On Tue, Mar 21, 2023 at 12:49:08PM +0100, Ricardo Ribalda 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
>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> To: Eric Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx>
> Cc: kexec@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> kernel/kexec_file.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index f1a0e4e3fb5c..b1a25d97d5e2 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -904,7 +904,8 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
> 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_shnum) {
Shouldn't this be: kbuf->image->start == pi->ehdr->e_shnum) {
?
As you want to only do this update when it's not equal to the initial value.
If this did work, then you may want to make sure that was the initial value.
Also, please add a comment about why you are doing this check.
Thanks!
-- Steve
> kbuf->image->start -= sechdrs[i].sh_addr;
> kbuf->image->start += kbuf->mem + offset;
> }
>
> ---
> base-commit: 17214b70a159c6547df9ae204a6275d983146f6b
> change-id: 20230321-kexec_clang16-4510c23d129c
>
> Best regards,
> --
> Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
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