On 11/15/23 08:58, Patrick Venture wrote:
>
>
> On Wed, Nov 15, 2023 at 2:35 AM Peter Maydell <peter.maydell@linaro.org
> <mailto:peter.maydell@linaro.org>> wrote:
>
> On Tue, 14 Nov 2023 at 20:55, Patrick Venture <venture@google.com
> <mailto:venture@google.com>> wrote:
> > Avoids unaligned pointer issues.
> >
>
> It would be nice to be more specific in the commit message here, by
> describing what kind of guest behaviour or machine config runs into this
> problem, and whether this happens in a situation users are likely to
> run into. If the latter, we should consider tagging the commit
> with "Cc: qemu-stable@nongnu.org <mailto:qemu-stable@nongnu.org>" to have it
> backported to the
> stable release branches.
>
>
> Thanks! I'll update the commit message with v2. We were seeing this in our
> infrastructure with unaligned accesses using the pointer dereference as there are no
> guarantees on alignment of the incoming values.
Which host cpu, for reference? There aren't many that generate unaligned traps these days...
Here's the sanitizer log/qemu log, the host-cpu was an amd64.
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.07H:EBX.erms [bit 9]
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10]
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17]
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.07H:EBX.erms [bit 9]
qemu-kvm-system-x86_64: warning: host doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10]
third_party/qemu/softmmu/memory.c:1341:16: runtime error: load of misaligned address 0x52500020b10d for type 'uint32_t' (aka 'unsigned int'), which requires 4 byte alignment
0x52500020b10d: note: pointer points here
ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
^
#0 0x55b34f8ef9d8 in memory_region_ram_device_read third_party/qemu/softmmu/memory.c:1341:16
#1 0x55b34f8ee8a8 in memory_region_read_accessor third_party/qemu/softmmu/memory.c:441:11
#2 0x55b34f8e06db in access_with_adjusted_size third_party/qemu/softmmu/memory.c:569:18
#3 0x55b34f8dfcb4 in memory_region_dispatch_read1 third_party/qemu/softmmu/memory.c
#4 0x55b34f8dfcb4 in memory_region_dispatch_read third_party/qemu/softmmu/memory.c:1476:9
#5 0x55b34f8fa8b0 in flatview_read_continue third_party/qemu/softmmu/physmem.c:2744:23
#6 0x55b34f8fb0db in flatview_read third_party/qemu/softmmu/physmem.c:2786:12
#7 0x55b34f8faefa in address_space_read_full third_party/qemu/softmmu/physmem.c:2799:18
#8 0x55b34f8fb5b4 in address_space_rw third_party/qemu/softmmu/physmem.c:2827:16
#9 0x55b34f71eab5 in kvm_cpu_exec third_party/qemu/accel/kvm/kvm-all.c:3062:13
#10 0x55b34f7172e3 in kvm_vcpu_thread_fn third_party/qemu/accel/kvm/kvm-accel-ops.c:51:17
#11 0x55b350467044 in qemu_thread_start third_party/qemu/util/qemu-thread-posix.c:541:9
#12 0x55b34f6dba10 in asan_thread_start(void*) third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:234:28
#13 0x7f5e1c81a7d8 in start_thread (/usr/grte/v5/lib64/libpthread.so.0+0xb7d8) (BuildId: 3ccc1600b9140e48da03ed16e0210354)
#14 0x7f5e1c77169e in clone (/usr/grte/v5/lib64/libc.so.6+0x13969e) (BuildId: 280088eab084c30a3992a9bce5c35b44)
SUMMARY: UndefinedBehaviorSanitizer: misaligned-pointer-use third_party/qemu/softmmu/memory.c:1341:16 in
r~