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  1. 17 Sep, 2024 2 commits
    • Tiezhu Yang's avatar
      objtool: Handle frame pointer related instructions · da5b2ad1
      Tiezhu Yang authored 
      After commit a0f7085f ("LoongArch: Add RANDOMIZE_KSTACK_OFFSET
support"), there are three new instructions "addi.d $fp, $sp, 32",
"sub.d $sp, $sp, $t0" and "addi.d $sp, $fp, -32" for the secondary
stack in do_syscall(), then there is a objtool warning "return with
modified stack frame" and no handle_syscall() which is the previous
frame of do_syscall() in the call trace when executing the command
"echo l > /proc/sysrq-trigger".

objdump shows something like this:

0000000000000000 <do_syscall>:
   0:   02ff8063        addi.d          $sp, $sp, -32
   4:   29c04076        st.d            $fp, $sp, 16
   8:   29c02077        st.d            $s0, $sp, 8
   c:   29c06061        st.d            $ra, $sp, 24
  10:   02c08076        addi.d          $fp, $sp, 32
  ...
  74:   0011b063        sub.d           $sp, $sp, $t0
  ...
  a8:   4c000181        jirl            $ra, $t0, 0
  ...
  dc:   02ff82c3        addi.d          $sp, $fp, -32
  e0:   28c06061        ld.d            $ra, $sp, 24
  e4:   28c04076        ld.d            $fp, $sp, 16
  e8:   28c02077        ld.d            $s0, $sp, 8
  ec:   02c08063        addi.d          $sp, $sp, 32
  f0:   4c000020        jirl            $zero, $ra, 0

The instruction "sub.d $sp, $sp, $t0" changes the stack bottom and the
new stack size is a random value, in order to find the return address of
do_syscall() which is stored in the original stack frame after executing
"jirl $ra, $t0, 0", it should use fp which points to the original stack
top.

At the beginning, the thought is tended to decode the secondary stack
instruction "sub.d $sp, $sp, $t0" and set it as a label, then check this
label for the two frame pointer instructions to change the cfa base and
cfa offset during the period of secondary stack in update_cfi_state().
This is valid for GCC but invalid for Clang due to there are different
secondary stack instructions for ClangBuiltLinux on LoongArch, something
like this:

0000000000000000 <do_syscall>:
  ...
  88:   00119064        sub.d           $a0, $sp, $a0
  8c:   00150083        or              $sp, $a0, $zero
  ...

Actually, it equals to a single instruction "sub.d $sp, $sp, $a0", but
there is no proper condition to check it as a label like GCC, and so the
beginning thought is not a good way.

Essentially, there are two special frame pointer instructions which are
"addi.d $fp, $sp, imm" and "addi.d $sp, $fp, imm", the first one points
fp to the original stack top and the second one restores the original
stack bottom from fp.

Based on the above analysis, in order to avoid adding an arch-specific
update_cfi_state(), we just add a member "frame_pointer" in the "struct
symbol" as a label to avoid affecting the current normal case, then set
it as true only if there is "addi.d $sp, $fp, imm". The last is to check
this label for the two frame pointer instructions to change the cfa base
and cfa offset in update_cfi_state().

Tested with the following two configs:
(1) CONFIG_RANDOMIZE_KSTACK_OFFSET=y &&
    CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=n
(2) CONFIG_RANDOMIZE_KSTACK_OFFSET=y &&
    CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=y

By the way, there is no effect for x86 with this patch, tested on the
x86 machine with Fedora 40 system.

Cc: stable@vger.kernel.org # 6.9+
Signed-off-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
      da5b2ad1
    • Huacai Chen's avatar
      Merge tag 'irq-core-2024-09-16' into loongarch-next · 987cbafe
      Huacai Chen authored 
      LoongArch architecture changes for 6.12 depend on the irq core
changes about AVEC irqchip to avoid confliction, so merge them
to create a base.
      987cbafe
  3. 15 Sep, 2024 3 commits
    • Linus Torvalds's avatar
      Linux 6.11 · 98f7e32f
      Linus Torvalds authored
      98f7e32f
    • Linus Torvalds's avatar
      Merge tag 'for-linus-6.11' of git://git.kernel.org/pub/scm/virt/kvm/kvm · d42f7708
      Linus Torvalds authored 
      Pull kvm fix from Paolo Bonzini:
 "Do not always honor guest PAT on CPUs that support self-snoop.

  This triggers an issue in the bochsdrm driver, which used ioremap()
  instead of ioremap_wc() to map the video RAM.

  The revert lets video RAM use the WB memory type instead of the slower
  UC memory type"

* tag 'for-linus-6.11' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  Revert "KVM: VMX: Always honor guest PAT on CPUs that support self-snoop"
      d42f7708
    • Paolo Bonzini's avatar
      Revert "KVM: VMX: Always honor guest PAT on CPUs that support self-snoop" · 9d70f3fe
      Paolo Bonzini authored 
      This reverts commit 377b2f35.

This caused a regression with the bochsdrm driver, which used ioremap()
instead of ioremap_wc() to map the video RAM.  After the commit, the
WB memory type is used without the IGNORE_PAT, resulting in the slower
UC memory type.  In fact, UC is slow enough to basically cause guests
to not boot... but only on new processors such as Sapphire Rapids and
Cascade Lake.  Coffee Lake for example works properly, though that might
also be an effect of being on a larger, more NUMA system.

The driver has been fixed but that does not help older guests.  Until we
figure out whether Cascade Lake and newer processors are working as
intended, revert the commit.  Long term we might add a quirk, but the
details depend on whether the processors are working as intended: for
example if they are, the quirk might reference bochs-compatible devices,
e.g. in the name and documentation, so that userspace can disable the
quirk by default and only leave it enabled if such a device is being
exposed to the guest.

If instead this is actually a bug in CLX+, then the actions we need to
take are different and depend on the actual cause of the bug.
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      9d70f3fe
  5. 14 Sep, 2024 4 commits
  7. 13 Sep, 2024 11 commits
  9. 12 Sep, 2024 20 commits
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