On Wed, Mar 22, 2023 at 10:34:46AM -0400, Steven Rostedt wrote:
> 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) {
I think we should also be comparing against the initial value (set ~20 lines
above) of pi->ehdr->e_entry, not pi->ehdr->e_shnum.
This patch works correctly for me:
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f7a4fd4d243f4..967826a42cdd7 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -913,7 +913,8 @@ 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_entry) {
kbuf->image->start -= sechdrs[i].sh_addr;
kbuf->image->start += kbuf->mem + offset;
}
Great find. With those 2 quick changes, you can add:
Reviewed-by: Ross Zwisler <zwisler@xxxxxxxxxx>
> 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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