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Bug 1727930

Summary: [RPMDiff] Lost -fPIC in the static library
Product: Red Hat Enterprise Linux 8 Reporter: Honza Horak <hhorak>
Component: gccAssignee: Marek Polacek <mpolacek>
gcc sub component: system-version QA Contact: qe-baseos-tools-bugs
Status: CLOSED NOTABUG Docs Contact:
Severity: unspecified    
Priority: unspecified CC: ahajkova, databases-maint, esandeen, fweimer, jakub, law, mmuzila, ohudlick, pkubat, vdanek
Version: 8.1   
Target Milestone: rc   
Target Release: 8.1   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-07-16 15:17:27 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: 1606978, 1714923    

Comment 4 Florian Weimer 2019-07-10 09:45:09 UTC 
The rpmdiff check is not very good.  It really should look at the actual relocations and check if the link editor can resolve them to position-independent code.

The more recent build has optimized out all stack protector usage.  Before:

Relocation section [ 6] '.rela.text' for section [ 5] '.text' at offset 0xc98 contains 17 entries:
  Offset              Type            Value               Addend Name
  0x0000000000000080  AARCH64_CALL26  000000000000000000      +0 __os_urealloc
  0x000000000000014c  AARCH64_CALL26  000000000000000000      +0 __os_umalloc
  0x0000000000000174  AARCH64_CALL26  000000000000000000      +0 memcpy
  0x00000000000001b4  AARCH64_CALL26  000000000000000000      +0 __os_realloc
  0x0000000000000204  AARCH64_ADR_GOT_PAGE 000000000000000000      +0 __stack_chk_guard
  0x0000000000000210  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x0000000000000290  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x00000000000002b0  AARCH64_JUMP26  000000000000000000      +0 __db_pgfmt
  0x0000000000000314  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x0000000000000334  AARCH64_JUMP26  000000000000000000      +0 __db_retcopy
  0x00000000000003a8  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x00000000000003cc  AARCH64_JUMP26  000000000000000000      +0 __heapc_gsplit
  0x00000000000003d4  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x0000000000000400  AARCH64_JUMP26  000000000000000000      +0 __db_goff
  0x0000000000000404  AARCH64_LD64_GOT_LO12_NC 000000000000000000      +0 __stack_chk_guard
  0x0000000000000424  AARCH64_JUMP26  000000000000000000      +0 __db_goff
  0x0000000000000428  AARCH64_CALL26  000000000000000000      +0 __stack_chk_fail

After:

Relocation section [ 6] '.rela.text' for section [ 5] '.text' at offset 0x14f0 contains 11 entries:
  Offset              Type            Value               Addend Name
  0x0000000000000080  AARCH64_CALL26  000000000000000000      +0 __os_urealloc
  0x000000000000014c  AARCH64_CALL26  000000000000000000      +0 __os_umalloc
  0x0000000000000174  AARCH64_CALL26  000000000000000000      +0 memcpy
  0x00000000000001b4  AARCH64_CALL26  000000000000000000      +0 __os_realloc
  0x0000000000000270  AARCH64_JUMP26  000000000000000000      +0 __db_retcopy
  0x0000000000000284  AARCH64_JUMP26  000000000000000000      +0 __db_pgfmt
  0x00000000000002f0  AARCH64_JUMP26  000000000000000000      +0 __db_retcopy
  0x0000000000000344  AARCH64_JUMP26  000000000000000000      +0 __db_retcopy
  0x0000000000000364  AARCH64_JUMP26  000000000000000000      +0 __heapc_gsplit
  0x0000000000000370  AARCH64_JUMP26  000000000000000000      +0 __db_goff
  0x000000000000037c  AARCH64_JUMP26  000000000000000000      +0 __db_goff

The optimization looks correct because the functions do not contain any addressable local variables.

I do not know why it wasn't applied by GCC before.
Comment 5 Marek Polacek 2019-07-10 12:49:44 UTC 
As I recently found out:

  Debugging an aarch64 problem re -fPIC:
  https://rpmdiff.engineering.redhat.com/run/408856/7/
  Bisected it to r270414 on gcc-8-branch.  After the revision, a call to
  __stack_chk_guard is gone, and so is R_AARCH64_LD64_GOT_LO12_NC.  And
  the RPMDiff check uses eu-readelf --reloc | grep GOT to check for -fPIC.
Comment 6 Eric Sandeen 2019-07-10 14:35:54 UTC 
An e2fsprogs errata is also blocked by this.
Comment 7 Eric Sandeen 2019-07-10 14:36:30 UTC 
https://rpmdiff.engineering.redhat.com/run/411165/
Comment 8 Marek Polacek 2019-07-16 12:43:18 UTC 
This is not a GCC bug AFAICS so I'll close it out.
Comment 9 Jeff Law 2019-07-16 15:17:27 UTC 
Not a GCC bug.  It would best be described as a false positive from rpmdiff due to its lame approach to detecting PIC.