From: ASOU Masato <takeasou.masato@gmail.com>
Subject: Re: lldb: fails to read a process core file (regression)
To: YASUOKA Masahiko <yasuoka@openbsd.org>, Yuichiro NAITO <naito.yuichiro@gmail.com>
Cc: asou@openbsd.org, tech@openbsd.org
Date: Thu, 1 Aug 2024 10:47:24 +0900

Thank Yuichiro.

I was tested this patch on my AMD box to investigate kernel core and process
core. And it's work fine for me.

Committed OpenBSD CVS.
--
ASOU Masato

2024年7月31日(水) 17:31 YASUOKA Masahiko <yasuoka@openbsd.org>:
>
> Asou-san,
>
> Can you handle this?
>
> ok yasuoka
>
> On Wed, 31 Jul 2024 16:38:25 +0900 (JST)
> Yuichiro NAITO <naito.yuichiro@gmail.com> wrote:
> > I received a mail personally that reports lldb fails to read a process core
> > file. It's a regression of my kernel core file support patch. My apologies.
> >
> > The ProcessOpenBSDKernel class opens a core file via kvm_open(3).
> > The kvm_open(3) succeeds in opening a core file even if it is a process core.
> > So the OpenBSDKernel plugin is used for a process core file but can't analyze
> > it.
> >
> > If a process core file is passed to the ProcessOpenBSDKernel class, its
> > instantiation should fail. A process core file is an ELF binary. I add
> > the check logic to see whether an ELF binary or not and make it fail
> > instantiation in case of an ELF binary.
> >
> > OK?
> >
> > diff --git a/gnu/llvm/lldb/source/Plugins/Process/OpenBSDKernel/ProcessOpenBSDKernel.cpp b/gnu/llvm/lldb/source/Plugins/Process/OpenBSDKernel/ProcessOpenBSDKernel.cpp
> > index 300a35d4051..8016399586f 100644
> > --- a/gnu/llvm/lldb/source/Plugins/Process/OpenBSDKernel/ProcessOpenBSDKernel.cpp
> > +++ b/gnu/llvm/lldb/source/Plugins/Process/OpenBSDKernel/ProcessOpenBSDKernel.cpp
> > @@ -19,6 +19,7 @@
> >  #define _KERNEL
> >  #include <machine/cpu.h>
> >  #include <sys/proc.h>
> > +#include <sys/exec_elf.h>
> >  #undef _KERNEL
> >  #endif
> >
> > @@ -60,6 +61,14 @@ lldb::ProcessSP ProcessOpenBSDKernel::CreateInstance(lldb::TargetSP target_sp,
> >    ModuleSP executable = target_sp->GetExecutableModule();
> >    if (crash_file && !can_connect && executable) {
> >  #if defined(__OpenBSD__)
> > +    char buf[4];
> > +    FILE *fp = fopen(crash_file->GetPath().c_str(), "r");
> > +    if (fp == NULL)
> > +      return nullptr;
> > +    size_t r = fread(buf, 1, sizeof(buf), fp);
> > +    fclose(fp);
> > +    if (r != sizeof(buf) || memcmp(buf, ELFMAG, sizeof(buf)) == 0)
> > +      return nullptr;
> >      kvm_t *kvm =
> >          kvm_open(executable->GetFileSpec().GetPath().c_str(),
> >                crash_file->GetPath().c_str(), nullptr, O_RDONLY, nullptr);
> >
> > --
> > Yuichiro NAITO (naito.yuichiro@gmail.com)
> >
> >
>