[Bug 1830796] Re: [Bionic][ARM64]Failure debugging linux kernel

[Manoj Iyer]

** Description changed:

  [Impact]
  GDB fails to debug ARM64 vmlinux debug image with proc/kcore information. For example it is unable to print values of variables like 'jiffies_64'.
  
  [Test]
  # gdb /usr/lib/debug/boot/vmlinux-4.18.0-20-generic  /proc/kcore
  [New process 1]
  Core was generated by `BOOT_IMAGE=/boot/vmlinuz-4.18.0-20-generic root=UUID=edb5e5a7-8272-4e13-aa25-37'.
  #0  0x0000000000000000 in ?? ()
  (gdb) p jiffies_64
  Cannot access memory at address 0xffff000009616980
  (gdb)
  
  [Fix]
  This issue was fixed upstream (git://sourceware.org/git/binutils-gdb.git) by the following patch:
  8727de56b0  Fix tagged pointer support
  
  [Regression Potential]
- The risk of regression after applying this patch is low.
+ The risk of regression after applying this patch could be to architectures other than ARM64 due to changes to gdb/util.c. Please see comment #2 where I have tested the PPA package on a ppc64el system and found it does not introduce any regressions.

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https://bugs.launchpad.net/bugs/1830796

Title:
  [Bionic][ARM64]Failure debugging linux kernel

Status in gdb package in Ubuntu:
  In Progress

Bug description:
  [Impact]
  GDB fails to debug ARM64 vmlinux debug image with proc/kcore information. For example it is unable to print values of variables like 'jiffies_64'.

  [Test]
  # gdb /usr/lib/debug/boot/vmlinux-4.18.0-20-generic  /proc/kcore
  [New process 1]
  Core was generated by `BOOT_IMAGE=/boot/vmlinuz-4.18.0-20-generic root=UUID=edb5e5a7-8272-4e13-aa25-37'.
  #0  0x0000000000000000 in ?? ()
  (gdb) p jiffies_64
  Cannot access memory at address 0xffff000009616980
  (gdb)

  [Fix]
  This issue was fixed upstream (git://sourceware.org/git/binutils-gdb.git) by the following patch:
  8727de56b0  Fix tagged pointer support

  [Regression Potential]
  The risk of regression after applying this patch could be to architectures other than ARM64 due to changes to gdb/util.c. Please see comment #2 where I have tested the PPA package on a ppc64el system and found it does not introduce any regressions.

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