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: Jean-Jacques Hiblot <[email protected]> --- arch/arm/Kconfig | 2 ++ arch/arm/include/asm/ftrace.h | 3 ++ arch/arm/kernel/entry-common.S | 68 +++++++++++++++++++++++++++++++++++++++++- arch/arm/kernel/ftrace.c | 34 +++++++++++++++++++++ 4 files changed, 106 insertions(+), 1 deletion(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 32cbbd5..6f928ee 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -39,6 +39,7 @@ config ARM select HAVE_DMA_ATTRS select HAVE_DMA_CONTIGUOUS if MMU select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) + 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_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL) @@ -72,6 +73,7 @@ config ARM select PERF_USE_VMALLOC select RTC_LIB select SYS_SUPPORTS_APM_EMULATION + select FRAME_POINTER if DYNAMIC_FTRACE_WITH_REGS && FUNCTION_GRAPH_TRACER # Above selects are sorted alphabetically; please add new ones # according to that. Thanks. help diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index 39eb16b..d8e9bea 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -10,6 +10,9 @@ extern void mcount(void); extern void __gnu_mcount_nc(void); #ifdef CONFIG_DYNAMIC_FTRACE + +#define ARCH_SUPPORTS_FTRACE_OPS 1 + struct dyn_arch_ftrace { #ifdef CONFIG_OLD_MCOUNT bool old_mcount; diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index e52fe5a..9594fe2 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -197,7 +197,10 @@ ENDPROC(ret_from_fork) mcount_get_lr r1 @ lr of instrumented func mcount_adjust_addr r0, lr @ instrumented function - + ldr r2, =function_trace_op + ldr r2, [r2] @ pointer to the current + @ function tracing op + mov r3, #0 @ regs is NULL .globl ftrace_call\suffix ftrace_call\suffix: bl ftrace_stub @@ -211,6 +214,38 @@ ftrace_graph_call\suffix: mcount_exit .endm +.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 + .macro __ftrace_graph_caller sub r0, fp, #4 @ &lr of instrumented routine (&parent) #ifdef CONFIG_DYNAMIC_FTRACE @@ -226,6 +261,24 @@ ftrace_graph_call\suffix: mcount_exit .endm + +.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 + + mov r2, fp @ frame pointer + bl prepare_ftrace_return + + ldr lr, [fp, #-4] @ restore LR from the stack + ldmia sp, {r0-r11, ip, sp} @ pop the saved registers INCLUDING + @ the stack pointer + ret ip +.endm + #ifdef CONFIG_OLD_MCOUNT /* * mcount @@ -312,14 +365,27 @@ UNWIND(.fnstart) __ftrace_caller UNWIND(.fnend) ENDPROC(ftrace_caller) + +ENTRY(ftrace_regs_caller) +UNWIND(.fnstart) + __ftrace_regs_caller +UNWIND(.fnend) +ENDPROC(ftrace_regs_caller) #endif + #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(ftrace_graph_caller) UNWIND(.fnstart) __ftrace_graph_caller UNWIND(.fnend) ENDPROC(ftrace_graph_caller) + +ENTRY(ftrace_graph_regs_caller) +UNWIND(.fnstart) + __ftrace_graph_regs_caller +UNWIND(.fnend) +ENDPROC(ftrace_graph_regs_caller) #endif .purgem mcount_enter diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index af9a8a9..35c5743 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -130,6 +130,16 @@ int ftrace_update_ftrace_func(ftrace_func_t func) } #endif + +#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 + return ret; } @@ -139,6 +149,20 @@ 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); @@ -211,6 +235,9 @@ 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) @@ -240,6 +267,13 @@ static int ftrace_modify_graph_caller(bool enable) enable); #endif +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + if (!ret) + ret = __ftrace_modify_caller(&ftrace_graph_regs_call, + ftrace_graph_regs_caller, + enable); +#endif + return ret; } -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
