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Peter Zijlstra 7117f16bf4 objtool: Fix ORC vs alternatives 
Jann reported that (for instance) entry_64.o:general_protection has
very odd ORC data:

  0000000000000f40 <general_protection>:
  #######sp:sp+8 bp:(und) type:iret end:0
    f40:       90                      nop
  #######sp:(und) bp:(und) type:call end:0
    f41:       90                      nop
    f42:       90                      nop
  #######sp:sp+8 bp:(und) type:iret end:0
    f43:       e8 a8 01 00 00          callq  10f0 <error_entry>
  #######sp:sp+0 bp:(und) type:regs end:0
    f48:       f6 84 24 88 00 00 00    testb  $0x3,0x88(%rsp)
    f4f:       03
    f50:       74 00                   je     f52 <general_protection+0x12>
    f52:       48 89 e7                mov    %rsp,%rdi
    f55:       48 8b 74 24 78          mov    0x78(%rsp),%rsi
    f5a:       48 c7 44 24 78 ff ff    movq   $0xffffffffffffffff,0x78(%rsp)
    f61:       ff ff
    f63:       e8 00 00 00 00          callq  f68 <general_protection+0x28>
    f68:       e9 73 02 00 00          jmpq   11e0 <error_exit>
  #######sp:(und) bp:(und) type:call end:0
    f6d:       0f 1f 00                nopl   (%rax)

Note the entry at 0xf41. Josh found this was the result of commit:

  764eef4b10 ("objtool: Rewrite alt->skip_orig")

Due to the early return in validate_branch() we no longer set
insn->cfi of the original instruction stream (the NOPs at 0xf41 and
0xf42) and we'll end up with the above weirdness.

In other discussions we realized alternatives should be ORC invariant;
that is, due to there being only a single ORC table, it must be valid
for all alternatives. The easiest way to ensure this is to not allow
any stack modifications in alternatives.

When we enforce this latter observation, we get the property that the
whole alternative must have the same CFI, which we can employ to fix
the former report.

Fixes: 764eef4b10 ("objtool: Rewrite alt->skip_orig")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191659.499074346@infradead.org
2020-04-30 20:14:31 +02:00
..
accounting SPDX patches for 5.7-rc1. 2020-04-03 13:12:26 -07:00
arch objtool: Remove SAVE/RESTORE hints 2020-04-22 10:53:50 +02:00
bootconfig New tracing features: 2020-04-05 10:36:18 -07:00
bpf tools, bpftool: Fix struct_ops command invalid pointer free 2020-04-14 21:33:53 +02:00
build tools/build: tweak unused value workaround 2020-04-21 11:11:55 -07:00
cgroup .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
debugging
edid tools/edid: Move EDID data sets from Documentation/ 2020-02-19 04:10:32 -07:00
firewire
firmware
gpio This is the bulk of GPIO development for the v5.7 kernel cycle. 2020-04-04 10:27:00 -07:00
hv Tools: hv: Reopen the devices if read() or write() returns errors 2020-01-26 22:10:10 -05:00
iio .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
include tools headers: Synchronize linux/bits.h with the kernel sources 2020-04-14 11:40:05 -03:00
io_uring
kvm/kvm_stat tools/kvm_stat: add command line switch '-c' to log in csv format 2020-03-23 15:44:21 -04:00
laptop change email address for Pali Rohár 2020-04-10 15:36:22 -07:00
leds .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
lib libbpf: Fix type of old_fd in bpf_xdp_set_link_opts 2020-04-15 13:26:08 +02:00
memory-model .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
nfsd
objtool objtool: Fix ORC vs alternatives 2020-04-30 20:14:31 +02:00
pci tools: PCI: Add 'e' to clear IRQ 2020-04-02 17:57:10 +01:00
pcmcia .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
perf tools headers: Synchronize linux/bits.h with the kernel sources 2020-04-14 11:40:05 -03:00
power SPDX patches for 5.7-rc1. 2020-04-03 13:12:26 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-03-25 18:58:11 -07:00
spi SPDX patches for 5.7-rc1. 2020-04-03 13:12:26 -07:00
testing Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-04-16 14:52:29 -07:00
thermal/tmon - Convert tsens configuration DT binding to yaml (Rajeshwari) 2020-04-07 20:00:16 -07:00
time
usb .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
virtio tools/virtio: make asm/barrier.h self contained 2020-04-17 06:05:29 -04:00
vm tools/vm: fix cross-compile build 2020-04-21 11:11:56 -07:00
wmi
Makefile tools: bootconfig: Add bootconfig command 2020-01-13 13:19:39 -05:00