Re: [PATCH 2/6] ftrace/x86_32: Move the ftrace specific code out of entry_32.S

[Namhyung Kim]

Hi Steve,

On Wed, Mar 22, 2017 at 10:35 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
>
> The function tracing hook code for ftrace is not an entry point from
> userspace and does not belong in the entry_*.S files. It has already been
> moved out of entry_64.S. This moves it out of entry_32.S into its own
> ftrace_32.S file.
>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> ---

[SNIP]
> diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
> new file mode 100644
> index 000000000000..1889a74823ce
> --- /dev/null
> +++ b/arch/x86/kernel/ftrace_32.S
> @@ -0,0 +1,177 @@
> +/*
> + *  linux/arch/x86_64/mcount_64.S

You may want to change this line.. :)

Thanks,
Namhyung


> + *
> + *  Copyright (C) 2017  Steven Rostedt, VMware Inc.
> + */
> +
> +#include <linux/linkage.h>
> +#include <asm/page_types.h>
> +#include <asm/segment.h>
> +#include <asm/export.h>
> +#include <asm/ftrace.h>
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +
> +ENTRY(mcount)
> +       ret
> +END(mcount)
> +
> +ENTRY(ftrace_caller)
> +       pushl   %eax
> +       pushl   %ecx
> +       pushl   %edx
> +       pushl   $0                              /* Pass NULL as regs pointer */
> +       movl    4*4(%esp), %eax
> +       movl    0x4(%ebp), %edx
> +       movl    function_trace_op, %ecx
> +       subl    $MCOUNT_INSN_SIZE, %eax
> +
> +.globl ftrace_call
> +ftrace_call:
> +       call    ftrace_stub
> +
> +       addl    $4, %esp                        /* skip NULL pointer */
> +       popl    %edx
> +       popl    %ecx
> +       popl    %eax
> +.Lftrace_ret:
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +.globl ftrace_graph_call
> +ftrace_graph_call:
> +       jmp     ftrace_stub
> +#endif
> +
> +/* This is weak to keep gas from relaxing the jumps */
> +WEAK(ftrace_stub)
> +       ret
> +END(ftrace_caller)
> +
> +ENTRY(ftrace_regs_caller)
> +       pushf   /* push flags before compare (in cs location) */
> +
> +       /*
> +        * i386 does not save SS and ESP when coming from kernel.
> +        * Instead, to get sp, &regs->sp is used (see ptrace.h).
> +        * Unfortunately, that means eflags must be at the same location
> +        * as the current return ip is. We move the return ip into the
> +        * ip location, and move flags into the return ip location.
> +        */
> +       pushl   4(%esp)                         /* save return ip into ip slot */
> +
> +       pushl   $0                              /* Load 0 into orig_ax */
> +       pushl   %gs
> +       pushl   %fs
> +       pushl   %es
> +       pushl   %ds
> +       pushl   %eax
> +       pushl   %ebp
> +       pushl   %edi
> +       pushl   %esi
> +       pushl   %edx
> +       pushl   %ecx
> +       pushl   %ebx
> +
> +       movl    13*4(%esp), %eax                /* Get the saved flags */
> +       movl    %eax, 14*4(%esp)                /* Move saved flags into regs->flags location */
> +                                               /* clobbering return ip */
> +       movl    $__KERNEL_CS, 13*4(%esp)
> +
> +       movl    12*4(%esp), %eax                /* Load ip (1st parameter) */
> +       subl    $MCOUNT_INSN_SIZE, %eax         /* Adjust ip */
> +       movl    0x4(%ebp), %edx                 /* Load parent ip (2nd parameter) */
> +       movl    function_trace_op, %ecx         /* Save ftrace_pos in 3rd parameter */
> +       pushl   %esp                            /* Save pt_regs as 4th parameter */
> +
> +GLOBAL(ftrace_regs_call)
> +       call    ftrace_stub
> +
> +       addl    $4, %esp                        /* Skip pt_regs */
> +       movl    14*4(%esp), %eax                /* Move flags back into cs */
> +       movl    %eax, 13*4(%esp)                /* Needed to keep addl  from modifying flags */
> +       movl    12*4(%esp), %eax                /* Get return ip from regs->ip */
> +       movl    %eax, 14*4(%esp)                /* Put return ip back for ret */
> +
> +       popl    %ebx
> +       popl    %ecx
> +       popl    %edx
> +       popl    %esi
> +       popl    %edi
> +       popl    %ebp
> +       popl    %eax
> +       popl    %ds
> +       popl    %es
> +       popl    %fs
> +       popl    %gs
> +       addl    $8, %esp                        /* Skip orig_ax and ip */
> +       popf                                    /* Pop flags at end (no addl to corrupt flags) */
> +       jmp     .Lftrace_ret
> +
> +       popf
> +       jmp     ftrace_stub
> +#else /* ! CONFIG_DYNAMIC_FTRACE */
> +
> +ENTRY(mcount)
> +       cmpl    $__PAGE_OFFSET, %esp
> +       jb      ftrace_stub                     /* Paging not enabled yet? */
> +
> +       cmpl    $ftrace_stub, ftrace_trace_function
> +       jnz     .Ltrace
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +       cmpl    $ftrace_stub, ftrace_graph_return
> +       jnz     ftrace_graph_caller
> +
> +       cmpl    $ftrace_graph_entry_stub, ftrace_graph_entry
> +       jnz     ftrace_graph_caller
> +#endif
> +.globl ftrace_stub
> +ftrace_stub:
> +       ret
> +
> +       /* taken from glibc */
> +.Ltrace:
> +       pushl   %eax
> +       pushl   %ecx
> +       pushl   %edx
> +       movl    0xc(%esp), %eax
> +       movl    0x4(%ebp), %edx
> +       subl    $MCOUNT_INSN_SIZE, %eax
> +
> +       call    *ftrace_trace_function
> +
> +       popl    %edx
> +       popl    %ecx
> +       popl    %eax
> +       jmp     ftrace_stub
> +END(mcount)
> +#endif /* CONFIG_DYNAMIC_FTRACE */
> +EXPORT_SYMBOL(mcount)
> +#endif /* CONFIG_FUNCTION_TRACER */
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +ENTRY(ftrace_graph_caller)
> +       pushl   %eax
> +       pushl   %ecx
> +       pushl   %edx
> +       movl    0xc(%esp), %eax
> +       lea     0x4(%ebp), %edx
> +       movl    (%ebp), %ecx
> +       subl    $MCOUNT_INSN_SIZE, %eax
> +       call    prepare_ftrace_return
> +       popl    %edx
> +       popl    %ecx
> +       popl    %eax
> +       ret
> +END(ftrace_graph_caller)
> +
> +.globl return_to_handler
> +return_to_handler:
> +       pushl   %eax
> +       pushl   %edx
> +       movl    %ebp, %eax
> +       call    ftrace_return_to_handler
> +       movl    %eax, %ecx
> +       popl    %edx
> +       popl    %eax
> +       jmp     *%ecx
> +#endif
> --
> 2.10.2
>
>