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

--
Brian Gerst


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