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powerpc: Enable execve syscall exit tracepoint

Steve Best requested to merge sfbest/centos-stream-9:2095526 into main

Bugzilla: http://bugzilla.redhat.com/2095526

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=46210611

Tested: Did sanity boot testing on power 9 (ibm-p9z-06-lp1) system.

commit ec6d0dde71d760aa60316f8d1c9a1b0d99213529 Author: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Date: Thu Jun 9 16:03:28 2022 +0530

powerpc: Enable execve syscall exit tracepoint

On execve[at], we are zero'ing out most of the thread register state
including gpr[0], which contains the syscall number. Due to this, we
fail to trigger the syscall exit tracepoint properly. Fix this by
retaining gpr[0] in the thread register state.

Before this patch:
               cat-123     [000] .....    61.449351: sys_execve(filename:
  7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8)
               cat-124     [000] .....    62.428481: sys_execve(filename:
  7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8)
              echo-125     [000] .....    65.813702: sys_execve(filename:
  7fffa6b23378, argv: 7fffa6b233a0, envp: 7fffa6b233b0)
              echo-125     [000] .....    65.822214: sys_execveat(fd: 0,
  filename: 1009ac48, argv: 7ffff65d0c98, envp: 7ffff65d0ca8, flags: 0)

After this patch:
               cat-127     [000] .....   100.416262: sys_execve(filename:
  7fffa41b3448, argv: 7fffa41b33e0, envp: 7fffa41b33f8)
               cat-127     [000] .....   100.418203: sys_execve -> 0x0
              echo-128     [000] .....   103.873968: sys_execve(filename:
  7fffa41b3378, argv: 7fffa41b33a0, envp: 7fffa41b33b0)
              echo-128     [000] .....   103.875102: sys_execve -> 0x0
              echo-128     [000] .....   103.882097: sys_execveat(fd: 0,
  filename: 1009ac48, argv: 7fffd10d2148, envp: 7fffd10d2158, flags: 0)
              echo-128     [000] .....   103.883225: sys_execveat -> 0x0

Cc: stable@vger.kernel.org
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Sumit Dubey2 <Sumit.Dubey2@ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220609103328.41306-1-naveen.n.rao@linux.vnet.ibm.com

Signed-off-by: Steve Best sbest@redhat.com

Edited by Steve Best

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