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linux/arch/arm64/kernel/entry-ftrace.S
Mark Rutland 0d8116ccd8 arm64: ftrace: remove redundant label 
Since commit:

  c4a0ebf87c ("arm64/ftrace: Make function graph use ftrace directly")

The 'ftrace_common_return' label has been unused.

Remove it.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Will Deacon <will@kernel.org>
Tested-by: "Ivan T. Ivanov" <iivanov@suse.de>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220614080944.1349146-4-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2022-06-15 16:14:47 +01:00

330 lines
9.0 KiB
ArmAsm
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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* arch/arm64/kernel/entry-ftrace.S
*
* Copyright (C) 2013 Linaro Limited
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
*/
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/assembler.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
/*
* Due to -fpatchable-function-entry=2, the compiler has placed two NOPs before
* the regular function prologue. For an enabled callsite, ftrace_init_nop() and
* ftrace_make_call() have patched those NOPs to:
*
* MOV X9, LR
* BL <entry>
*
* ... where <entry> is either ftrace_caller or ftrace_regs_caller.
*
* Each instrumented function follows the AAPCS, so here x0-x8 and x18-x30 are
* live (x18 holds the Shadow Call Stack pointer), and x9-x17 are safe to
* clobber.
*
* We save the callsite's context into a pt_regs before invoking any ftrace
* callbacks. So that we can get a sensible backtrace, we create a stack record
* for the callsite and the ftrace entry assembly. This is not sufficient for
* reliable stacktrace: until we create the callsite stack record, its caller
* is missing from the LR and existing chain of frame records.
*/
.macro ftrace_regs_entry, allregs=0
/* Make room for pt_regs, plus a callee frame */
sub sp, sp, #(PT_REGS_SIZE + 16)
/* Save function arguments (and x9 for simplicity) */
stp x0, x1, [sp, #S_X0]
stp x2, x3, [sp, #S_X2]
stp x4, x5, [sp, #S_X4]
stp x6, x7, [sp, #S_X6]
stp x8, x9, [sp, #S_X8]
/* Optionally save the callee-saved registers, always save the FP */
.if \allregs == 1
stp x10, x11, [sp, #S_X10]
stp x12, x13, [sp, #S_X12]
stp x14, x15, [sp, #S_X14]
stp x16, x17, [sp, #S_X16]
stp x18, x19, [sp, #S_X18]
stp x20, x21, [sp, #S_X20]
stp x22, x23, [sp, #S_X22]
stp x24, x25, [sp, #S_X24]
stp x26, x27, [sp, #S_X26]
stp x28, x29, [sp, #S_X28]
.else
str x29, [sp, #S_FP]
.endif
/* Save the callsite's SP and LR */
add x10, sp, #(PT_REGS_SIZE + 16)
stp x9, x10, [sp, #S_LR]
/* Save the PC after the ftrace callsite */
str x30, [sp, #S_PC]
/* Create a frame record for the callsite above pt_regs */
stp x29, x9, [sp, #PT_REGS_SIZE]
add x29, sp, #PT_REGS_SIZE
/* Create our frame record within pt_regs. */
stp x29, x30, [sp, #S_STACKFRAME]
add x29, sp, #S_STACKFRAME
.endm
SYM_CODE_START(ftrace_regs_caller)
bti c
ftrace_regs_entry 1
b ftrace_common
SYM_CODE_END(ftrace_regs_caller)
SYM_CODE_START(ftrace_caller)
bti c
ftrace_regs_entry 0
b ftrace_common
SYM_CODE_END(ftrace_caller)
SYM_CODE_START(ftrace_common)
sub x0, x30, #AARCH64_INSN_SIZE // ip (callsite's BL insn)
mov x1, x9 // parent_ip (callsite's LR)
ldr_l x2, function_trace_op // op
mov x3, sp // regs
SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
bl ftrace_stub
/*
* At the callsite x0-x8 and x19-x30 were live. Any C code will have preserved
* x19-x29 per the AAPCS, and we created frame records upon entry, so we need
* to restore x0-x8, x29, and x30.
*/
/* Restore function arguments */
ldp x0, x1, [sp]
ldp x2, x3, [sp, #S_X2]
ldp x4, x5, [sp, #S_X4]
ldp x6, x7, [sp, #S_X6]
ldr x8, [sp, #S_X8]
/* Restore the callsite's FP, LR, PC */
ldr x29, [sp, #S_FP]
ldr x30, [sp, #S_LR]
ldr x9, [sp, #S_PC]
/* Restore the callsite's SP */
add sp, sp, #PT_REGS_SIZE + 16
ret x9
SYM_CODE_END(ftrace_common)
#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
/*
* Gcc with -pg will put the following code in the beginning of each function:
* mov x0, x30
* bl _mcount
* [function's body ...]
* "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic
* ftrace is enabled.
*
* Please note that x0 as an argument will not be used here because we can
* get lr(x30) of instrumented function at any time by winding up call stack
* as long as the kernel is compiled without -fomit-frame-pointer.
* (or CONFIG_FRAME_POINTER, this is forced on arm64)
*
* stack layout after mcount_enter in _mcount():
*
* current sp/fp => 0:+-----+
* in _mcount() | x29 | -> instrumented function's fp
* +-----+
* | x30 | -> _mcount()'s lr (= instrumented function's pc)
* old sp => +16:+-----+
* when instrumented | |
* function calls | ... |
* _mcount() | |
* | |
* instrumented => +xx:+-----+
* function's fp | x29 | -> parent's fp
* +-----+
* | x30 | -> instrumented function's lr (= parent's pc)
* +-----+
* | ... |
*/
.macro mcount_enter
stp x29, x30, [sp, #-16]!
mov x29, sp
.endm
.macro mcount_exit
ldp x29, x30, [sp], #16
ret
.endm
.macro mcount_adjust_addr rd, rn
sub \rd, \rn, #AARCH64_INSN_SIZE
.endm
/* for instrumented function's parent */
.macro mcount_get_parent_fp reg
ldr \reg, [x29]
ldr \reg, [\reg]
.endm
/* for instrumented function */
.macro mcount_get_pc0 reg
mcount_adjust_addr \reg, x30
.endm
.macro mcount_get_pc reg
ldr \reg, [x29, #8]
mcount_adjust_addr \reg, \reg
.endm
.macro mcount_get_lr reg
ldr \reg, [x29]
ldr \reg, [\reg, #8]
.endm
.macro mcount_get_lr_addr reg
ldr \reg, [x29]
add \reg, \reg, #8
.endm
#ifndef CONFIG_DYNAMIC_FTRACE
/*
* void _mcount(unsigned long return_address)
* @return_address: return address to instrumented function
*
* This function makes calls, if enabled, to:
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
SYM_FUNC_START(_mcount)
mcount_enter
ldr_l x2, ftrace_trace_function
adr x0, ftrace_stub
cmp x0, x2 // if (ftrace_trace_function
b.eq skip_ftrace_call // != ftrace_stub) {
mcount_get_pc x0 // function's pc
mcount_get_lr x1 // function's lr (= parent's pc)
blr x2 // (*ftrace_trace_function)(pc, lr);
skip_ftrace_call: // }
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ldr_l x2, ftrace_graph_return
cmp x0, x2 // if ((ftrace_graph_return
b.ne ftrace_graph_caller // != ftrace_stub)
ldr_l x2, ftrace_graph_entry // || (ftrace_graph_entry
adr_l x0, ftrace_graph_entry_stub // != ftrace_graph_entry_stub))
cmp x0, x2
b.ne ftrace_graph_caller // ftrace_graph_caller();
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
mcount_exit
SYM_FUNC_END(_mcount)
EXPORT_SYMBOL(_mcount)
NOKPROBE(_mcount)
#else /* CONFIG_DYNAMIC_FTRACE */
/*
* _mcount() is used to build the kernel with -pg option, but all the branch
* instructions to _mcount() are replaced to NOP initially at kernel start up,
* and later on, NOP to branch to ftrace_caller() when enabled or branch to
* NOP when disabled per-function base.
*/
SYM_FUNC_START(_mcount)
ret
SYM_FUNC_END(_mcount)
EXPORT_SYMBOL(_mcount)
NOKPROBE(_mcount)
/*
* void ftrace_caller(unsigned long return_address)
* @return_address: return address to instrumented function
*
* This function is a counterpart of _mcount() in 'static' ftrace, and
* makes calls to:
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
SYM_FUNC_START(ftrace_caller)
mcount_enter
mcount_get_pc0 x0 // function's pc
mcount_get_lr x1 // function's lr
SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) // tracer(pc, lr);
nop // This will be replaced with "bl xxx"
// where xxx can be any kind of tracer.
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller();
nop // If enabled, this will be replaced
// "b ftrace_graph_caller"
#endif
mcount_exit
SYM_FUNC_END(ftrace_caller)
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* void ftrace_graph_caller(void)
*
* Called from _mcount() or ftrace_caller() when function_graph tracer is
* selected.
* This function w/ prepare_ftrace_return() fakes link register's value on
* the call stack in order to intercept instrumented function's return path
* and run return_to_handler() later on its exit.
*/
SYM_FUNC_START(ftrace_graph_caller)
mcount_get_pc x0 // function's pc
mcount_get_lr_addr x1 // pointer to function's saved lr
mcount_get_parent_fp x2 // parent's fp
bl prepare_ftrace_return // prepare_ftrace_return(pc, &lr, fp)
mcount_exit
SYM_FUNC_END(ftrace_graph_caller)
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
SYM_FUNC_START(ftrace_stub)
ret
SYM_FUNC_END(ftrace_stub)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* void return_to_handler(void)
*
* Run ftrace_return_to_handler() before going back to parent.
* @fp is checked against the value passed by ftrace_graph_caller().
*/
SYM_CODE_START(return_to_handler)
/* save return value regs */
sub sp, sp, #64
stp x0, x1, [sp]
stp x2, x3, [sp, #16]
stp x4, x5, [sp, #32]
stp x6, x7, [sp, #48]
mov x0, x29 // parent's fp
bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
mov x30, x0 // restore the original return address
/* restore return value regs */
ldp x0, x1, [sp]
ldp x2, x3, [sp, #16]
ldp x4, x5, [sp, #32]
ldp x6, x7, [sp, #48]
add sp, sp, #64
ret
SYM_CODE_END(return_to_handler)
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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