/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <asm/assembler.h>
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#include <asm/ftrace.h>
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#include <asm/unwind.h>
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#include "entry-header.S"
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/*
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* When compiling with -pg, gcc inserts a call to the mcount routine at the
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* start of every function. In mcount, apart from the function's address (in
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* lr), we need to get hold of the function's caller's address.
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*
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* Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
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*
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* bl mcount
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*
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* These versions have the limitation that in order for the mcount routine to
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* be able to determine the function's caller's address, an APCS-style frame
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* pointer (which is set up with something like the code below) is required.
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*
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* mov ip, sp
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* push {fp, ip, lr, pc}
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* sub fp, ip, #4
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*
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* With EABI, these frame pointers are not available unless -mapcs-frame is
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* specified, and if building as Thumb-2, not even then.
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*
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* Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
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* with call sites like:
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*
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* push {lr}
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* bl __gnu_mcount_nc
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*
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* With these compilers, frame pointers are not necessary.
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*
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* mcount can be thought of as a function called in the middle of a subroutine
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* call. As such, it needs to be transparent for both the caller and the
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* callee: the original lr needs to be restored when leaving mcount, and no
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* registers should be clobbered. (In the __gnu_mcount_nc implementation, we
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* clobber the ip register. This is OK because the ARM calling convention
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* allows it to be clobbered in subroutines and doesn't use it to hold
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* parameters.)
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*
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* When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
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* for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
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* arch/arm/kernel/ftrace.c).
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*/
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#ifndef CONFIG_OLD_MCOUNT
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#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
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#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
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#endif
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#endif
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.macro mcount_adjust_addr rd, rn
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bic \rd, \rn, #1 @ clear the Thumb bit if present
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sub \rd, \rd, #MCOUNT_INSN_SIZE
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.endm
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.macro __mcount suffix
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mcount_enter
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ldr r0, =ftrace_trace_function
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ldr r2, [r0]
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adr r0, .Lftrace_stub
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cmp r0, r2
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bne 1f
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ldr r1, =ftrace_graph_return
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ldr r2, [r1]
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cmp r0, r2
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bne ftrace_graph_caller\suffix
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ldr r1, =ftrace_graph_entry
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ldr r2, [r1]
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ldr r0, =ftrace_graph_entry_stub
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cmp r0, r2
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bne ftrace_graph_caller\suffix
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#endif
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mcount_exit
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1: mcount_get_lr r1 @ lr of instrumented func
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mcount_adjust_addr r0, lr @ instrumented function
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badr lr, 2f
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mov pc, r2
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2: mcount_exit
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.endm
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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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.globl ftrace_call\suffix
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ftrace_call\suffix:
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bl ftrace_stub
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.globl ftrace_graph_call\suffix
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ftrace_graph_call\suffix:
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mov r0, r0
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#endif
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mcount_exit
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.endm
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.macro __ftrace_graph_caller
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sub r0, fp, #4 @ &lr of instrumented routine (&parent)
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#ifdef CONFIG_DYNAMIC_FTRACE
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@ called from __ftrace_caller, saved in mcount_enter
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ldr r1, [sp, #16] @ instrumented routine (func)
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mcount_adjust_addr r1, r1
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#else
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@ called from __mcount, untouched in lr
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mcount_adjust_addr r1, lr @ instrumented routine (func)
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#endif
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mov r2, fp @ frame pointer
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bl prepare_ftrace_return
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mcount_exit
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.endm
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#ifdef CONFIG_OLD_MCOUNT
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/*
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* mcount
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*/
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.macro mcount_enter
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stmdb sp!, {r0-r3, lr}
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.endm
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.macro mcount_get_lr reg
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ldr \reg, [fp, #-4]
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.endm
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.macro mcount_exit
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ldr lr, [fp, #-4]
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ldmia sp!, {r0-r3, pc}
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.endm
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ENTRY(mcount)
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#ifdef CONFIG_DYNAMIC_FTRACE
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stmdb sp!, {lr}
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ldr lr, [fp, #-4]
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ldmia sp!, {pc}
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#else
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__mcount _old
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#endif
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ENDPROC(mcount)
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(ftrace_caller_old)
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__ftrace_caller _old
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ENDPROC(ftrace_caller_old)
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ENTRY(ftrace_graph_caller_old)
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__ftrace_graph_caller
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ENDPROC(ftrace_graph_caller_old)
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#endif
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.purgem mcount_enter
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.purgem mcount_get_lr
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.purgem mcount_exit
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#endif
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/*
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* __gnu_mcount_nc
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*/
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.macro mcount_enter
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/*
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* This pad compensates for the push {lr} at the call site. Note that we are
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* unable to unwind through a function which does not otherwise save its lr.
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*/
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UNWIND(.pad #4)
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stmdb sp!, {r0-r3, lr}
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UNWIND(.save {r0-r3, lr})
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.endm
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.macro mcount_get_lr reg
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ldr \reg, [sp, #20]
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.endm
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.macro mcount_exit
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ldmia sp!, {r0-r3, ip, lr}
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ret ip
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.endm
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ENTRY(__gnu_mcount_nc)
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UNWIND(.fnstart)
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#ifdef CONFIG_DYNAMIC_FTRACE
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mov ip, lr
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ldmia sp!, {lr}
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ret ip
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#else
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__mcount
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#endif
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UNWIND(.fnend)
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ENDPROC(__gnu_mcount_nc)
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(ftrace_caller)
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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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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ENTRY(ftrace_graph_caller)
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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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#endif
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.purgem mcount_enter
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.purgem mcount_get_lr
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.purgem mcount_exit
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.globl return_to_handler
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return_to_handler:
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stmdb sp!, {r0-r3}
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mov r0, fp @ frame pointer
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bl ftrace_return_to_handler
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mov lr, r0 @ r0 has real ret addr
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ldmia sp!, {r0-r3}
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ret lr
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#endif
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ENTRY(ftrace_stub)
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.Lftrace_stub:
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ret lr
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ENDPROC(ftrace_stub)
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