Messages in this thread Patch in this message | | | Date | Thu, 23 Apr 2009 11:35:42 -0700 | From | Tim Bird <> | Subject | [PATCH] Add function graph tracer support for ARM (resend) |
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My first post of this wasn't wide enough. Now adding the linux-arm-kernel list and a few more CC:s. Sorry if you get this twice.
Add ftrace function-graph tracer support for ARM.
This includes adding code in mcount to check for (and call) a registered function graph trace entry routine, and adding infrastructure to the threadinfo structure to support a return trampoline.
I wrote a separate program to scan the kernel assembly output and validate that callframes for mcount are generated properly. (It's available upon request for anyone interested.)
Much of the code in arch/arm/kernel/ftrace.c was cloned from arch/x86/kernel/ftrace.c
IRQENTRY_TEXT was added to vmlinux.lds.S (to eliminate a compiler error on kernel/trace/trace_functions_graph.c), although no routines were marked as __irq_entry.
FIXTHIS indicates questions or areas of uncertainty.
This works for me with a gcc 4.1.1 compiler (EABI with frame pointers turned on) on an OMAP OSK board, with kernel 2.6.29.
The use of "already_here" works around trace entry nesting (I believe due to instrumentation of either cpu_clock or raw_smp_processor_id). Advice on the best way to deal with this would be appreciated. (that is, whether to use the guard variable, or just un-instrument the offending routines).
Thanks for any feedback.
Signed-off-by: <tim.bird@am.sony.com> --- arch/arm/Kconfig | 1 arch/arm/include/asm/ftrace.h | 28 +++++++ arch/arm/kernel/Makefile | 3 arch/arm/kernel/entry-common.S | 29 +++++++- arch/arm/kernel/ftrace.c | 146 +++++++++++++++++++++++++++++++++++++++++ arch/arm/kernel/vmlinux.lds.S | 1 6 files changed, 204 insertions(+), 4 deletions(-)
--- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -17,6 +17,7 @@ config ARM select HAVE_KPROBES if (!XIP_KERNEL) select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_FUNCTION_TRACER if (!XIP_KERNEL) + select HAVE_FUNCTION_GRAPH_TRACER if (!XIP_KERNEL) select HAVE_GENERIC_DMA_COHERENT help The ARM series is a line of low-power-consumption RISC chip designs --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -7,8 +7,32 @@
#ifndef __ASSEMBLY__ extern void mcount(void); -#endif +#endif /* __ASSEMBLY__ */
-#endif +#endif /* CONFIG_FUNCTION_TRACER */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +#ifndef __ASSEMBLY__ + +/* + * Stack of return addresses for functions of a thread. + * Used in struct thread_info + */ +struct ftrace_ret_stack { + unsigned long ret; + unsigned long func; + unsigned long long calltime; +}; + +/* + * Primary handler of a function return. + * It relays on ftrace_return_to_handler. + * Defined in entry-common.S + */ +extern void return_to_handler(void); + +#endif /* __ASSEMBLY__ */ +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#endif /* _ASM_ARM_FTRACE */ --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -4,7 +4,7 @@
AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
-ifdef CONFIG_DYNAMIC_FTRACE +ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_ftrace.o = -pg endif
@@ -23,6 +23,7 @@ obj-$(CONFIG_ISA_DMA) += dma-isa.o obj-$(CONFIG_PCI) += bios32.o isa.o obj-$(CONFIG_SMP) += smp.o obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o +obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o obj-$(CONFIG_KPROBES) += kprobes.o kprobes-decode.o obj-$(CONFIG_ATAGS_PROC) += atags.o --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -135,8 +135,16 @@ ENTRY(mcount) adr r0, ftrace_stub cmp r0, r2 bne trace + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + ldr r1, =ftrace_graph_return + ldr r2, [r1] + cmp r0, r2 @ if *ftrace_graph_return != ftrace_stub + bne ftrace_graph_caller +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ + ldr lr, [fp, #-4] @ restore lr - ldmia sp!, {r0-r3, pc} + ldmia sp!, {r0-r3, pc} @ return doing nothing
trace: ldr r1, [fp, #-4] @ lr of instrumented routine @@ -147,6 +155,25 @@ trace: mov lr, r1 @ restore lr ldmia sp!, {r0-r3, pc}
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER +ENTRY(ftrace_graph_caller) + sub r0, fp, #4 @ &lr of instrumented routine (&parent) + mov r1, lr @ instrumented routine (func) + sub r1, r1, #MCOUNT_INSN_SIZE + bl prepare_ftrace_return + ldr lr, [fp, #-4] @ restore lr + ldmia sp!, {r0-r3, pc} + + .globl return_to_handler +return_to_handler: + stmdb sp!, {r0-r3} + bl ftrace_return_to_handler + mov lr, r0 @ r0 has real ret addr + ldmia sp!, {r0-r3} + mov pc, lr + +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ + #endif /* CONFIG_DYNAMIC_FTRACE */
.globl ftrace_stub --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -16,6 +16,8 @@ #include <asm/cacheflush.h> #include <asm/ftrace.h>
+#ifdef CONFIG_DYNAMIC_FTRACE + #define PC_OFFSET 8 #define BL_OPCODE 0xeb000000 #define BL_OFFSET_MASK 0x00ffffff @@ -101,3 +103,147 @@ int __init ftrace_dyn_arch_init(void *da ftrace_mcount_set(data); return 0; } + +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +/* Add a function return address to the trace stack on thread info.*/ +static int push_return_trace(unsigned long ret, unsigned long long time, + unsigned long func, int *depth) +{ + int index; + + if (!current->ret_stack) + return -EBUSY; + + /* The return trace stack is full */ + if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) { + atomic_inc(¤t->trace_overrun); + return -EBUSY; + } + + index = ++current->curr_ret_stack; + barrier(); + current->ret_stack[index].ret = ret; + current->ret_stack[index].func = func; + current->ret_stack[index].calltime = time; + *depth = index; + + return 0; +} + +/* + * Retrieve a function return address from the trace stack on thread info. + * set the address to return to in *ret + */ +static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret) +{ + int index; + + index = current->curr_ret_stack; + + if (unlikely(index < 0)) { + ftrace_graph_stop(); + WARN_ON(1); + /* Might as well panic, otherwise we have no where to go */ + *ret = (unsigned long)panic; + return; + } + + *ret = current->ret_stack[index].ret; + trace->func = current->ret_stack[index].func; + trace->calltime = current->ret_stack[index].calltime; + trace->overrun = atomic_read(¤t->trace_overrun); + trace->depth = index; + barrier(); + current->curr_ret_stack--; +} + +int already_here; /* starts at 0 */ + +/* + * Send the trace to the ring-buffer + * @return the original return address + */ +unsigned long ftrace_return_to_handler(void) +{ + struct ftrace_graph_ret trace; + unsigned long ret; + + /* guard against trace entry while handling a trace exit */ + already_here++; + + pop_return_trace(&trace, &ret); + trace.rettime = cpu_clock(raw_smp_processor_id()); + ftrace_graph_return(&trace); + + if (unlikely(!ret)) { + ftrace_graph_stop(); + WARN_ON(1); + /* Might as well panic. Where else to go? */ + ret = (unsigned long)panic; + } + + already_here--; + return ret; +} + +/* + * Hook the return address and push it in the stack of return addrs + * in current thread info. + */ + +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) +{ + unsigned long old; + unsigned long long calltime; + + struct ftrace_graph_ent trace; + unsigned long return_hooker = (unsigned long) + &return_to_handler; + + if (already_here) + return; + already_here++; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) { + already_here--; + return; + } + + /* FIXTHIS - need a local_irqsave here?, (to fend off ints?) */ + + /* FIXTHIS - x86 protects against a fault during this operation!*/ + old = *parent; + *parent = return_hooker; + + if (unlikely(!__kernel_text_address(old))) { + ftrace_graph_stop(); + *parent = old; + WARN_ON(1); + already_here--; + return; + } + + /* FIXTHIS - trace entry appears to nest inside following */ + calltime = cpu_clock(raw_smp_processor_id()); + + if (push_return_trace(old, calltime, + self_addr, &trace.depth) == -EBUSY) { + *parent = old; + already_here--; + return; + } + + trace.func = self_addr; + + /* Only trace if the calling function expects to */ + if (!ftrace_graph_entry(&trace)) { + current->curr_ret_stack--; + *parent = old; + } + + already_here--; +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -95,6 +95,7 @@ SECTIONS SCHED_TEXT LOCK_TEXT KPROBES_TEXT + IRQENTRY_TEXT #ifdef CONFIG_MMU *(.fixup) #endif
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