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ARM: 8678/1: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS
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> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Abel Vesa
Russell King
parent
1515b186c2
commit
620176f335
@ -56,6 +56,7 @@ config ARM
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select HAVE_DMA_API_DEBUG
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select HAVE_DMA_CONTIGUOUS if MMU
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select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU
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select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
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select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
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select HAVE_EXIT_THREAD
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select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)
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@ -1,6 +1,10 @@
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#ifndef _ASM_ARM_FTRACE
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#define _ASM_ARM_FTRACE
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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#define ARCH_SUPPORTS_FTRACE_OPS 1
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#endif
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#ifdef CONFIG_FUNCTION_TRACER
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#define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc))
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#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
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@ -92,12 +92,95 @@
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2: mcount_exit
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.endm
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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.macro __ftrace_regs_caller
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sub sp, sp, #8 @ space for PC and CPSR OLD_R0,
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@ OLD_R0 will overwrite previous LR
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add ip, sp, #12 @ move in IP the value of SP as it was
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@ before the push {lr} of the mcount mechanism
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str lr, [sp, #0] @ store LR instead of PC
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ldr lr, [sp, #8] @ get previous LR
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str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR
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stmdb sp!, {ip, lr}
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stmdb sp!, {r0-r11, lr}
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@ stack content at this point:
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@ 0 4 48 52 56 60 64 68 72
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@ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 |
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mov r3, sp @ struct pt_regs*
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ldr r2, =function_trace_op
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ldr r2, [r2] @ pointer to the current
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@ function tracing op
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ldr r1, [sp, #S_LR] @ lr of instrumented func
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ldr lr, [sp, #S_PC] @ get LR
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mcount_adjust_addr r0, lr @ instrumented function
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.globl ftrace_regs_call
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ftrace_regs_call:
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bl ftrace_stub
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.globl ftrace_graph_regs_call
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ftrace_graph_regs_call:
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mov r0, r0
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#endif
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@ pop saved regs
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ldmia sp!, {r0-r12} @ restore r0 through r12
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ldr ip, [sp, #8] @ restore PC
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ldr lr, [sp, #4] @ restore LR
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ldr sp, [sp, #0] @ restore SP
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mov pc, ip @ return
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.endm
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.macro __ftrace_graph_regs_caller
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sub r0, fp, #4 @ lr of instrumented routine (parent)
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@ called from __ftrace_regs_caller
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ldr r1, [sp, #S_PC] @ instrumented routine (func)
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mcount_adjust_addr r1, r1
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mov r2, fp @ frame pointer
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bl prepare_ftrace_return
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@ pop registers saved in ftrace_regs_caller
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ldmia sp!, {r0-r12} @ restore r0 through r12
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ldr ip, [sp, #8] @ restore PC
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ldr lr, [sp, #4] @ restore LR
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ldr sp, [sp, #0] @ restore SP
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mov pc, ip @ return
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.endm
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#endif
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#endif
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.macro __ftrace_caller suffix
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mcount_enter
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mcount_get_lr r1 @ lr of instrumented func
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mcount_adjust_addr r0, lr @ instrumented function
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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ldr r2, =function_trace_op
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ldr r2, [r2] @ pointer to the current
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@ function tracing op
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mov r3, #0 @ regs is NULL
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#endif
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.globl ftrace_call\suffix
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ftrace_call\suffix:
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bl ftrace_stub
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@ -212,6 +295,15 @@ UNWIND(.fnstart)
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__ftrace_caller
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UNWIND(.fnend)
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ENDPROC(ftrace_caller)
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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ENTRY(ftrace_regs_caller)
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UNWIND(.fnstart)
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__ftrace_regs_caller
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UNWIND(.fnend)
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ENDPROC(ftrace_regs_caller)
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#endif
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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@ -220,6 +312,14 @@ UNWIND(.fnstart)
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__ftrace_graph_caller
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UNWIND(.fnend)
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ENDPROC(ftrace_graph_caller)
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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ENTRY(ftrace_graph_regs_caller)
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UNWIND(.fnstart)
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__ftrace_graph_regs_caller
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UNWIND(.fnend)
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ENDPROC(ftrace_graph_regs_caller)
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#endif
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#endif
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.purgem mcount_enter
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@ -141,6 +141,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
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ret = ftrace_modify_code(pc, 0, new, false);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret) {
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pc = (unsigned long)&ftrace_regs_call;
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new = ftrace_call_replace(pc, (unsigned long)func);
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ret = ftrace_modify_code(pc, 0, new, false);
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}
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#endif
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#ifdef CONFIG_OLD_MCOUNT
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if (!ret) {
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pc = (unsigned long)&ftrace_call_old;
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@ -159,11 +168,29 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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unsigned long ip = rec->ip;
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old = ftrace_nop_replace(rec);
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new = ftrace_call_replace(ip, adjust_address(rec, addr));
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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unsigned long addr)
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{
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unsigned long new, old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
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new = ftrace_call_replace(ip, adjust_address(rec, addr));
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#endif
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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@ -231,6 +258,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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extern unsigned long ftrace_graph_call;
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extern unsigned long ftrace_graph_call_old;
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extern void ftrace_graph_caller_old(void);
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extern unsigned long ftrace_graph_regs_call;
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extern void ftrace_graph_regs_caller(void);
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static int __ftrace_modify_caller(unsigned long *callsite,
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void (*func) (void), bool enable)
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@ -253,6 +282,14 @@ static int ftrace_modify_graph_caller(bool enable)
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ftrace_graph_caller,
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enable);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret)
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ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
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ftrace_graph_regs_caller,
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enable);
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#endif
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#ifdef CONFIG_OLD_MCOUNT
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if (!ret)
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ret = __ftrace_modify_caller(&ftrace_graph_call_old,
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