On 09/20/2017 11:31 PM, Konrad Rzeszutek Wilk wrote:
By default when using objcopy we lose the alignment when we copy it from xen-syms - with the result that alignment (on ARM32 for example) can be 1:[Nr] Name Type Addr Off Size ES Flg Lk Inf Al .. [ 6] .livepatch.depend PROGBITS 00000000 000093 000024 00 A 0 0 1 That, combined with wacky offset means it will be loaded in memory with the wrong alignment: (XEN) livepatch.c:425: livepatch: xen_bye_world: Loaded .livepatch.depends at 000a08043 And later we crash as the .livepatch.depends is not aligned to four bytes, while the xen_build_id_check expects the code to be four byte aligned and we get an hypervisor crash (on ARM32): (XEN) CPU0: Unexpected Trap: Data Abort (XEN) ----[ Xen-4.10Hello World arm32 debug=y Not tainted ]---- (XEN) CPU: 0 (XEN) PC: 002400a0 xen_build_id_check+0x8/0xe8 ..snip.. (XEN) Xen call trace: (XEN) [<002400a0>] xen_build_id_check+0x8/0xe8 (PC) (XEN) [<0021a9c0>] livepatch_op+0x768/0x1610 (LR) (XEN) [<0023bbe4>] do_sysctl+0x9c8/0xa9c (XEN) [<002673c4>] do_trap_guest_sync+0x11e0/0x177c (XEN) [<0026b6a0>] entry.o#return_from_trap+0/0x4 (XEN) (XEN) (XEN) **************************************** (XEN) Panic on CPU 0: (XEN) CPU0: Unexpected Trap: Data Abort This fix forces all the test-cases to be built with a .livepatch.depends structure containing the build-id extracted from the hypervisor (except the xen_bye_world test-case). We use the 'mkhex' tool instead of 'xxd' as the end result is an 'unsigned' instead of 'char' type array - which naturally forces the alignment to be of four. Also the 'mkhex' tools allows us to pass the section name as parameter. The end result is much better alignment: [ 7] .livepatch.depend PROGBITS 00000000 000094 000024 00 A 0 0 4 Note that thanks to 'unsigned int .. __note_depends' the symbol becomes global: $ readelf --symbols *.livepatch | grep depen 23: 0000000000000000 36 OBJECT GLOBAL HIDDEN 6 note_depends 49: 0000000000000000 36 OBJECT GLOBAL HIDDEN 17 note_depends 16: 0000000000000000 36 OBJECT GLOBAL HIDDEN 3 note_depends 21: 0000000000000000 36 OBJECT GLOBAL HIDDEN 6 note_depends See patch titled: "livepatch/arm/x86: Rename note_depends symbol from test-cases." which fixes this. Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> --- Cc: Jan Beulich <jbeul...@suse.com> Cc: Andrew Cooper <andrew.coop...@citrix.com> Cc: Ian Jackson <ian.jack...@eu.citrix.com> Cc: Wei Liu <wei.l...@citrix.com>
Acked-by: Ross Lagerwall <ross.lagerw...@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
