ftrace/x86: Ftrace cleanup and add support for -mfentry on x86_32
Subsystems (3)
Steven Rostedt
maintainer[
Ingo, Thomas or H.Peter,
I believe this is all set to go now. I updated those patches that Linus commented on and I don't believe there are any more issues. I ran this through several tests (although some of my tests are failing due to bugs introduced by others in 4.11-rc2). You can take this as a patch series, or you can pull from my tree defined below. It's based on 4.11-rc2 as I noticed that tip/x86/core is rather outdated, and Linus is fine with basing off of his tagged releases.
]
With the issues of gcc screwing around with the mcount stack frame causing function graph tracer to panic on x86_32, and with Linus saying that we should start deprecating mcount (at least on x86), I figured that x86_32 needs to support fentry.
First, I renamed mcount_64.S to ftrace_64.S. As we want to get away from mcount, having the ftrace code in a file called mcount seems rather backwards.
Next I moved the ftrace code out of entry_32.S. It's not in entry_64.S and it does not belong in entry_32.S.
I noticed that the x86_32 code has the same issue as the x86_64 did in the past with respect to a stack frame. I fixed that just for the main ftrace_caller. The ftrace_regs_caller is rather special, and so is function graph tracing.
I realized the ftrace_regs_caller code was complex due to me aggressively saving flags, even though I could still do push, lea and mov without changing them. That made the logic a little nicer.
Finally I added the fentry code.
I tested this with an older compiler (for mcount) with and without FRAME_POINTER set. I also did it with a new compiler (with fentry), with and without FRAME_POINTER. I tested function tracing, stack tracing, function_graph tracing, and kprobes (as that uses the ftrace_regs_caller).
Please pull (or take the patch series) from:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
tip/x86/ftrace
Head SHA1: 71a281dd0356fb7cb207e3387c2716b887b646de
[ Note, all is the same from v5 but patch 2, so I'm only posting that one ]
Steven Rostedt (VMware) (6):
ftrace/x86_64: Rename mcount_64.S to ftrace_64.S ftrace/x86_32: Move the ftrace specific code out of entry_32.S ftrace/x86_32: Add stack frame pointer to ftrace_caller ftrace/x86_32: Clean up ftrace_regs_caller
ftrace/x86_32: Add -mfentry support to x86_32 with DYNAMIC_FTRACE set ftrace/x86: Use Makefile logic instead of #ifdef for compiling ftrace_*.o
----
Changes from v5:
Removed file name from header comment. (Thomas Gleixner)
arch/x86/Kconfig | 2 +-
arch/x86/entry/entry_32.S | 169 -------------------
arch/x86/kernel/Makefile | 5 +-
arch/x86/kernel/ftrace_32.S | 244 +++++++++++++++++++++++++++
arch/x86/kernel/{mcount_64.S => ftrace_64.S} | 6 -
5 files changed, 248 insertions(+), 178 deletions(-)
create mode 100644 arch/x86/kernel/ftrace_32.S
rename arch/x86/kernel/{mcount_64.S => ftrace_64.S} (98%)Diff against v5:
arch/x86/kernel/ftrace_32.S +0 -2
@@ -1,6 +1,4 @@ /* - * linux/arch/x86_64/ftrace_32.S - * * Copyright (C) 2017 Steven Rostedt, VMware Inc. */
arch/x86/kernel/ftrace_64.S +0 -2
@@ -1,6 +1,4 @@ /* - * linux/arch/x86_64/ftrace_64.S - * * Copyright (C) 2014 Steven Rostedt, Red Hat Inc */
Steven Rostedt
maintainerPATCH v6 1/1 ftrace/x86_32: Move the ftrace specific code out of entry_32.S
From: "Steven Rostedt (VMware)" <[email protected]>
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.
Also removed the file name from the comment header in ftrace_64.S.
--- arch/x86/entry/entry_32.S | 169 ------------------------------------------ arch/x86/kernel/Makefile | 1 + arch/x86/kernel/ftrace_32.S | 175 ++++++++++++++++++++++++++++++++++++++++++++ arch/x86/kernel/ftrace_64.S | 2 - 4 files changed, 176 insertions(+), 171 deletions(-) create mode 100644 arch/x86/kernel/ftrace_32.S
arch/x86/entry/entry_32.S +0 -169
@@ -35,16 +35,13 @@ #include <asm/errno.h> #include <asm/segment.h> #include <asm/smp.h> -#include <asm/page_types.h> #include <asm/percpu.h> #include <asm/processor-flags.h> -#include <asm/ftrace.h> #include <asm/irq_vectors.h> #include <asm/cpufeatures.h> #include <asm/alternative-asm.h> #include <asm/asm.h> #include <asm/smap.h> -#include <asm/export.h> #include <asm/frame.h> .section .entry.text, "ax"
@@ -886,172 +883,6 @@ BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR, #endif /* CONFIG_HYPERV */ -#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 $MCOUNT_INSN_SIZE, %eax - call prepare_ftrace_return - popl %edx - popl %ecx - popl %eax - ret -END(ftrace_graph_caller) - -.globl return_to_handler -return_to_handler: - pushl %eax - pushl %edx - movl %ebp, %eax - call ftrace_return_to_handler - movl %eax, %ecx - popl %edx - popl %eax - jmp *%ecx -#endif - #ifdef CONFIG_TRACING ENTRY(trace_page_fault) ASM_CLAC
arch/x86/kernel/Makefile +1 -0
@@ -47,6 +47,7 @@ obj-y += setup.o x86_init.o i8259.o irqinit.o jump_label.o obj-$(CONFIG_IRQ_WORK) += irq_work.o obj-y += probe_roms.o obj-$(CONFIG_X86_64) += sys_x86_64.o ftrace_64.o +obj-$(CONFIG_X86_32) += ftrace_32.o obj-$(CONFIG_X86_ESPFIX64) += espfix_64.o obj-$(CONFIG_SYSFS) += ksysfs.o obj-y += bootflag.o e820.o
arch/x86/kernel/ftrace_32.S new file +175 -0
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arch/x86/kernel/ftrace_64.S +0 -2
@@ -1,6 +1,4 @@ /* - * linux/arch/x86_64/mcount_64.S - * * Copyright (C) 2014 Steven Rostedt, Red Hat Inc */
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