Re: [PATCH] kexec: Support purgatories with .text.hot sections

[Baoquan He]

On 03/22/23 at 03:42pm, Ricardo Ribalda wrote:
> Hi Steven
> 
> On Wed, 22 Mar 2023 at 15:34, Steven Rostedt <rostedt@xxxxxxxxxxx> 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) {
> >
> > Shouldn't this be: kbuf->image->start == pi->ehdr->e_shnum) {
> 
> You are absolutely right, I screwed up when I ported the code from my
> test tree to the tree that I use for upstreaming.
> Instead of removing all the printks I wrote code.
> 
> :S
> 
> Will resend the patch

When you resne patch, please fix Philipp's mail adress as
'Philipp Rudo <prudo@xxxxxxxxxx>' if he should know this. He has joined
Redhat.

Thanks
Baoquan