Messages in this thread Patch in this message | | | Date | Tue, 2 Mar 2021 17:30:58 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() |
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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
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