 01:00 +0200
  Re: [RFC 00/30] x86: Rewrite all syscall entries except native 64-bit Brian Gerst <brgerst@gmail.com> - 2015-09-03 07:30 +0200
    Re: [RFC 00/30] x86: Rewrite all syscall entries except native 64-bit Andy Lutomirski <luto@amacapital.net> - 2015-09-03 19:20 +0200

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