* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
[not found] <20210225140747.10818-1-lihuafei1@huawei.com>
@ 2021-02-25 14:44 ` Steven Rostedt
2021-02-25 16:01 ` Will Deacon
0 siblings, 1 reply; 7+ messages in thread
From: Steven Rostedt @ 2021-02-25 14:44 UTC (permalink / raw)
To: Li Huafei
Cc: Catalin Marinas, linux-kernel, christophe.leroy, zhangjinhao2,
yangjihong1, gregory.herrero, xukuohai, Will Deacon,
linux-arm-kernel
This requires an acked-by from one of the ARM64 maintainers.
-- Steve
On Thu, 25 Feb 2021 22:07:47 +0800
Li Huafei <lihuafei1@huawei.com> wrote:
> When cross-compiling the kernel, the endian of the target machine and
> the local machine may not match, at this time the recordmcount tool
> needs byte reversal when processing elf's variables to get the correct
> value. w* callback function is used to solve this problem, w is used for
> 4-byte variable processing, while w8 is used for 8-byte.
>
> arm64_is_fake_mcount() is used to filter '_mcount' relocations that are
> not used by ftrace. In arm64_is_fake_mcount(), rp->info is 8 bytes in
> size, but w is used. This causes arm64_is_fake_mcount() to get the wrong
> type of relocation when we cross-compile the arm64_be kernel image on an
> x86_le machine, and all valid '_mcount' is filtered out. The
> recordmcount tool does not collect any mcount function call locations.
> At kernel startup, the following ftrace log is seen:
>
> ftrace: No functions to be traced?
>
> and thus ftrace cannot be used.
>
> Using w8 to get the value of rp->r_info will fix the problem.
>
> Fixes: ea0eada45632 ("recordmcount: only record relocation of type
> R_AARCH64_CALL26 on arm64")
> Signed-off-by: Li Huafei <lihuafei1@huawei.com>
> ---
> scripts/recordmcount.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> index b9c2ee7ab43f..cce12e1971d8 100644
> --- a/scripts/recordmcount.c
> +++ b/scripts/recordmcount.c
> @@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
>
> static int arm64_is_fake_mcount(Elf64_Rel const *rp)
> {
> - return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
> + return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
> }
>
> /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
_______________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-02-25 14:44 ` [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() Steven Rostedt
@ 2021-02-25 16:01 ` Will Deacon
2021-02-25 16:08 ` Steven Rostedt
2021-03-02 22:30 ` Steven Rostedt
0 siblings, 2 replies; 7+ messages in thread
From: Will Deacon @ 2021-02-25 16:01 UTC (permalink / raw)
To: Steven Rostedt
Cc: catalin.marinas, linux-kernel, christophe.leroy, zhangjinhao2,
yangjihong1, Li Huafei, gregory.herrero, xukuohai,
linux-arm-kernel
On Thu, Feb 25, 2021 at 09:44:26AM -0500, Steven Rostedt wrote:
> This requires an acked-by from one of the ARM64 maintainers.
>
> -- Steve
>
>
> On Thu, 25 Feb 2021 22:07:47 +0800
> Li Huafei <lihuafei1@huawei.com> wrote:
>
> > When cross-compiling the kernel, the endian of the target machine and
> > the local machine may not match, at this time the recordmcount tool
> > needs byte reversal when processing elf's variables to get the correct
> > value. w* callback function is used to solve this problem, w is used for
> > 4-byte variable processing, while w8 is used for 8-byte.
> >
> > arm64_is_fake_mcount() is used to filter '_mcount' relocations that are
> > not used by ftrace. In arm64_is_fake_mcount(), rp->info is 8 bytes in
> > size, but w is used. This causes arm64_is_fake_mcount() to get the wrong
> > type of relocation when we cross-compile the arm64_be kernel image on an
> > x86_le machine, and all valid '_mcount' is filtered out. The
> > recordmcount tool does not collect any mcount function call locations.
> > At kernel startup, the following ftrace log is seen:
> >
> > ftrace: No functions to be traced?
> >
> > and thus ftrace cannot be used.
> >
> > Using w8 to get the value of rp->r_info will fix the problem.
> >
> > Fixes: ea0eada45632 ("recordmcount: only record relocation of type
> > R_AARCH64_CALL26 on arm64")
> > Signed-off-by: Li Huafei <lihuafei1@huawei.com>
> > ---
> > scripts/recordmcount.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> > index b9c2ee7ab43f..cce12e1971d8 100644
> > --- a/scripts/recordmcount.c
> > +++ b/scripts/recordmcount.c
> > @@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
> >
> > static int arm64_is_fake_mcount(Elf64_Rel const *rp)
> > {
> > - return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
> > + return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
Acked-by: Will Deacon <will@kernel.org>
But you know you could avoid these sorts of problems by moving to little
endian along with everybody else? ;)
Will
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-02-25 16:01 ` Will Deacon
@ 2021-02-25 16:08 ` Steven Rostedt
2021-03-02 22:30 ` Steven Rostedt
1 sibling, 0 replies; 7+ messages in thread
From: Steven Rostedt @ 2021-02-25 16:08 UTC (permalink / raw)
To: Will Deacon
Cc: catalin.marinas, linux-kernel, christophe.leroy, zhangjinhao2,
yangjihong1, Li Huafei, gregory.herrero, xukuohai,
linux-arm-kernel
On Thu, 25 Feb 2021 16:01:17 +0000
Will Deacon <will@kernel.org> wrote:
> Acked-by: Will Deacon <will@kernel.org>
Thanks!
>
> But you know you could avoid these sorts of problems by moving to little
> endian along with everybody else? ;)
But then how do we find these bug?
-- Steve
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-02-25 16:01 ` Will Deacon
2021-02-25 16:08 ` Steven Rostedt
@ 2021-03-02 22:30 ` Steven Rostedt
2021-03-02 22:33 ` Steven Rostedt
2021-03-03 1:25 ` Li Huafei
1 sibling, 2 replies; 7+ messages in thread
From: Steven Rostedt @ 2021-03-02 22:30 UTC (permalink / raw)
To: Will Deacon
Cc: Li Huafei, gregory.herrero, catalin.marinas, christophe.leroy,
linux-kernel, zhangjinhao2, yangjihong1, xukuohai,
linux-arm-kernel, Chen Jun
On Thu, 25 Feb 2021 16:01:17 +0000
Will Deacon <will@kernel.org> wrote:
> On Thu, Feb 25, 2021 at 09:44:26AM -0500, Steven Rostedt wrote:
> > This requires an acked-by from one of the ARM64 maintainers.
> >
> > -- Steve
> >
> >
> > On Thu, 25 Feb 2021 22:07:47 +0800
> > Li Huafei <lihuafei1@huawei.com> wrote:
> >
> > > When cross-compiling the kernel, the endian of the target machine and
> > > the local machine may not match, at this time the recordmcount tool
> > > needs byte reversal when processing elf's variables to get the correct
> > > value. w* callback function is used to solve this problem, w is used for
> > > 4-byte variable processing, while w8 is used for 8-byte.
> > >
> > > arm64_is_fake_mcount() is used to filter '_mcount' relocations that are
> > > not used by ftrace. In arm64_is_fake_mcount(), rp->info is 8 bytes in
> > > size, but w is used. This causes arm64_is_fake_mcount() to get the wrong
> > > type of relocation when we cross-compile the arm64_be kernel image on an
> > > x86_le machine, and all valid '_mcount' is filtered out. The
> > > recordmcount tool does not collect any mcount function call locations.
> > > At kernel startup, the following ftrace log is seen:
> > >
> > > ftrace: No functions to be traced?
> > >
> > > and thus ftrace cannot be used.
> > >
> > > Using w8 to get the value of rp->r_info will fix the problem.
> > >
> > > Fixes: ea0eada45632 ("recordmcount: only record relocation of type
> > > R_AARCH64_CALL26 on arm64")
> > > Signed-off-by: Li Huafei <lihuafei1@huawei.com>
> > > ---
> > > scripts/recordmcount.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> > > index b9c2ee7ab43f..cce12e1971d8 100644
> > > --- a/scripts/recordmcount.c
> > > +++ b/scripts/recordmcount.c
> > > @@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
> > >
> > > static int arm64_is_fake_mcount(Elf64_Rel const *rp)
> > > {
> > > - return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
> > > + return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
>
> Acked-by: Will Deacon <will@kernel.org>
>
> But you know you could avoid these sorts of problems by moving to little
> endian along with everybody else? ;)
>
I just realized that I received this patch twice, and thought it was the
same patch! Chen was three days ahead of you, so he get's the credit ;-)
https://lore.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com
-- Steve
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-03-02 22:30 ` Steven Rostedt
@ 2021-03-02 22:33 ` Steven Rostedt
2021-03-03 13:12 ` Will Deacon
2021-03-03 1:25 ` Li Huafei
1 sibling, 1 reply; 7+ messages in thread
From: Steven Rostedt @ 2021-03-02 22:33 UTC (permalink / raw)
To: Will Deacon
Cc: Li Huafei, gregory.herrero, catalin.marinas, christophe.leroy,
linux-kernel, zhangjinhao2, yangjihong1, xukuohai,
linux-arm-kernel, Chen Jun
On Tue, 2 Mar 2021 17:30:58 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> I just realized that I received this patch twice, and thought it was the
> same patch! Chen was three days ahead of you, so he get's the credit ;-)
>
> https://lore.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com
I'm applying this patch (same one here but came earlier).
Will, you still OK with your acked-by on it?
-- Steve
From 999340d51174ce4141dd723105d4cef872b13ee9 Mon Sep 17 00:00:00 2001
From: Chen Jun <chenjun102@huawei.com>
Date: Mon, 22 Feb 2021 13:58:40 +0000
Subject: [PATCH] ftrace: Have recordmcount use w8 to read relp->r_info in
arm64_is_fake_mcount
On little endian system, Use aarch64_be(gcc v7.3) downloaded from
linaro.org to build image with CONFIG_CPU_BIG_ENDIAN = y,
CONFIG_FTRACE = y, CONFIG_DYNAMIC_FTRACE = y.
gcc will create symbols of _mcount but recordmcount can not create
mcount_loc for *.o.
aarch64_be-linux-gnu-objdump -r fs/namei.o | grep mcount
00000000000000d0 R_AARCH64_CALL26 _mcount
...
0000000000007190 R_AARCH64_CALL26 _mcount
The reason is than funciton arm64_is_fake_mcount can not work correctly.
A symbol of _mcount in *.o compiled with big endian compiler likes:
00 00 00 2d 00 00 01 1b
w(rp->r_info) will return 0x2d instead of 0x011b. Because w() takes
uint32_t as parameter, which truncates rp->r_info.
Use w8() instead w() to read relp->r_info
Link: https://lkml.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com
Fixes: ea0eada45632 ("recordmcount: only record relocation of type R_AARCH64_CALL26 on arm64.")
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
scripts/recordmcount.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index b9c2ee7ab43f..cce12e1971d8 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
static int arm64_is_fake_mcount(Elf64_Rel const *rp)
{
- return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
+ return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
}
/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
--
2.25.4
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-03-02 22:30 ` Steven Rostedt
2021-03-02 22:33 ` Steven Rostedt
@ 2021-03-03 1:25 ` Li Huafei
1 sibling, 0 replies; 7+ messages in thread
From: Li Huafei @ 2021-03-03 1:25 UTC (permalink / raw)
To: Steven Rostedt
Cc: will, gregory.herrero, catalin.marinas, christophe.leroy,
linux-kernel, Zhangjinhao, yangjihong1, linux-arm-kernel,
chenjun102
On 2021/3/3 6:30, Steven Rostedt wrote:
> On Thu, 25 Feb 2021 16:01:17 +0000
> Will Deacon <will@kernel.org> wrote:
>
>> On Thu, Feb 25, 2021 at 09:44:26AM -0500, Steven Rostedt wrote:
>>> This requires an acked-by from one of the ARM64 maintainers.
>>>
>>> -- Steve
>>>
>>>
>>> On Thu, 25 Feb 2021 22:07:47 +0800
>>> Li Huafei <lihuafei1@huawei.com> wrote:
>>>
>>>> When cross-compiling the kernel, the endian of the target machine and
>>>> the local machine may not match, at this time the recordmcount tool
>>>> needs byte reversal when processing elf's variables to get the correct
>>>> value. w* callback function is used to solve this problem, w is used for
>>>> 4-byte variable processing, while w8 is used for 8-byte.
>>>>
>>>> arm64_is_fake_mcount() is used to filter '_mcount' relocations that are
>>>> not used by ftrace. In arm64_is_fake_mcount(), rp->info is 8 bytes in
>>>> size, but w is used. This causes arm64_is_fake_mcount() to get the wrong
>>>> type of relocation when we cross-compile the arm64_be kernel image on an
>>>> x86_le machine, and all valid '_mcount' is filtered out. The
>>>> recordmcount tool does not collect any mcount function call locations.
>>>> At kernel startup, the following ftrace log is seen:
>>>>
>>>> ftrace: No functions to be traced?
>>>>
>>>> and thus ftrace cannot be used.
>>>>
>>>> Using w8 to get the value of rp->r_info will fix the problem.
>>>>
>>>> Fixes: ea0eada45632 ("recordmcount: only record relocation of type
>>>> R_AARCH64_CALL26 on arm64")
>>>> Signed-off-by: Li Huafei <lihuafei1@huawei.com>
>>>> ---
>>>> scripts/recordmcount.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
>>>> index b9c2ee7ab43f..cce12e1971d8 100644
>>>> --- a/scripts/recordmcount.c
>>>> +++ b/scripts/recordmcount.c
>>>> @@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
>>>>
>>>> static int arm64_is_fake_mcount(Elf64_Rel const *rp)
>>>> {
>>>> - return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
>>>> + return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
>>
>> Acked-by: Will Deacon <will@kernel.org>
>>
>> But you know you could avoid these sorts of problems by moving to little
>> endian along with everybody else? ;)
>>
>
> I just realized that I received this patch twice, and thought it was the
> same patch! Chen was three days ahead of you, so he get's the credit ;-)
>
> https://lore.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com
>
> -- Steve
> .
>
That's fine, thanks Steve and Will!
Huafei
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount()
2021-03-02 22:33 ` Steven Rostedt
@ 2021-03-03 13:12 ` Will Deacon
0 siblings, 0 replies; 7+ messages in thread
From: Will Deacon @ 2021-03-03 13:12 UTC (permalink / raw)
To: Steven Rostedt
Cc: Li Huafei, gregory.herrero, catalin.marinas, christophe.leroy,
linux-kernel, zhangjinhao2, yangjihong1, xukuohai,
linux-arm-kernel, Chen Jun
On Tue, Mar 02, 2021 at 05:33:35PM -0500, Steven Rostedt wrote:
> On Tue, 2 Mar 2021 17:30:58 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > I just realized that I received this patch twice, and thought it was the
> > same patch! Chen was three days ahead of you, so he get's the credit ;-)
> >
> > https://lore.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com
>
> I'm applying this patch (same one here but came earlier).
>
> Will, you still OK with your acked-by on it?
Absolutely!
Will
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 7+ messages in thread
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2021-02-25 14:44 ` [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() Steven Rostedt
2021-02-25 16:01 ` Will Deacon
2021-02-25 16:08 ` Steven Rostedt
2021-03-02 22:30 ` Steven Rostedt
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2021-03-03 1:25 ` Li Huafei
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