Messages in this thread Patch in this message | | | From | Jean-Jacques Hiblot <> | Date | Wed, 25 Jan 2017 19:30:32 +0100 | Subject | Re: [PATCHv2] arm: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS |
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Abel, I tested it partially. It's seems OK if I have FRAME_POINTER enabled and it breaks otherwise.
My test case attaches a tracing handler to a function "myfunc":
static struct ftrace_ops kprobe_ftrace_ops __read_mostly = { .func = jjh_ftrace_handler, .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_DYNAMIC, };
ftrace_set_filter(&kprobe_ftrace_ops, "myfunc", 4, 0); register_ftrace_function(&kprobe_ftrace_ops);
I won't send the actual code because it's too messy. If you need help to reproduce, I'll try to extract the relevant part.
Before the crash I observe the following warning. ------------[ cut here ]------------ WARNING: CPU: 0 PID: 9 at kernel/trace/ftrace.c:2526 ftrace_modify_all_code+0xd8/0x158 Modules linked in: jjh_test(+) CPU: 0 PID: 9 Comm: migration/0 Tainted: G W 4.7.0+ #53 Hardware name: ARM-Versatile Express [<8010f7bc>] (unwind_backtrace) from [<8010b6f8>] (show_stack+0x18/0x1c) [<8010b6f8>] (show_stack) from [<803a1548>] (dump_stack+0x80/0xa0) [<803a1548>] (dump_stack) from [<8011ef20>] (__warn+0xe0/0x10c) [<8011ef20>] (__warn) from [<8011ef74>] (warn_slowpath_null+0x28/0x30) [<8011ef74>] (warn_slowpath_null) from [<8019d2a4>] (ftrace_modify_all_code+0xd8/0x158) [<8019d2a4>] (ftrace_modify_all_code) from [<8019d330>] (__ftrace_modify_code+0xc/0x14) [<8019d330>] (__ftrace_modify_code) from [<80198908>] (multi_cpu_stop+0xe8/0x114) [<80198908>] (multi_cpu_stop) from [<80198588>] (cpu_stopper_thread+0x60/0x134) [<80198588>] (cpu_stopper_thread) from [<8013f428>] (smpboot_thread_fn+0x148/0x1c4) [<8013f428>] (smpboot_thread_fn) from [<8013c00c>] (kthread+0xe0/0xfc) [<8013c00c>] (kthread) from [<80107db8>] (ret_from_fork+0x14/0x3c) ---[ end trace f7d50cc2a4627fb1 ]---
Jean-Jacques
2017-01-25 0:24 GMT+01:00 Abel Vesa <abelvesa@linux.com>: > The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a ftrace > operation to specify if registers need to saved/restored by the ftrace handler. > This is needed by kgraft and possibly other ftrace-based tools, and the ARM > architecture is currently lacking this feature. It would also be the first step > to support the "Kprobes-on-ftrace" optimization on ARM. > > This patch introduces a new ftrace handler that stores the registers on the > stack before calling the next stage. The registers are restored from the stack > before going back to the instrumented function. > > A side-effect of this patch is to activate the support for ftrace_modify_call() > as it defines ARCH_SUPPORTS_FTRACE_OPS for the ARM architecture. > > Signed-off-by: Abel Vesa <abelvesa@linux.com> > --- > arch/arm/Kconfig | 1 + > arch/arm/include/asm/ftrace.h | 4 +++ > arch/arm/kernel/entry-ftrace.S | 79 ++++++++++++++++++++++++++++++++++++++++++ > arch/arm/kernel/ftrace.c | 33 ++++++++++++++++++ > 4 files changed, 117 insertions(+) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 186c4c2..db40973 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -50,6 +50,7 @@ config ARM > select HAVE_DMA_API_DEBUG > select HAVE_DMA_CONTIGUOUS if MMU > select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU > + select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE > select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU > select HAVE_EXIT_THREAD > select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) > diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h > index 22b7311..f379881 100644 > --- a/arch/arm/include/asm/ftrace.h > +++ b/arch/arm/include/asm/ftrace.h > @@ -1,6 +1,10 @@ > #ifndef _ASM_ARM_FTRACE > #define _ASM_ARM_FTRACE > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +#define ARCH_SUPPORTS_FTRACE_OPS 1 > +#endif > + > #ifdef CONFIG_FUNCTION_TRACER > #define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc)) > #define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S > index c73c403..fcdcc3a 100644 > --- a/arch/arm/kernel/entry-ftrace.S > +++ b/arch/arm/kernel/entry-ftrace.S > @@ -92,12 +92,74 @@ > 2: mcount_exit > .endm > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + > +.macro __ftrace_regs_caller > + > + add ip, sp, #4 @ move in IP the value of SP as it was > + @ before the push {lr} of the mcount mechanism > + stmdb sp!, {ip,lr,pc} > + stmdb sp!, {r0-r11,lr} > + > + @ stack content at this point: > + @ 0 4 44 48 52 56 60 64 > + @ RO | R1 | ... | R11 | LR | SP + 4 | LR | PC | previous LR | > + > + mov r3, sp @ struct pt_regs* > + ldr r2, =function_trace_op > + ldr r2, [r2] @ pointer to the current > + @ function tracing op > + ldr r1, [sp, #64] @ lr of instrumented func > + mcount_adjust_addr r0, lr @ instrumented function > + > + .globl ftrace_regs_call > +ftrace_regs_call: > + bl ftrace_stub > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + .globl ftrace_graph_regs_call > +ftrace_graph_regs_call: > + mov r0, r0 > +#endif > + ldr lr, [sp, #64] @ get the previous LR value from stack > + ldmia sp, {r0-r11, ip, sp} @ pop the saved registers INCLUDING > + @ the stack pointer > + ret ip > +.endm > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +.macro __ftrace_graph_regs_caller > + > + sub r0, fp, #4 @ lr of instrumented routine (parent) > + > + @ called from __ftrace_regs_caller > + ldr r1, [sp, #56] @ instrumented routine (func) > + mcount_adjust_addr r1, r1 > + > + sub r2, r0, #4 @ frame pointer > + bl prepare_ftrace_return > + > + ldr lr, [sp, #64] @ restore lr from the stack > + ldmia sp, {r0-r11, ip, sp} @ restore r0 through sp > + ret ip > + > +.endm > +#endif > +#endif > + > .macro __ftrace_caller suffix > mcount_enter > > mcount_get_lr r1 @ lr of instrumented func > mcount_adjust_addr r0, lr @ instrumented function > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + ldr r2, =function_trace_op > + ldr r2, [r2] @ pointer to the current > + @ function tracing op > + mov r3, #0 @ regs is NULL > +#endif > + > .globl ftrace_call\suffix > ftrace_call\suffix: > bl ftrace_stub > @@ -212,6 +274,15 @@ UNWIND(.fnstart) > __ftrace_caller > UNWIND(.fnend) > ENDPROC(ftrace_caller) > + > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +ENTRY(ftrace_regs_caller) > +UNWIND(.fnstart) > + __ftrace_regs_caller > +UNWIND(.fnend) > +ENDPROC(ftrace_regs_caller) > +#endif > + > #endif > > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > @@ -220,6 +291,14 @@ UNWIND(.fnstart) > __ftrace_graph_caller > UNWIND(.fnend) > ENDPROC(ftrace_graph_caller) > + > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +ENTRY(ftrace_graph_regs_caller) > +UNWIND(.fnstart) > + __ftrace_graph_regs_caller > +UNWIND(.fnend) > +ENDPROC(ftrace_graph_regs_caller) > +#endif > #endif > > .purgem mcount_enter > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c > index 3f17594..d8d4753 100644 > --- a/arch/arm/kernel/ftrace.c > +++ b/arch/arm/kernel/ftrace.c > @@ -139,6 +139,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) > > ret = ftrace_modify_code(pc, 0, new, false); > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + if (!ret) { > + pc = (unsigned long)&ftrace_regs_call; > + new = ftrace_call_replace(pc, (unsigned long)func); > + > + ret = ftrace_modify_code(pc, 0, new, false); > + } > +#endif > + > #ifdef CONFIG_OLD_MCOUNT > if (!ret) { > pc = (unsigned long)&ftrace_call_old; > @@ -157,6 +166,20 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) > unsigned long ip = rec->ip; > > old = ftrace_nop_replace(rec); > + > + new = ftrace_call_replace(ip, adjust_address(rec, addr)); > + > + return ftrace_modify_code(rec->ip, old, new, true); > +} > + > +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, > + unsigned long addr) > +{ > + unsigned long new, old; > + unsigned long ip = rec->ip; > + > + old = ftrace_call_replace(ip, adjust_address(rec, old_addr)); > + > new = ftrace_call_replace(ip, adjust_address(rec, addr)); > > return ftrace_modify_code(rec->ip, old, new, true); > @@ -229,6 +252,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, > extern unsigned long ftrace_graph_call; > extern unsigned long ftrace_graph_call_old; > extern void ftrace_graph_caller_old(void); > +extern unsigned long ftrace_graph_regs_call; > +extern void ftrace_graph_regs_caller(void); > > static int __ftrace_modify_caller(unsigned long *callsite, > void (*func) (void), bool enable) > @@ -251,6 +276,14 @@ static int ftrace_modify_graph_caller(bool enable) > ftrace_graph_caller, > enable); > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + if (!ret) > + ret = __ftrace_modify_caller(&ftrace_graph_regs_call, > + ftrace_graph_regs_caller, > + enable); > +#endif > + > + > #ifdef CONFIG_OLD_MCOUNT > if (!ret) > ret = __ftrace_modify_caller(&ftrace_graph_call_old, > -- > 2.7.4 >
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