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linux/arch/arm/kernel/entry-ftrace.S
Linus Walleij a9a058031c ARM: 9382/1: ftrace: Define ftrace_stub_graph 
Several architectures defines this stub for the graph tracer,
and it is needed for CFI, as it needs a separate symbol for it.
The trick from include/asm-generic/vmlinux.lds.h to define
ftrace_stub_graph to ftrace_stub isn't working when using CFI.
Commit 883bbbffa5 contains the details.

Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
2024-04-18 12:12:18 +01:00

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/* SPDX-License-Identifier: GPL-2.0-only */
#include <asm/assembler.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
#include "entry-header.S"
/*
* When compiling with -pg, gcc inserts a call to the mcount routine at the
* start of every function. In mcount, apart from the function's address (in
* lr), we need to get hold of the function's caller's address.
*
* Newer GCCs (4.4+) solve this problem by using a version of mcount with call
* sites like:
*
* push {lr}
* bl __gnu_mcount_nc
*
* With these compilers, frame pointers are not necessary.
*
* mcount can be thought of as a function called in the middle of a subroutine
* call. As such, it needs to be transparent for both the caller and the
* callee: the original lr needs to be restored when leaving mcount, and no
* registers should be clobbered.
*
* When using dynamic ftrace, we patch out the mcount call by a "add sp, #4"
* instead of the __gnu_mcount_nc call (see arch/arm/kernel/ftrace.c).
*/
.macro mcount_adjust_addr rd, rn
bic \rd, \rn, #1 @ clear the Thumb bit if present
sub \rd, \rd, #MCOUNT_INSN_SIZE
.endm
.macro __mcount suffix
mcount_enter
ldr_va r2, ftrace_trace_function
badr r0, .Lftrace_stub
cmp r0, r2
bne 1f
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ldr_va r2, ftrace_graph_return
cmp r0, r2
bne ftrace_graph_caller\suffix
ldr_va r2, ftrace_graph_entry
mov_l r0, ftrace_graph_entry_stub
cmp r0, r2
bne ftrace_graph_caller\suffix
#endif
mcount_exit
1: mcount_get_lr r1 @ lr of instrumented func
mcount_adjust_addr r0, lr @ instrumented function
badr lr, 2f
mov pc, r2
2: mcount_exit
.endm
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
.macro __ftrace_regs_caller
str lr, [sp, #-8]! @ store LR as PC and make space for CPSR/OLD_R0,
@ OLD_R0 will overwrite previous LR
ldr lr, [sp, #8] @ get previous LR
str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR
str lr, [sp, #-4]! @ store previous LR as LR
add lr, sp, #16 @ move in LR the value of SP as it was
@ before the push {lr} of the mcount mechanism
push {r0-r11, ip, lr}
@ stack content at this point:
@ 0 4 48 52 56 60 64 68 72
@ R0 | R1 | ... | IP | SP + 4 | previous LR | LR | PSR | OLD_R0 |
mov r3, sp @ struct pt_regs*
ldr_va r2, function_trace_op @ pointer to the current
@ function tracing op
ldr r1, [sp, #S_LR] @ lr of instrumented func
ldr lr, [sp, #S_PC] @ get LR
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:
ARM( mov r0, r0 )
THUMB( nop.w )
#endif
@ pop saved regs
pop {r0-r11, ip, lr} @ restore r0 through r12
ldr lr, [sp], #4 @ restore LR
ldr pc, [sp], #12
.endm
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.macro __ftrace_graph_regs_caller
#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)
mcount_adjust_addr r1, r1
mov r2, fpreg @ frame pointer
add r3, sp, #PT_REGS_SIZE
bl prepare_ftrace_return
@ pop registers saved in ftrace_regs_caller
pop {r0-r11, ip, lr} @ restore r0 through r12
ldr lr, [sp], #4 @ restore LR
ldr pc, [sp], #12
.endm
#endif
#endif
.macro __ftrace_caller suffix
mcount_enter
mcount_get_lr r1 @ lr of instrumented func
mcount_adjust_addr r0, lr @ instrumented function
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
ldr_va r2, function_trace_op @ pointer to the current
@ function tracing op
mov r3, #0 @ regs is NULL
#endif
.globl ftrace_call\suffix
ftrace_call\suffix:
bl ftrace_stub
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call\suffix
ftrace_graph_call\suffix:
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)
mcount_adjust_addr r1, r1
#else
@ called from __mcount, untouched in lr
mcount_adjust_addr r1, lr @ instrumented routine (func)
#endif
mov r2, fpreg @ frame pointer
add r3, sp, #24
bl prepare_ftrace_return
mcount_exit
.endm
/*
* __gnu_mcount_nc
*/
.macro mcount_enter
/*
* This pad compensates for the push {lr} at the call site. Note that we are
* unable to unwind through a function which does not otherwise save its lr.
*/
UNWIND(.pad #4)
stmdb sp!, {r0-r3, lr}
UNWIND(.save {r0-r3, lr})
.endm
.macro mcount_get_lr reg
ldr \reg, [sp, #20]
.endm
.macro mcount_exit
ldmia sp!, {r0-r3}
ldr lr, [sp, #4]
ldr pc, [sp], #8
.endm
ENTRY(__gnu_mcount_nc)
UNWIND(.fnstart)
#ifdef CONFIG_DYNAMIC_FTRACE
push {lr}
ldr lr, [sp, #4]
ldr pc, [sp], #8
#else
__mcount
#endif
UNWIND(.fnend)
ENDPROC(__gnu_mcount_nc)
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(ftrace_caller)
UNWIND(.fnstart)
__ftrace_caller
UNWIND(.fnend)
ENDPROC(ftrace_caller)
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
ENTRY(ftrace_regs_caller)
UNWIND(.fnstart)
__ftrace_regs_caller
UNWIND(.fnend)
ENDPROC(ftrace_regs_caller)
#endif
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
UNWIND(.fnstart)
__ftrace_graph_caller
UNWIND(.fnend)
ENDPROC(ftrace_graph_caller)
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
ENTRY(ftrace_graph_regs_caller)
UNWIND(.fnstart)
__ftrace_graph_regs_caller
UNWIND(.fnend)
ENDPROC(ftrace_graph_regs_caller)
#endif
#endif
.purgem mcount_enter
.purgem mcount_get_lr
.purgem mcount_exit
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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)
.Lftrace_stub:
ret lr
ENDPROC(ftrace_stub)
ENTRY(ftrace_stub_graph)
ret lr
ENDPROC(ftrace_stub_graph)
#ifdef CONFIG_DYNAMIC_FTRACE
__INIT
.macro init_tramp, dst:req
ENTRY(\dst\()_from_init)
ldr pc, =\dst
ENDPROC(\dst\()_from_init)
.endm
init_tramp ftrace_caller
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
init_tramp ftrace_regs_caller
#endif
#endif
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