linux-sgx.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sean Christopherson <sean.j.christopherson@intel.com>
To: "Xing, Cedric" <cedric.xing@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	linux-sgx@vger.kernel.org
Subject: Re: [PATCH for_v23 16/16] x86/vdso: sgx: Rework __vdso_sgx_enter_enclave() to prefer "no callback"
Date: Wed, 16 Oct 2019 15:53:57 -0700	[thread overview]
Message-ID: <20191016225357.GB8711@linux.intel.com> (raw)
In-Reply-To: <96a8533b-cbcb-1701-393a-a94552ff717f@intel.com>

On Wed, Oct 16, 2019 at 03:18:05PM -0700, Xing, Cedric wrote:
> On 10/10/2019 4:59 PM, Sean Christopherson wrote:
> >On Thu, Oct 10, 2019 at 10:49:59AM -0700, Xing, Cedric wrote:
> >>On 10/9/2019 12:10 PM, Sean Christopherson wrote:
> >>>On Wed, Oct 09, 2019 at 11:00:55AM -0700, Xing, Cedric wrote:
> >>>>On 10/7/2019 9:46 PM, Sean Christopherson wrote:
> >>>>>-	/* Align stack per x86_64 ABI. The original %rsp is saved in %rbx to be
> >>>>>-	 * restored after the exit handler returns. */
> >>>>>+
> >>>>>+	/* Invoke userspace's exit handler if one was provided. */
> >>>>>+.Lhandle_exit:
> >>>>>+	cmp	$0, 0x20(%rbp)
> >>>>>+	jne	.Linvoke_userspace_handler
> >>>>>+
> >>>>>+.Lout:
> >>>>>+	leave
> >>>>>+	.cfi_def_cfa		%rsp, 8
> >>>>>+	ret
> >>>>>+
> >>>>>+.Linvalid_leaf:
> >>>>
> >>>>Please set frame pointer back to %rbp here, or stack unwinding will fail.
> >>>
> >>>Sorry, coffee isn't doing it's job, what's getting crushed, and where?
> >>
> >>The frame pointer was %rbp but you changed it to %rsp 3 lines ago. That's
> >>correct after "leave" and execution won't pass "ret". But the unwinder
> >>doesn't know. So you have to restore frame pointer after "ret", by
> >>	.cfi_def_cfa		%rbp, 16
> >
> >Isn't the proper fix to move ".cfi_endproc" here?  Which I incorrectly
> >left after the RET for the retpoline.
> 
> No. .cfi_endproc is used by the unwinder to determine if an address falls
> within a function. Its location has nothing to do with where RET is but
> shall always be at the end of the whole function.
> 
> .cfi_def_cfa tells the unwinder where the call frame starts. At here, the
> call frame starts at %rbp+16 but not %rsp+8, so ".cfi_def_cfa %rbp, 16" is a
> must.

Ahh, I understand now, hopefully.  I was thinking the .cfi directives
would magically understand the control flow.  Thanks!

> >>>>>+.Lhandle_exception:
> >>>>>+	mov	0x18(%rbp), %rcx
> >>>>>+	test    %rcx, %rcx
> >>>>>+	je	.Lskip_exception_info
> >>>>

  reply	other threads:[~2019-10-16 22:53 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-08  4:45 [PATCH for_v23 00/16] x86/vdso: sgx: Major vDSO cleanup Sean Christopherson
2019-10-08  4:45 ` [PATCH for_v23 01/16] x86/vdso: sgx: Drop the pseudocode "documentation" Sean Christopherson
2019-10-08  4:45 ` [PATCH for_v23 02/16] x86/vdso: sgx: Do not use exception info to pass success/failure Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 03/16] x86/vdso: sgx: Rename the enclave exit handler typedef Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 04/16] x86/vdso: sgx: Move enclave exit handler declaration to UAPI header Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 05/16] x86/vdso: sgx: Add comment regarding kernel-doc shenanigans Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 06/16] x86/vdso: sgx: Rewrite __vdso_sgx_enter_enclave() function comment Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 07/16] selftests/x86: Fix linker warning in SGX selftest Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 08/16] selftests/x86/sgx: Use getauxval() to retrieve the vDSO base address Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 09/16] selftests/x86/sgx: Add helper function and macros to assert results Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 10/16] selftests/x86/sgx: Handle setup failures via test assertions Sean Christopherson
2019-10-15 10:16   ` Jarkko Sakkinen
2019-10-15 10:24     ` Jarkko Sakkinen
2019-10-15 10:25       ` Jarkko Sakkinen
2019-10-15 11:03         ` Jarkko Sakkinen
2019-10-15 16:27           ` Sean Christopherson
2019-10-16 10:20             ` Jarkko Sakkinen
2019-10-16 20:21         ` Sean Christopherson
2019-10-15 16:18     ` Sean Christopherson
2019-10-16 10:19       ` Jarkko Sakkinen
2019-10-08  4:46 ` [PATCH for_v23 11/16] selftests/x86/sgx: Sanitize the types for sgx_call()'s input params Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 12/16] selftests/x86/sgx: Move existing sub-test to a separate helper Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 13/16] selftests/x86/sgx: Add a test of the vDSO exception reporting mechanism Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 14/16] selftests/x86/sgx: Add test of vDSO with basic exit handler Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 15/16] selftests/x86/sgx: Add sub-test for exception behavior with " Sean Christopherson
2019-10-08  4:46 ` [PATCH for_v23 16/16] x86/vdso: sgx: Rework __vdso_sgx_enter_enclave() to prefer "no callback" Sean Christopherson
2019-10-09 18:00   ` Xing, Cedric
2019-10-09 19:10     ` Sean Christopherson
2019-10-10  0:21       ` Sean Christopherson
2019-10-10 17:49       ` Xing, Cedric
2019-10-10 23:59         ` Sean Christopherson
2019-10-16 22:18           ` Xing, Cedric
2019-10-16 22:53             ` Sean Christopherson [this message]
2019-10-10  8:10 ` [PATCH for_v23 00/16] x86/vdso: sgx: Major vDSO cleanup Jarkko Sakkinen
2019-10-10 16:08   ` Sean Christopherson
2019-10-14 21:04     ` Jarkko Sakkinen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191016225357.GB8711@linux.intel.com \
    --to=sean.j.christopherson@intel.com \
    --cc=cedric.xing@intel.com \
    --cc=jarkko.sakkinen@linux.intel.com \
    --cc=linux-sgx@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).