2019-06-04 16:11:33 +08:00
|
|
|
/* SPDX-License-Identifier: GPL-2.0-only */
|
2014-04-30 17:54:33 +08:00
|
|
|
/*
|
|
|
|
|
* arch/arm64/kernel/entry-ftrace.S
|
|
|
|
|
*
|
|
|
|
|
* Copyright (C) 2013 Linaro Limited
|
|
|
|
|
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#include <linux/linkage.h>
|
arm64: implement ftrace with regs
This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.
Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).
For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:
| unsigned long bar(void);
|
| unsigned long foo(void)
| {
| return bar() + 1;
| }
... to:
| <foo>:
| nop
| nop
| stp x29, x30, [sp, #-16]!
| mov x29, sp
| bl 0 <bar>
| add x0, x0, #0x1
| ldp x29, x30, [sp], #16
| ret
This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:
| mov x9, x30
| bl <ftrace-entry>
Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.
There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.
Signed-off-by: Torsten Duwe <duwe@suse.de>
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>
Cc: Will Deacon <will@kernel.org>
2019-02-08 23:10:19 +08:00
|
|
|
#include <asm/asm-offsets.h>
|
2017-02-15 05:32:58 +08:00
|
|
|
#include <asm/assembler.h>
|
2014-04-30 17:54:33 +08:00
|
|
|
#include <asm/ftrace.h>
|
|
|
|
|
#include <asm/insn.h>
|
|
|
|
|
|
arm64: implement ftrace with regs
This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.
Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).
For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:
| unsigned long bar(void);
|
| unsigned long foo(void)
| {
| return bar() + 1;
| }
... to:
| <foo>:
| nop
| nop
| stp x29, x30, [sp, #-16]!
| mov x29, sp
| bl 0 <bar>
| add x0, x0, #0x1
| ldp x29, x30, [sp], #16
| ret
This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:
| mov x9, x30
| bl <ftrace-entry>
Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.
There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.
Signed-off-by: Torsten Duwe <duwe@suse.de>
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>
Cc: Will Deacon <will@kernel.org>
2019-02-08 23:10:19 +08:00
|
|
|
#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 x19-x30 are
|
|
|
|
|
* live, and x9-x18 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, #(S_FRAME_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, #(S_FRAME_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, #S_FRAME_SIZE]
|
|
|
|
|
add x29, sp, #S_FRAME_SIZE
|
|
|
|
|
|
|
|
|
|
/* Create our frame record within pt_regs. */
|
|
|
|
|
stp x29, x30, [sp, #S_STACKFRAME]
|
|
|
|
|
add x29, sp, #S_STACKFRAME
|
|
|
|
|
.endm
|
|
|
|
|
|
|
|
|
|
ENTRY(ftrace_regs_caller)
|
|
|
|
|
ftrace_regs_entry 1
|
|
|
|
|
b ftrace_common
|
|
|
|
|
ENDPROC(ftrace_regs_caller)
|
|
|
|
|
|
|
|
|
|
ENTRY(ftrace_caller)
|
|
|
|
|
ftrace_regs_entry 0
|
|
|
|
|
b ftrace_common
|
|
|
|
|
ENDPROC(ftrace_caller)
|
|
|
|
|
|
|
|
|
|
ENTRY(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
|
|
|
|
|
|
|
|
|
|
GLOBAL(ftrace_call)
|
|
|
|
|
bl ftrace_stub
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
|
|
|
|
GLOBAL(ftrace_graph_call) // ftrace_graph_caller();
|
|
|
|
|
nop // If enabled, this will be replaced
|
|
|
|
|
// "b ftrace_graph_caller"
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* 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.
|
|
|
|
|
*/
|
|
|
|
|
ftrace_common_return:
|
|
|
|
|
/* 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, #S_FRAME_SIZE + 16
|
|
|
|
|
|
|
|
|
|
ret x9
|
|
|
|
|
ENDPROC(ftrace_common)
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
|
|
|
|
ENTRY(ftrace_graph_caller)
|
|
|
|
|
ldr x0, [sp, #S_PC]
|
|
|
|
|
sub x0, x0, #AARCH64_INSN_SIZE // ip (callsite's BL insn)
|
|
|
|
|
add x1, sp, #S_LR // parent_ip (callsite's LR)
|
|
|
|
|
ldr x2, [sp, #S_FRAME_SIZE] // parent fp (callsite's FP)
|
|
|
|
|
bl prepare_ftrace_return
|
|
|
|
|
b ftrace_common_return
|
|
|
|
|
ENDPROC(ftrace_graph_caller)
|
|
|
|
|
#else
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
|
|
|
|
|
|
2014-04-30 17:54:33 +08:00
|
|
|
/*
|
|
|
|
|
* 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
|
|
|
|
|
|
2014-04-30 17:54:34 +08:00
|
|
|
#ifndef CONFIG_DYNAMIC_FTRACE
|
2014-04-30 17:54:33 +08:00
|
|
|
/*
|
|
|
|
|
* 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
|
|
|
|
|
*/
|
|
|
|
|
ENTRY(_mcount)
|
|
|
|
|
mcount_enter
|
|
|
|
|
|
2017-01-18 00:10:58 +08:00
|
|
|
ldr_l x2, ftrace_trace_function
|
2014-04-30 17:54:33 +08:00
|
|
|
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);
|
|
|
|
|
|
2017-11-03 19:44:16 +08:00
|
|
|
skip_ftrace_call: // }
|
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
2017-01-18 00:10:58 +08:00
|
|
|
ldr_l x2, ftrace_graph_return
|
2014-11-07 22:12:33 +08:00
|
|
|
cmp x0, x2 // if ((ftrace_graph_return
|
|
|
|
|
b.ne ftrace_graph_caller // != ftrace_stub)
|
|
|
|
|
|
2017-01-18 00:10:58 +08:00
|
|
|
ldr_l x2, ftrace_graph_entry // || (ftrace_graph_entry
|
|
|
|
|
adr_l x0, ftrace_graph_entry_stub // != ftrace_graph_entry_stub))
|
2014-04-30 17:54:33 +08:00
|
|
|
cmp x0, x2
|
|
|
|
|
b.ne ftrace_graph_caller // ftrace_graph_caller();
|
|
|
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
2017-11-03 19:44:16 +08:00
|
|
|
mcount_exit
|
2014-04-30 17:54:33 +08:00
|
|
|
ENDPROC(_mcount)
|
2018-12-08 02:08:22 +08:00
|
|
|
EXPORT_SYMBOL(_mcount)
|
|
|
|
|
NOKPROBE(_mcount)
|
2014-04-30 17:54:33 +08:00
|
|
|
|
2014-04-30 17:54:34 +08:00
|
|
|
#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.
|
|
|
|
|
*/
|
|
|
|
|
ENTRY(_mcount)
|
|
|
|
|
ret
|
|
|
|
|
ENDPROC(_mcount)
|
2018-12-08 02:08:22 +08:00
|
|
|
EXPORT_SYMBOL(_mcount)
|
|
|
|
|
NOKPROBE(_mcount)
|
2014-04-30 17:54:34 +08:00
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* 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
|
|
|
|
|
*/
|
|
|
|
|
ENTRY(ftrace_caller)
|
|
|
|
|
mcount_enter
|
|
|
|
|
|
|
|
|
|
mcount_get_pc0 x0 // function's pc
|
|
|
|
|
mcount_get_lr x1 // function's lr
|
|
|
|
|
|
2018-11-16 06:41:59 +08:00
|
|
|
GLOBAL(ftrace_call) // tracer(pc, lr);
|
2014-04-30 17:54:34 +08:00
|
|
|
nop // This will be replaced with "bl xxx"
|
|
|
|
|
// where xxx can be any kind of tracer.
|
|
|
|
|
|
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
2018-11-16 06:41:59 +08:00
|
|
|
GLOBAL(ftrace_graph_call) // ftrace_graph_caller();
|
2014-04-30 17:54:34 +08:00
|
|
|
nop // If enabled, this will be replaced
|
|
|
|
|
// "b ftrace_graph_caller"
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
mcount_exit
|
|
|
|
|
ENDPROC(ftrace_caller)
|
2014-04-30 17:54:33 +08:00
|
|
|
|
|
|
|
|
#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.
|
|
|
|
|
*/
|
|
|
|
|
ENTRY(ftrace_graph_caller)
|
2018-11-16 06:42:03 +08:00
|
|
|
mcount_get_pc x0 // function's pc
|
|
|
|
|
mcount_get_lr_addr x1 // pointer to function's saved lr
|
2014-04-30 17:54:33 +08:00
|
|
|
mcount_get_parent_fp x2 // parent's fp
|
2018-11-16 06:42:03 +08:00
|
|
|
bl prepare_ftrace_return // prepare_ftrace_return(pc, &lr, fp)
|
2014-04-30 17:54:33 +08:00
|
|
|
|
|
|
|
|
mcount_exit
|
|
|
|
|
ENDPROC(ftrace_graph_caller)
|
arm64: implement ftrace with regs
This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.
Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).
For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:
| unsigned long bar(void);
|
| unsigned long foo(void)
| {
| return bar() + 1;
| }
... to:
| <foo>:
| nop
| nop
| stp x29, x30, [sp, #-16]!
| mov x29, sp
| bl 0 <bar>
| add x0, x0, #0x1
| ldp x29, x30, [sp], #16
| ret
This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:
| mov x9, x30
| bl <ftrace-entry>
Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.
There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.
Signed-off-by: Torsten Duwe <duwe@suse.de>
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>
Cc: Will Deacon <will@kernel.org>
2019-02-08 23:10:19 +08:00
|
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
|
|
|
|
#endif /* CONFIG_DYNAMIC_FTRACE */
|
|
|
|
|
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
|
|
|
|
|
|
|
|
|
|
ENTRY(ftrace_stub)
|
|
|
|
|
ret
|
|
|
|
|
ENDPROC(ftrace_stub)
|
2014-04-30 17:54:33 +08:00
|
|
|
|
arm64: implement ftrace with regs
This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.
Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).
For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:
| unsigned long bar(void);
|
| unsigned long foo(void)
| {
| return bar() + 1;
| }
... to:
| <foo>:
| nop
| nop
| stp x29, x30, [sp, #-16]!
| mov x29, sp
| bl 0 <bar>
| add x0, x0, #0x1
| ldp x29, x30, [sp], #16
| ret
This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:
| mov x9, x30
| bl <ftrace-entry>
Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.
There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.
Signed-off-by: Torsten Duwe <duwe@suse.de>
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>
Cc: Will Deacon <will@kernel.org>
2019-02-08 23:10:19 +08:00
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
2014-04-30 17:54:33 +08:00
|
|
|
/*
|
|
|
|
|
* void return_to_handler(void)
|
|
|
|
|
*
|
|
|
|
|
* Run ftrace_return_to_handler() before going back to parent.
|
2018-11-16 06:42:00 +08:00
|
|
|
* @fp is checked against the value passed by ftrace_graph_caller().
|
2014-04-30 17:54:33 +08:00
|
|
|
*/
|
|
|
|
|
ENTRY(return_to_handler)
|
2018-11-16 06:42:02 +08:00
|
|
|
/* 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]
|
|
|
|
|
|
2014-04-30 17:54:33 +08:00
|
|
|
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
|
2018-11-16 06:42:02 +08:00
|
|
|
|
|
|
|
|
/* 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
|
|
|
|
|
|
2014-04-30 17:54:33 +08:00
|
|
|
ret
|
|
|
|
|
END(return_to_handler)
|
|
|
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|