From 41918ec82eb6f80c8b401422f27ca76c85aa0cb7 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 25 Jan 2022 15:55:24 +0100 Subject: [PATCH] ARM: ftrace: enable the graph tracer with the EABI unwinder Enable the function graph tracer in combination with the EABI unwinder, so that Thumb2 builds or Clang ARM builds can make use of it. This involves using the unwinder to locate the return address of an instrumented function on the stack, so that it can be overridden and made to refer to the ftrace handling routines that need to be called at function return. Given that for these builds, it is not guaranteed that the value of the link register is stored on the stack, fall back to the stack slot that will be used by the ftrace exit code to restore LR in the instrumented function's execution context. Signed-off-by: Ard Biesheuvel Reviewed-by: Steven Rostedt (Google) --- arch/arm/Kconfig | 2 +- arch/arm/Kconfig.debug | 2 +- arch/arm/include/asm/ftrace.h | 18 ------------------ arch/arm/kernel/Makefile | 5 +---- arch/arm/kernel/entry-ftrace.S | 28 ++++++++++++++++++++-------- arch/arm/kernel/ftrace.c | 19 +++++++++++++++++-- 6 files changed, 40 insertions(+), 34 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 70ab8d8..ec98387 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -91,7 +91,7 @@ config ARM select HAVE_EXIT_THREAD select HAVE_FAST_GUP if ARM_LPAE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL - select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG + select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !(THUMB2_KERNEL && CC_IS_CLANG) select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_GCC_PLUGINS diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 9843670..b79dc7f 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -65,7 +65,7 @@ config UNWINDER_FRAME_POINTER config UNWINDER_ARM bool "ARM EABI stack unwinder" - depends on AEABI && !FUNCTION_GRAPH_TRACER + depends on AEABI # https://github.com/ClangBuiltLinux/linux/issues/732 depends on !LD_IS_LLD || LLD_VERSION >= 110000 select ARM_UNWIND diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index b4f5fab..5358aad 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -35,26 +35,8 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) #ifndef __ASSEMBLY__ -#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) -/* - * return_address uses walk_stackframe to do it's work. If both - * CONFIG_FRAME_POINTER=y and CONFIG_ARM_UNWIND=y walk_stackframe uses unwind - * information. For this to work in the function tracer many functions would - * have to be marked with __notrace. So for now just depend on - * !CONFIG_ARM_UNWIND. - */ - void *return_address(unsigned int); -#else - -static inline void *return_address(unsigned int level) -{ - return NULL; -} - -#endif - #define ftrace_return_address(n) return_address(n) #define ARCH_HAS_SYSCALL_MATCH_SYM_NAME diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 5651185..5cebb8d 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -25,10 +25,7 @@ obj-y := elf.o entry-common.o irq.o opcodes.o \ KASAN_SANITIZE_stacktrace.o := n KASAN_SANITIZE_traps.o := n -ifneq ($(CONFIG_ARM_UNWIND),y) -obj-$(CONFIG_FRAME_POINTER) += return_address.o -endif - +obj-y += return_address.o obj-$(CONFIG_ATAGS) += atags_parse.o obj-$(CONFIG_ATAGS_PROC) += atags_proc.o obj-$(CONFIG_DEPRECATED_PARAM_STRUCT) += atags_compat.o diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index bbfa095..3e7bcac 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -100,7 +100,8 @@ ftrace_regs_call: #ifdef CONFIG_FUNCTION_GRAPH_TRACER .globl ftrace_graph_regs_call ftrace_graph_regs_call: - mov r0, r0 +ARM( mov r0, r0 ) +THUMB( nop.w ) #endif @ pop saved regs @@ -112,13 +113,18 @@ ftrace_graph_regs_call: #ifdef CONFIG_FUNCTION_GRAPH_TRACER .macro __ftrace_graph_regs_caller - sub r0, fp, #4 @ lr of instrumented routine (parent) +#ifdef CONFIG_UNWINDER_FRAME_POINTER + sub r0, fp, #4 @ lr of instrumented routine (parent) +#else + add r0, sp, #S_LR +#endif @ called from __ftrace_regs_caller - ldr r1, [sp, #S_PC] @ instrumented routine (func) + ldr r1, [sp, #S_PC] @ instrumented routine (func) mcount_adjust_addr r1, r1 - mov r2, fp @ frame pointer + mov r2, fpreg @ frame pointer + add r3, sp, #PT_REGS_SIZE bl prepare_ftrace_return @ pop registers saved in ftrace_regs_caller @@ -149,14 +155,19 @@ ftrace_call\suffix: #ifdef CONFIG_FUNCTION_GRAPH_TRACER .globl ftrace_graph_call\suffix ftrace_graph_call\suffix: - mov r0, r0 +ARM( mov r0, r0 ) +THUMB( nop.w ) #endif mcount_exit .endm .macro __ftrace_graph_caller +#ifdef CONFIG_UNWINDER_FRAME_POINTER sub r0, fp, #4 @ &lr of instrumented routine (&parent) +#else + add r0, sp, #20 +#endif #ifdef CONFIG_DYNAMIC_FTRACE @ called from __ftrace_caller, saved in mcount_enter ldr r1, [sp, #16] @ instrumented routine (func) @@ -165,7 +176,8 @@ ftrace_graph_call\suffix: @ called from __mcount, untouched in lr mcount_adjust_addr r1, lr @ instrumented routine (func) #endif - mov r2, fp @ frame pointer + mov r2, fpreg @ frame pointer + add r3, sp, #24 bl prepare_ftrace_return mcount_exit .endm @@ -244,14 +256,14 @@ ENDPROC(ftrace_graph_regs_caller) .purgem mcount_exit #ifdef CONFIG_FUNCTION_GRAPH_TRACER - .globl return_to_handler -return_to_handler: +ENTRY(return_to_handler) stmdb sp!, {r0-r3} add r0, sp, #16 @ sp at exit of instrumented routine bl ftrace_return_to_handler mov lr, r0 @ r0 has real ret addr ldmia sp!, {r0-r3} ret lr +ENDPROC(return_to_handler) #endif ENTRY(ftrace_stub) diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index ea23969..83cc068 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -22,6 +22,7 @@ #include #include #include +#include #include /* @@ -224,8 +225,10 @@ int ftrace_make_nop(struct module *mod, #endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER +asmlinkage void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, - unsigned long frame_pointer) + unsigned long frame_pointer, + unsigned long stack_pointer) { unsigned long return_hooker = (unsigned long) &return_to_handler; unsigned long old; @@ -236,6 +239,18 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) { /* FP points one word below parent's top of stack */ frame_pointer += 4; + } else { + struct stackframe frame = { + .fp = frame_pointer, + .sp = stack_pointer, + .lr = self_addr, + .pc = self_addr, + }; + if (unwind_frame(&frame) < 0) + return; + if (frame.lr != self_addr) + parent = frame.lr_addr; + frame_pointer = frame.sp; } old = *parent; @@ -258,7 +273,7 @@ static int __ftrace_modify_caller(unsigned long *callsite, unsigned long caller_fn = (unsigned long) func; unsigned long pc = (unsigned long) callsite; unsigned long branch = arm_gen_branch(pc, caller_fn); - unsigned long nop = 0xe1a00000; /* mov r0, r0 */ + unsigned long nop = arm_gen_nop(); unsigned long old = enable ? nop : branch; unsigned long new = enable ? branch : nop; -- 2.7.4