Re: [PATCH 1/3] ftrace: introdue ftrace_call_init

From: Jisheng Zhang
Date: Mon Aug 26 2019 - 06:14:18 EST

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Hi all,

On Tue, 20 Aug 2019 11:27:38 +0200 (CEST) Miroslav Benes wrote:

>
> Hi,
>
> On Mon, 19 Aug 2019, Jisheng Zhang wrote:
>
> > On some arch, the FTRACE_WITH_REGS is implemented with gcc's
> > -fpatchable-function-entry (=2), gcc adds 2 NOPs at the beginning
> > of each function, so this makes the MCOUNT_ADDR useless. In ftrace
> > common framework, MCOUNT_ADDR is mostly used to "init" the nop, so
> > let's introcude ftrace_call_init().
> >
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx>
> > ---
> > include/linux/ftrace.h | 1 +
> > kernel/trace/ftrace.c | 4 ++++
> > 2 files changed, 5 insertions(+)
> >
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 8a8cb3c401b2..8175ffb671f0 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -458,6 +458,7 @@ extern void ftrace_regs_caller(void);
> > extern void ftrace_call(void);
> > extern void ftrace_regs_call(void);
> > extern void mcount_call(void);
> > +extern int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec);
> >
> > void ftrace_modify_all_code(int command);
> >
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index eca34503f178..9df5a66a6811 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -2500,7 +2500,11 @@ ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
> > if (unlikely(ftrace_disabled))
> > return 0;
> >
> > +#ifdef MCOUNT_ADDR
> > ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
> > +#else
> > + ret = ftrace_call_init(mod, rec);
> > +#endif
> > if (ret) {
> > ftrace_bug_type = FTRACE_BUG_INIT;
> > ftrace_bug(ret, rec);
>
> I may be missing something, but the patch does not seem to be complete.
> There is no ftrace_call_init() implemented. MCOUNT_ADDR is still defined,
> so it does not change much. I don't think it is what Mark had in his mind.
>

Here is patch to remove MCOUNT_ADDR from all arch, but I think it isn't
as good as current MCOUNT_ADDR. So how to remove the MCOUNT_ADDR depedency?
Could we

patch ftrace_make_nop to accept one more parameter? I.E
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr, bool init)

or

make "0" a special meaning to tell ftrace_make_nop to "init"?

Thanks

<---8

ftrace: introdue ftrace_call_init

On some arch, the FTRACE_WITH_REGS is implemented with gcc's
-fpatchable-function-entry (=2), gcc adds 2 NOPs at the beginning
of each function, so this makes the MCOUNT_ADDR useless. In ftrace
common framework, MCOUNT_ADDR is mostly used to "init" the nop, so
let's introcude ftrace_call_init() and remove MCOUNT_ADDR.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx>
---
arch/arm/include/asm/ftrace.h | 1 -
arch/arm/kernel/ftrace.c | 5 +++++
arch/arm64/include/asm/ftrace.h | 1 -
arch/arm64/kernel/ftrace.c | 5 +++++
arch/csky/kernel/ftrace.c | 5 +++++
arch/ia64/include/asm/ftrace.h | 2 --
arch/ia64/kernel/ftrace.c | 5 +++++
arch/microblaze/include/asm/ftrace.h | 1 -
arch/microblaze/kernel/ftrace.c | 5 +++++
arch/mips/include/asm/ftrace.h | 1 -
arch/mips/kernel/ftrace.c | 9 +++++++--
arch/nds32/include/asm/ftrace.h | 1 -
arch/nds32/kernel/ftrace.c | 5 +++++
arch/parisc/include/asm/ftrace.h | 1 -
arch/parisc/kernel/ftrace.c | 5 +++++
arch/powerpc/include/asm/ftrace.h | 1 -
arch/powerpc/kernel/trace/ftrace.c | 5 +++++
arch/riscv/include/asm/ftrace.h | 1 -
arch/riscv/kernel/ftrace.c | 5 +++++
arch/s390/include/asm/ftrace.h | 1 -
arch/s390/kernel/ftrace.c | 22 +++++++++++++++++-----
arch/sh/include/asm/ftrace.h | 2 --
arch/sh/kernel/ftrace.c | 5 +++++
arch/sparc/include/asm/ftrace.h | 1 -
arch/sparc/kernel/ftrace.c | 5 +++++
arch/x86/include/asm/ftrace.h | 1 -
arch/x86/kernel/ftrace.c | 28 +++++++++++++++-------------
arch/xtensa/include/asm/ftrace.h | 1 -
include/linux/ftrace.h | 1 +
kernel/trace/ftrace.c | 2 +-
30 files changed, 96 insertions(+), 37 deletions(-)

diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 18b0197f2384..afb01ab7f956 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -7,7 +7,6 @@
#endif

#ifdef CONFIG_FUNCTION_TRACER
-#define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */

#ifndef __ASSEMBLY__
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index bda949fd84e8..fd3547bb4bfa 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -172,6 +172,11 @@ int ftrace_make_nop(struct module *mod,
return ret;
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)__gnu_mcount_nc);
+}
+
int __init ftrace_dyn_arch_init(void)
{
return 0;
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 5ab5200b2bdc..de6f35ef3825 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -11,7 +11,6 @@
#include <asm/insn.h>

#define HAVE_FUNCTION_GRAPH_FP_TEST
-#define MCOUNT_ADDR ((unsigned long)_mcount)
#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE

#ifndef __ASSEMBLY__
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 171773257974..8298b8a7d8f6 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -196,6 +196,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return ftrace_modify_code(pc, old, new, validate);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
void arch_ftrace_update_code(int command)
{
command |= FTRACE_MAY_SLEEP;
diff --git a/arch/csky/kernel/ftrace.c b/arch/csky/kernel/ftrace.c
index 44f4880179b7..c1fce15caaa4 100644
--- a/arch/csky/kernel/ftrace.c
+++ b/arch/csky/kernel/ftrace.c
@@ -122,6 +122,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return ftrace_modify_code(rec->ip, addr, false, false);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = ftrace_modify_code((unsigned long)&ftrace_call,
diff --git a/arch/ia64/include/asm/ftrace.h b/arch/ia64/include/asm/ftrace.h
index a07a8e575453..2aefd2098fc5 100644
--- a/arch/ia64/include/asm/ftrace.h
+++ b/arch/ia64/include/asm/ftrace.h
@@ -9,8 +9,6 @@
extern void _mcount(unsigned long pfs, unsigned long r1, unsigned long b0, unsigned long r0);
#define mcount _mcount

-/* In IA64, MCOUNT_ADDR is set in link time, so it's not a constant at compile time */
-#define MCOUNT_ADDR (((struct fnptr *)mcount)->ip)
#define FTRACE_ADDR (((struct fnptr *)ftrace_caller)->ip)

static inline unsigned long ftrace_call_adjust(unsigned long addr)
diff --git a/arch/ia64/kernel/ftrace.c b/arch/ia64/kernel/ftrace.c
index cee411e647ca..0cb2cbcea4fc 100644
--- a/arch/ia64/kernel/ftrace.c
+++ b/arch/ia64/kernel/ftrace.c
@@ -169,6 +169,11 @@ int ftrace_make_nop(struct module *mod,
return ftrace_modify_code(rec->ip, NULL, new, 0);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, ((struct fnptr *)mcount)->ip);
+}
+
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
diff --git a/arch/microblaze/include/asm/ftrace.h b/arch/microblaze/include/asm/ftrace.h
index 5db7f4489f05..02d185ef22fe 100644
--- a/arch/microblaze/include/asm/ftrace.h
+++ b/arch/microblaze/include/asm/ftrace.h
@@ -4,7 +4,6 @@

#ifdef CONFIG_FUNCTION_TRACER

-#define MCOUNT_ADDR ((unsigned long)(_mcount))
#define MCOUNT_INSN_SIZE 8 /* sizeof mcount call */

#ifndef __ASSEMBLY__
diff --git a/arch/microblaze/kernel/ftrace.c b/arch/microblaze/kernel/ftrace.c
index 224eea40e1ee..f3606e3cba94 100644
--- a/arch/microblaze/kernel/ftrace.c
+++ b/arch/microblaze/kernel/ftrace.c
@@ -149,6 +149,11 @@ int ftrace_make_nop(struct module *mod,
return ret;
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
/* I believe that first is called ftrace_make_nop before this function */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index b463f2aa5a61..45b3f7064fcd 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -12,7 +12,6 @@

#ifdef CONFIG_FUNCTION_TRACER

-#define MCOUNT_ADDR ((unsigned long)(_mcount))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */

#ifndef __ASSEMBLY__
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 2625232bfe52..85de81985e6f 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -61,7 +61,7 @@ static inline void ftrace_dyn_arch_init_insns(void)
/* la v1, _mcount */
v1 = 3;
buf = (u32 *)&insn_la_mcount[0];
- UASM_i_LA(&buf, v1, MCOUNT_ADDR);
+ UASM_i_LA(&buf, v1, (unsigned long)_mcount);

/* jal (ftrace_caller + 8), jump over the first two instruction */
buf = (u32 *)&insn_jal_ftrace_caller;
@@ -200,6 +200,11 @@ int ftrace_make_nop(struct module *mod,
#endif
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
@@ -232,7 +237,7 @@ int __init ftrace_dyn_arch_init(void)
ftrace_dyn_arch_init_insns();

/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
- ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
+ ftrace_modify_code((unsigned long)_mcount, INSN_NOP);

return 0;
}
diff --git a/arch/nds32/include/asm/ftrace.h b/arch/nds32/include/asm/ftrace.h
index 2f96cc96aa35..97263241249d 100644
--- a/arch/nds32/include/asm/ftrace.h
+++ b/arch/nds32/include/asm/ftrace.h
@@ -7,7 +7,6 @@

#define HAVE_FUNCTION_GRAPH_FP_TEST

-#define MCOUNT_ADDR ((unsigned long)(_mcount))
/* mcount call is composed of three instructions:
* sethi + ori + jral
*/
diff --git a/arch/nds32/kernel/ftrace.c b/arch/nds32/kernel/ftrace.c
index fd2a54b8cd57..8f0c34f7bf5b 100644
--- a/arch/nds32/kernel/ftrace.c
+++ b/arch/nds32/kernel/ftrace.c
@@ -203,6 +203,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,

return ftrace_modify_code(pc, call_insn, nop_insn, true);
}
+
+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
#endif /* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
diff --git a/arch/parisc/include/asm/ftrace.h b/arch/parisc/include/asm/ftrace.h
index 958c0aa5dbb2..e0c7cc7958b8 100644
--- a/arch/parisc/include/asm/ftrace.h
+++ b/arch/parisc/include/asm/ftrace.h
@@ -5,7 +5,6 @@
#ifndef __ASSEMBLY__
extern void mcount(void);

-#define MCOUNT_ADDR ((unsigned long)mcount)
#define MCOUNT_INSN_SIZE 4
#define CC_USING_NOP_MCOUNT
extern unsigned long sys_call_table[];
diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
index b6fb30f2e4bf..4c9d8d1e5262 100644
--- a/arch/parisc/kernel/ftrace.c
+++ b/arch/parisc/kernel/ftrace.c
@@ -186,4 +186,9 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
insn, sizeof(insn)-4);
return 0;
}
+
+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)mcount);
+}
#endif
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 3dfb80b86561..bac76b982d2c 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -5,7 +5,6 @@
#include <asm/types.h>

#ifdef CONFIG_FUNCTION_TRACER
-#define MCOUNT_ADDR ((unsigned long)(_mcount))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */

#ifdef __ASSEMBLY__
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index be1ca98fce5c..728a357c51f0 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -472,6 +472,11 @@ int ftrace_make_nop(struct module *mod,
#endif /* CONFIG_MODULES */
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
#ifdef CONFIG_MODULES
#ifdef CONFIG_PPC64
/*
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index c6dcc5291f97..5ca88b80de44 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -33,7 +33,6 @@ struct dyn_arch_ftrace {
* both auipc and jalr at the same time.
*/

-#define MCOUNT_ADDR ((unsigned long)_mcount)
#define JALR_SIGN_MASK (0x00000800)
#define JALR_OFFSET_MASK (0x00000fff)
#define AUIPC_OFFSET_MASK (0xfffff000)
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index b94d8db5ddcc..88fcdbf84ad8 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -88,6 +88,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return __ftrace_modify_call(rec->ip, addr, false);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 68d362f8d6c1..e70717c37f68 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -30,7 +30,6 @@ extern unsigned long ftrace_plt;

struct dyn_arch_ftrace { };

-#define MCOUNT_ADDR ((unsigned long)_mcount)
#define FTRACE_ADDR ((unsigned long)ftrace_caller)

#define KPROBE_ON_FTRACE_NOP 0
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 1bb85f60c0dd..b74e35cc2262 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -110,11 +110,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,

if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
return -EFAULT;
- if (addr == MCOUNT_ADDR) {
- /* Initial code replacement */
- ftrace_generate_orig_insn(&orig);
- ftrace_generate_nop_insn(&new);
- } else if (is_kprobe_on_ftrace(&old)) {
+ if (is_kprobe_on_ftrace(&old)) {
/*
* If we find a breakpoint instruction, a kprobe has been
* placed at the beginning of the function. We write the
@@ -136,6 +132,22 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return 0;
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ struct ftrace_insn orig, new, old;
+
+ if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
+ return -EFAULT;
+ ftrace_generate_orig_insn(&orig);
+ ftrace_generate_nop_insn(&new);
+ /* Verify that the to be replaced code matches what we expect. */
+ if (memcmp(&orig, &old, sizeof(old)))
+ return -EINVAL;
+ s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+
+ return 0;
+}
+
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
struct ftrace_insn orig, new, old;
diff --git a/arch/sh/include/asm/ftrace.h b/arch/sh/include/asm/ftrace.h
index b1c1dc0cc261..5a7890b7a0d2 100644
--- a/arch/sh/include/asm/ftrace.h
+++ b/arch/sh/include/asm/ftrace.h
@@ -10,8 +10,6 @@
#ifndef __ASSEMBLY__
extern void mcount(void);

-#define MCOUNT_ADDR ((unsigned long)(mcount))
-
#ifdef CONFIG_DYNAMIC_FTRACE
#define CALL_ADDR ((long)(ftrace_call))
#define STUB_ADDR ((long)(ftrace_stub))
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
index 1b04270e5460..f7a12102a93d 100644
--- a/arch/sh/kernel/ftrace.c
+++ b/arch/sh/kernel/ftrace.c
@@ -242,6 +242,11 @@ int ftrace_make_nop(struct module *mod,
return ftrace_modify_code(rec->ip, old, new);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)mcount);
+}
+
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char *new, *old;
diff --git a/arch/sparc/include/asm/ftrace.h b/arch/sparc/include/asm/ftrace.h
index d3aa1a524431..a1eecda8976b 100644
--- a/arch/sparc/include/asm/ftrace.h
+++ b/arch/sparc/include/asm/ftrace.h
@@ -3,7 +3,6 @@
#define _ASM_SPARC64_FTRACE

#ifdef CONFIG_MCOUNT
-#define MCOUNT_ADDR ((unsigned long)(_mcount))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */

#ifndef __ASSEMBLY__
diff --git a/arch/sparc/kernel/ftrace.c b/arch/sparc/kernel/ftrace.c
index 684b84ce397f..7a16482fdd29 100644
--- a/arch/sparc/kernel/ftrace.c
+++ b/arch/sparc/kernel/ftrace.c
@@ -63,6 +63,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long ad
return ftrace_modify_code(ip, old, new);
}

+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
+{
+ return ftrace_make_nop(mod, rec, (unsigned long)_mcount);
+}
+
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 287f1f7b2e52..58fe65fc5a63 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -6,7 +6,6 @@
#ifndef CC_USING_FENTRY
# error Compiler does not support fentry?
#endif
-# define MCOUNT_ADDR ((unsigned long)(__fentry__))
#define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */

#ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 024c3053dbba..3cdba006f848 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -149,26 +149,28 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
return 0;
}

-int ftrace_make_nop(struct module *mod,
- struct dyn_ftrace *rec, unsigned long addr)
+/*
+ * On boot up, and when modules are loaded, the __fentry__
+ * is converted to a nop, and will never become __fentry__
+ * again. This code is either running before SMP (on boot up)
+ * or before the code will ever be executed (module load).
+ * We do not want to use the breakpoint version in this case,
+ * just modify the code directly.
+ */
+int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec)
{
unsigned const char *new, *old;
unsigned long ip = rec->ip;

- old = ftrace_call_replace(ip, addr);
+ old = ftrace_call_replace(ip, (unsigned long)__fentry__);
new = ftrace_nop_replace();

- /*
- * On boot up, and when modules are loaded, the MCOUNT_ADDR
- * is converted to a nop, and will never become MCOUNT_ADDR
- * again. This code is either running before SMP (on boot up)
- * or before the code will ever be executed (module load).
- * We do not want to use the breakpoint version in this case,
- * just modify the code directly.
- */
- if (addr == MCOUNT_ADDR)
- return ftrace_modify_code_direct(rec->ip, old, new);
+ return ftrace_modify_code_direct(ip, old, new);
+}

+int ftrace_make_nop(struct module *mod,
+ struct dyn_ftrace *rec, unsigned long addr)
+{
ftrace_expected = NULL;

/* Normal cases use add_brk_on_nop */
diff --git a/arch/xtensa/include/asm/ftrace.h b/arch/xtensa/include/asm/ftrace.h
index 6c6d9a9f185f..3ce2170291cd 100644
--- a/arch/xtensa/include/asm/ftrace.h
+++ b/arch/xtensa/include/asm/ftrace.h
@@ -28,7 +28,6 @@ extern unsigned long return_address(unsigned level);

#ifdef CONFIG_FUNCTION_TRACER

-#define MCOUNT_ADDR ((unsigned long)(_mcount))
#define MCOUNT_INSN_SIZE 3

#ifndef __ASSEMBLY__
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 8a8cb3c401b2..8175ffb671f0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -458,6 +458,7 @@ extern void ftrace_regs_caller(void);
extern void ftrace_call(void);
extern void ftrace_regs_call(void);
extern void mcount_call(void);
+extern int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec);

void ftrace_modify_all_code(int command);

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eca34503f178..62ca6977e570 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2500,7 +2500,7 @@ ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
if (unlikely(ftrace_disabled))
return 0;

- ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+ ret = ftrace_call_init(mod, rec);
if (ret) {
ftrace_bug_type = FTRACE_BUG_INIT;
ftrace_bug(ret, rec);
--
2.23.0.rc1

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