From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Arnd Bergmann" <arnd@arndb.de>, "Jann Horn" <jannh@google.com>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx_vmenter()
Date: Mon, 15 Jul 2019 07:37:04 -0500 [thread overview]
Message-ID: <20190715123704.oke4pd4wguj5a7i3@treble> (raw)
In-Reply-To: <0b37031b-1043-8274-a086-2b5d0b02b5ef@redhat.com>
On Mon, Jul 15, 2019 at 11:04:03AM +0200, Paolo Bonzini wrote:
> On 15/07/19 02:36, Josh Poimboeuf wrote:
> > With CONFIG_FRAME_POINTER, vmx_vmenter() needs to do frame pointer setup
> > before calling kvm_spurious_fault().
> >
> > Fixes the following warning:
> >
> > arch/x86/kvm/vmx/vmenter.o: warning: objtool: vmx_vmenter()+0x14: call without frame pointer save/setup
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
>
> This is not enough, because the RSP value must match what is computed at
> this place:
>
> /* Adjust RSP to account for the CALL to vmx_vmenter(). */
> lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
> call vmx_update_host_rsp
Ah, that is surprising :-)
And then there's this, which overwrites the frame pointer anyway:
mov VCPU_RBP(%_ASM_AX), %_ASM_BP
Would it make sense to remove the call to vmx_vmenter() altogether, and
just either embed it in __vmx_vcpu_run(), or jmp back and forth to it
from __vmx_vcpu_run()?
Then you could get rid of the RSP adjustment hack, and the
vmx_update_host_rsp() function altogether.
> Is this important since kvm_spurious_fault is just BUG()?
It's probably only important if you care about the stack trace for the
BUG() case. But BP is clobbered anyway so I guess it doesn't matter.
> There is no macro currently to support CONFIG_DEBUG_BUGVERBOSE in
> assembly code, but it's also fine if you just change the call to ud2.
That would be one way to make objtool happy.
--
Josh
next prev parent reply other threads:[~2019-07-15 12:37 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 0:36 [PATCH 00/22] x86, objtool: several fixes/improvements Josh Poimboeuf
2019-07-15 0:36 ` [PATCH 01/22] x86/paravirt: Fix callee-saved function ELF sizes Josh Poimboeuf
2019-07-15 4:58 ` Juergen Gross
2019-07-15 12:43 ` Josh Poimboeuf
2019-07-15 0:36 ` [PATCH 02/22] x86/kvm: Fix fastop function ELF metadata Josh Poimboeuf
2019-07-15 9:05 ` Paolo Bonzini
2019-07-15 0:36 ` [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx_vmenter() Josh Poimboeuf
2019-07-15 9:04 ` Paolo Bonzini
2019-07-15 12:37 ` Josh Poimboeuf [this message]
2019-07-15 13:03 ` Paolo Bonzini
2019-07-15 13:35 ` Josh Poimboeuf
2019-07-15 18:17 ` Paolo Bonzini
2019-07-15 0:36 ` [PATCH 04/22] x86/kvm: Don't call kvm_spurious_fault() from .fixup Josh Poimboeuf
2019-07-15 9:07 ` Paolo Bonzini
2019-07-15 12:40 ` Josh Poimboeuf
2019-07-15 13:05 ` Paolo Bonzini
2019-07-15 13:25 ` Josh Poimboeuf
2019-07-15 18:16 ` Paolo Bonzini
2019-07-15 0:37 ` [PATCH 05/22] x86/entry: Fix thunk function ELF sizes Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 06/22] x86/head/64: Annotate start_cpu0() as non-callable Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 07/22] x86/uaccess: Remove ELF function annotation from copy_user_handle_tail() Josh Poimboeuf
2019-07-16 18:16 ` Nick Desaulniers
2019-07-16 18:51 ` Peter Zijlstra
2019-07-15 0:37 ` [PATCH 08/22] x86/uaccess: Don't leak AC flag into fentry from mcsafe_handle_tail() Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 09/22] x86/uaccess: Remove redundant CLACs in getuser/putuser error paths Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 10/22] bpf: Disable GCC -fgcse optimization for ___bpf_prog_run() Josh Poimboeuf
2019-07-16 18:15 ` Nick Desaulniers
2019-07-16 23:02 ` Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 11/22] objtool: Add mcsafe_handle_tail() to the uaccess safe list Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 12/22] objtool: Track original function across branches Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 13/22] objtool: Refactor function alias logic Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 14/22] objtool: Warn on zero-length functions Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 15/22] objtool: Change dead_end_function() to return boolean Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 16/22] objtool: Do frame pointer check before dead end check Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 17/22] objtool: Refactor sibling call detection logic Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 18/22] objtool: Refactor jump table code Josh Poimboeuf
2019-07-15 9:38 ` Peter Zijlstra
2019-07-15 0:37 ` [PATCH 19/22] objtool: Support repeated uses of the same C jump table Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 20/22] objtool: Fix seg fault on bad switch table entry Josh Poimboeuf
2019-07-15 17:24 ` Nick Desaulniers
2019-07-15 17:29 ` Josh Poimboeuf
2019-07-18 23:02 ` Nick Desaulniers
2019-07-15 0:37 ` [PATCH 21/22] objtool: convert insn type to enum Josh Poimboeuf
2019-07-15 0:37 ` [PATCH 22/22] objtool: Support conditional retpolines Josh Poimboeuf
2019-07-15 9:52 ` [PATCH 00/22] x86, objtool: several fixes/improvements Peter Zijlstra
2019-07-15 19:38 ` Josh Poimboeuf
2019-07-15 21:45 ` Nick Desaulniers
2019-07-16 23:17 ` Josh Poimboeuf
2019-07-18 22:26 ` Nick Desaulniers
2019-09-27 20:24 ` Nick Desaulniers
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