> On Feb 12, 2020, at 3:55 AM, Joerg Roedel <joro at 8bytes.org> wrote: > > ?On Tue, Feb 11, 2020 at 02:41:25PM -0800, Andy Lutomirski wrote: >>> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro at 8bytes.org> wrote: >>> >>> From: Joerg Roedel <jroedel at suse.de> >>> >>> With SEV-ES, exception handling is needed very early, even before the >>> kernel has cleared the bss segment. In order to prevent clearing the >>> currently used IDT, move the IDT to the data segment. >> >> Ugh. At the very least this needs a comment in the code. > > Yes, right, added a comment for that. > >> I had a patch to fix the kernel ELF loader to clear BSS, which would >> fix this problem once and for all, but it didn't work due to the messy >> way that the decompressor handles memory. I never got around to >> fixing this, sadly. > > Aren't there other ways of booting (Xen-PV?) which don't use the kernel > ELF loader?Dunno. I would hope the any sane loader would clear BSS before executing anything. This isn?t currently the case, though. Oh well.> > Regards, > > Joerg
On 12.02.20 17:23, Andy Lutomirski wrote:> > >> On Feb 12, 2020, at 3:55 AM, Joerg Roedel <joro at 8bytes.org> wrote: >> >> ?On Tue, Feb 11, 2020 at 02:41:25PM -0800, Andy Lutomirski wrote: >>>> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro at 8bytes.org> wrote: >>>> >>>> From: Joerg Roedel <jroedel at suse.de> >>>> >>>> With SEV-ES, exception handling is needed very early, even before the >>>> kernel has cleared the bss segment. In order to prevent clearing the >>>> currently used IDT, move the IDT to the data segment. >>> >>> Ugh. At the very least this needs a comment in the code. >> >> Yes, right, added a comment for that. >> >>> I had a patch to fix the kernel ELF loader to clear BSS, which would >>> fix this problem once and for all, but it didn't work due to the messy >>> way that the decompressor handles memory. I never got around to >>> fixing this, sadly. >> >> Aren't there other ways of booting (Xen-PV?) which don't use the kernel >> ELF loader? > > Dunno. I would hope the any sane loader would clear BSS before executing anything. This isn?t currently the case, though. Oh well.Xen-PV is clearing BSS as the very first action. Juergen
Hi J?rgen, On Wed, Feb 12, 2020 at 05:28:21PM +0100, J?rgen Gro? wrote:> Xen-PV is clearing BSS as the very first action.In the kernel image? Or in the ELF loader before jumping to the kernel image? Regards, Joerg