Bug 1529979

Summary: gcc: incorrect CFI information on i386 with -fstack-clash-protection.
Product: [Fedora] Fedora Reporter: Florian Weimer <fweimer>
Component: gccAssignee: Jeff Law <law>
Status: CLOSED EOL QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 28CC: aoliva, davejohansen, fweimer, jakub, jwakely, law, mpolacek
Target Milestone: ---   
Target Release: ---   
Hardware: i386   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1529981 (view as bug list) Environment:
Last Closed: 2019-05-28 19:42:35 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1529549, 1529981    
Attachments:
Description Flags
unwind.i none

Description Florian Weimer 2017-12-31 16:08:23 UTC 
Created attachment 1374983 [details]
unwind.i

Description of problem:

The attached program, when compiled using

gcc -fPIC -O2 -fgnu89-inline-fstack-clash-protection -c unwind.i

produces invalid CFI instructions for __GI___pthread_unwind:

__GI___pthread_unwind:
.LFB55:
        .cfi_startproc
        pushl   %esi
        .cfi_def_cfa_offset 8
        .cfi_offset 6, -8
        pushl   %ebx
        .cfi_def_cfa_offset 12
        .cfi_offset 3, -12
        pushl   %esi
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        popl    %esi
        .cfi_restore 6
        .cfi_def_cfa_offset 12
        call    __x86.get_pc_thunk.bx
        addl    $_GLOBAL_OFFSET_TABLE_, %ebx
        subl    $8, %esp
        .cfi_def_cfa_offset 20
        movl    %eax, %esi

The problem is that the .cfi_restore for %esi does not restore the original location at offset 8, but essentially declares that the register will not be clobbered further below, while in fact it is used to store the function argument (__pthread_unwind is compiled with __attribute__ ((regparm (1)))).

As a result, the libgcc unwinder restores the wrong value for %esi, leading to bug 1529549.

Version-Release number of selected component (if applicable):

gcc-7.2.1-4.fc28.i686
Comment 1 Jeff Law 2018-01-01 20:39:46 UTC 
Mine, obviously.  I'll be on it first thing tomorrow.
Comment 2 Fedora End Of Life 2018-02-20 15:38:37 UTC 
This bug appears to have been reported against 'rawhide' during the Fedora 28 development cycle.
Changing version to '28'.
Comment 3 Ben Cotton 2019-05-02 22:01:20 UTC 
This message is a reminder that Fedora 28 is nearing its end of life.
On 2019-May-28 Fedora will stop maintaining and issuing updates for
Fedora 28. It is Fedora's policy to close all bug reports from releases
that are no longer maintained. At that time this bug will be closed as
EOL if it remains open with a Fedora 'version' of '28'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not 
able to fix it before Fedora 28 is end of life. If you would still like 
to see this bug fixed and are able to reproduce it against a later version 
of Fedora, you are encouraged  change the 'version' to a later Fedora 
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events. Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.
Comment 4 Ben Cotton 2019-05-28 19:42:35 UTC 
Fedora 28 changed to end-of-life (EOL) status on 2019-05-28. Fedora 28 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.