| Message ID | 20170920223148.13137-2-konrad.wilk@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/20/2017 11:31 PM, Konrad Rzeszutek Wilk wrote: > If the livepatch has only .rodata sections then it is OK to also > apply/revert/apply the livepatch without having to worry about the > unforseen consequences. > > See commit 98b728a7b235c67e210f67f789db5d9eb38ca00c > "livepatch: Disallow applying after an revert" for details. > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > --- > Cc: Ross Lagerwall <ross.lagerwall@citrix.com> > The patch looks OK, but what is the use case for a live patch with only .rodata? Regards,
On Thu, Oct 05, 2017 at 02:47:30PM +0100, Ross Lagerwall wrote: > On 09/20/2017 11:31 PM, Konrad Rzeszutek Wilk wrote: > > If the livepatch has only .rodata sections then it is OK to also > > apply/revert/apply the livepatch without having to worry about the > > unforseen consequences. > > > > See commit 98b728a7b235c67e210f67f789db5d9eb38ca00c > > "livepatch: Disallow applying after an revert" for details. > > > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > > --- > > Cc: Ross Lagerwall <ross.lagerwall@citrix.com> > > > > The patch looks OK, but what is the use case for a live patch with only > .rodata? A NOP one. This hasn't been an issue in the past, but further patches change the .livepatch_funcs from RW to RO (to be in line with what livepatch-build-tools.git do) - and then the xen_nop testcase does not work anymore. > > Regards, > -- > Ross Lagerwall > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > https://lists.xen.org/xen-devel
On 10/05/2017 02:51 PM, Konrad Rzeszutek Wilk wrote: > On Thu, Oct 05, 2017 at 02:47:30PM +0100, Ross Lagerwall wrote: >> On 09/20/2017 11:31 PM, Konrad Rzeszutek Wilk wrote: >>> If the livepatch has only .rodata sections then it is OK to also >>> apply/revert/apply the livepatch without having to worry about the >>> unforseen consequences. >>> >>> See commit 98b728a7b235c67e210f67f789db5d9eb38ca00c >>> "livepatch: Disallow applying after an revert" for details. >>> >>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> >>> --- >>> Cc: Ross Lagerwall <ross.lagerwall@citrix.com> >>> >> >> The patch looks OK, but what is the use case for a live patch with only >> .rodata? > > A NOP one. This hasn't been an issue in the past, but further patches > change the .livepatch_funcs from RW to RO (to be in line with what > livepatch-build-tools.git do) - and then the xen_nop testcase does not > work anymore. > Thanks, that makes sense. Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c index 66167a5573..b0dcd415ba 100644 --- a/xen/common/livepatch.c +++ b/xen/common/livepatch.c @@ -417,9 +417,12 @@ static int move_payload(struct payload *payload, struct livepatch_elf *elf) } } - /* Only one RW section with non-zero size: .livepatch.funcs */ - if ( rw_buf_cnt == 1 && - !strcmp(elf->sec[rw_buf_sec].name, ELF_LIVEPATCH_FUNC) ) + /* + * Only one RW section with non-zero size: .livepatch.funcs, + * or only RO sections. + */ + if ( !rw_buf_cnt || (rw_buf_cnt == 1 && + !strcmp(elf->sec[rw_buf_sec].name, ELF_LIVEPATCH_FUNC)) ) payload->safe_to_reapply = true; out: xfree(offset);
If the livepatch has only .rodata sections then it is OK to also apply/revert/apply the livepatch without having to worry about the unforseen consequences. See commit 98b728a7b235c67e210f67f789db5d9eb38ca00c "livepatch: Disallow applying after an revert" for details. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- Cc: Ross Lagerwall <ross.lagerwall@citrix.com> v3: First posting. --- xen/common/livepatch.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)