Hi Ricardo, On Wed, 22 Mar 2023 20:09:21 +0100 Ricardo Ribalda <ribalda@xxxxxxxxxxxx> wrote: > Clang16 links the purgatory text in two sections: > > [ 1] .text PROGBITS 0000000000000000 00000040 > 00000000000011a1 0000000000000000 AX 0 0 16 > [ 2] .rela.text RELA 0000000000000000 00003498 > 0000000000000648 0000000000000018 I 24 1 8 > ... > [17] .text.hot. PROGBITS 0000000000000000 00003220 > 000000000000020b 0000000000000000 AX 0 0 1 > [18] .rela.text.hot. RELA 0000000000000000 00004428 > 0000000000000078 0000000000000018 I 24 17 8 > > And both of them have their range [sh_addr ... sh_addr+sh_size] on the > area pointed by `e_entry`. > > This causes that image->start is calculated twice, once for .text and > another time for .text.hot. The second calculation leaves image->start > in a random location. > > Because of this, the system crashes inmediatly after: > > kexec_core: Starting new kernel Great analysis! > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> > --- > kexec: Fix kexec_file_load for llvm16 > > When upreving llvm I realised that kexec stopped working on my test > platform. This patch fixes it. > > To: Eric Biederman <ebiederm@xxxxxxxxxxxx> > Cc: Baoquan He <bhe@xxxxxxxxxx> > Cc: Philipp Rudo <prudo@xxxxxxxxxx> > Cc: kexec@xxxxxxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > --- > Changes in v3: > - Fix initial value. Thanks Ross! > - Link to v2: https://lore.kernel.org/r/20230321-kexec_clang16-v2-0-d10e5d517869@xxxxxxxxxxxx > > Changes in v2: > - Fix if condition. Thanks Steven!. > - Update Philipp email. Thanks Baoquan. > - Link to v1: https://lore.kernel.org/r/20230321-kexec_clang16-v1-0-a768fc2c7c4d@xxxxxxxxxxxx > --- > kernel/kexec_file.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index f1a0e4e3fb5c..25a37d8f113a 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -901,10 +901,21 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, > } > > offset = ALIGN(offset, align); > + > + /* > + * Check if the segment contains the entry point, if so, > + * calculate the value of image->start based on it. > + * If the compiler has produced more than one .text sections > + * (Eg: .text.hot), they are generally after the main .text > + * section, and they shall not be used to calculate > + * image->start. So do not re-calculate image->start if it > + * is not set to the initial value. > + */ > if (sechdrs[i].sh_flags & SHF_EXECINSTR && > pi->ehdr->e_entry >= sechdrs[i].sh_addr && > pi->ehdr->e_entry < (sechdrs[i].sh_addr > - + sechdrs[i].sh_size)) { > + + sechdrs[i].sh_size) && > + kbuf->image->start == pi->ehdr->e_entry) { I'm not entirely sure if this is the solution to go with. As you state in the comment above this solution assumes that the .text section comes before any other .text.* section. But this assumption isn't much stronger than the assumption that there is only a single .text section, which is used nowadays. The best solution I can come up with right now is to introduce a linker script for the purgatory that simply merges the .text sections into one. Similar to what I did for s390 in arch/s390/purgatory/purgatory.lds.S (although for a different reason). But that would require every architecture to get one. An alternative would be to find a way to get rid of the -r option on the LD_FLAGS, which IIRC is the reason why both section overlap in the first place. Thanks Philipp > kbuf->image->start -= sechdrs[i].sh_addr; > kbuf->image->start += kbuf->mem + offset; > } > > --- > base-commit: 17214b70a159c6547df9ae204a6275d983146f6b > change-id: 20230321-kexec_clang16-4510c23d129c > > Best regards, _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
