Messages in this thread | | | Date | Thu, 25 Feb 2021 09:44:26 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() |
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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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