x86/ftrace: Add -mfentry support to x86_32 with DYNAMIC_FTRACE set
x86_64 has had fentry support for some time. I did not add support to x86_32 as I was unsure if it will be used much in the future. It is still very much used, and there's issues with function graph tracing with gcc playing around with the mcount frames, causing function graph to panic. The fentry code does not have this issue, and is able to cope as there is no frame to mess up. Note, this only adds support for fentry when DYNAMIC_FTRACE is set. There's really no reason to not have that set, because the performance of the machine drops significantly when it's not enabled. Keep !DYNAMIC_FTRACE around to test it off, as there's still some archs that have FTRACE but not DYNAMIC_FTRACE. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20170323143446.052202377@goodmis.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>hifive-unleashed-5.1
Steven Rostedt (VMware)
Thomas Gleixner
parent
ff04b440d2
commit
644e0e8dc7
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@ -127,7 +127,7 @@ config X86
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select HAVE_EBPF_JIT if X86_64
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select HAVE_EFFICIENT_UNALIGNED_ACCESS
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select HAVE_EXIT_THREAD
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select HAVE_FENTRY if X86_64
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select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
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select HAVE_FTRACE_MCOUNT_RECORD
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select HAVE_FUNCTION_GRAPH_TRACER
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select HAVE_FUNCTION_TRACER
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@ -9,26 +9,68 @@
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#include <asm/ftrace.h>
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#ifdef CONFIG_FUNCTION_TRACER
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#ifdef CC_USING_FENTRY
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# define function_hook __fentry__
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EXPORT_SYMBOL(__fentry__)
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#else
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# define function_hook mcount
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EXPORT_SYMBOL(mcount)
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(mcount)
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/* mcount uses a frame pointer even if CONFIG_FRAME_POINTER is not set */
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#if !defined(CC_USING_FENTRY) || defined(CONFIG_FRAME_POINTER)
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# define USING_FRAME_POINTER
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#endif
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#ifdef USING_FRAME_POINTER
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# define MCOUNT_FRAME 1 /* using frame = true */
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#else
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# define MCOUNT_FRAME 0 /* using frame = false */
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#endif
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ENTRY(function_hook)
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ret
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END(mcount)
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END(function_hook)
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ENTRY(ftrace_caller)
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#ifdef USING_FRAME_POINTER
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# ifdef CC_USING_FENTRY
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/*
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* Frame pointers are of ip followed by bp.
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* Since fentry is an immediate jump, we are left with
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* parent-ip, function-ip. We need to add a frame with
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* parent-ip followed by ebp.
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*/
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pushl 4(%esp) /* parent ip */
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pushl %ebp
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movl %esp, %ebp
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pushl 2*4(%esp) /* function ip */
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# endif
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/* For mcount, the function ip is directly above */
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pushl %ebp
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movl %esp, %ebp
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#endif
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pushl %eax
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pushl %ecx
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pushl %edx
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pushl $0 /* Pass NULL as regs pointer */
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movl 5*4(%esp), %eax
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/* Copy original ebp into %edx */
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#ifdef USING_FRAME_POINTER
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/* Load parent ebp into edx */
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movl 4*4(%esp), %edx
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#else
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/* There's no frame pointer, load the appropriate stack addr instead */
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lea 4*4(%esp), %edx
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#endif
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movl (MCOUNT_FRAME+4)*4(%esp), %eax /* load the rip */
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/* Get the parent ip */
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movl 0x4(%edx), %edx
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movl 4(%edx), %edx /* edx has ebp */
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movl function_trace_op, %ecx
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subl $MCOUNT_INSN_SIZE, %eax
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@ -40,7 +82,14 @@ ftrace_call:
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popl %edx
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popl %ecx
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popl %eax
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#ifdef USING_FRAME_POINTER
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popl %ebp
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# ifdef CC_USING_FENTRY
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addl $4,%esp /* skip function ip */
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popl %ebp /* this is the orig bp */
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addl $4, %esp /* skip parent ip */
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# endif
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#endif
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.Lftrace_ret:
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.globl ftrace_graph_call
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@ -81,6 +130,10 @@ ENTRY(ftrace_regs_caller)
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pushl %edx
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pushl %ecx
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pushl %ebx
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#ifdef CC_USING_FENTRY
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/* Load 4 off of the parent ip addr into ebp */
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lea 14*4(%esp), %ebp
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#endif
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movl 12*4(%esp), %eax /* Load ip (1st parameter) */
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subl $MCOUNT_INSN_SIZE, %eax /* Adjust ip */
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@ -119,7 +172,7 @@ GLOBAL(ftrace_regs_call)
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jmp .Lftrace_ret
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#else /* ! CONFIG_DYNAMIC_FTRACE */
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ENTRY(mcount)
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ENTRY(function_hook)
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cmpl $__PAGE_OFFSET, %esp
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jb ftrace_stub /* Paging not enabled yet? */
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@ -151,9 +204,8 @@ ftrace_stub:
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popl %ecx
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popl %eax
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jmp ftrace_stub
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END(mcount)
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END(function_hook)
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#endif /* CONFIG_DYNAMIC_FTRACE */
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EXPORT_SYMBOL(mcount)
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#endif /* CONFIG_FUNCTION_TRACER */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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@ -161,9 +213,15 @@ ENTRY(ftrace_graph_caller)
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pushl %eax
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pushl %ecx
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pushl %edx
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movl 0xc(%esp), %eax
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movl 3*4(%esp), %eax
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/* Even with frame pointers, fentry doesn't have one here */
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#ifdef CC_USING_FENTRY
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lea 4*4(%esp), %edx
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movl $0, %ecx
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#else
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lea 0x4(%ebp), %edx
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movl (%ebp), %ecx
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#endif
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subl $MCOUNT_INSN_SIZE, %eax
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call prepare_ftrace_return
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popl %edx
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@ -176,7 +234,11 @@ END(ftrace_graph_caller)
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return_to_handler:
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pushl %eax
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pushl %edx
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#ifdef CC_USING_FENTRY
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movl $0, %eax
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#else
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movl %ebp, %eax
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#endif
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call ftrace_return_to_handler
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movl %eax, %ecx
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popl %edx
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