Messages in this thread | | | Subject | Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() | From | Li Huafei <> | Date | Wed, 3 Mar 2021 09:25:05 +0800 |
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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
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