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Date: Wed, 22 Mar 2017 23:29:25 +0900
From: Namhyung Kim <namhyung@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...capital.net>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 2/6] ftrace/x86_32: Move the ftrace specific code out of entry_32.S
Hi Steve,
On Wed, Mar 22, 2017 at 10:35 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
>
> 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@...dmis.org>
> ---
[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, ®s->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
>
>
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