Thanks Bhupesh -- the fix is queued for crash-7.2.2: https://github.com/crash-utility/crash/commit/a002f07040972a3d4b0743811e643bfba7b8cc99 Dave ----- Original Message ----- > Hi Dave, > > On Wed, Feb 28, 2018 at 9:09 PM, Dave Anderson <anderson@xxxxxxxxxx> wrote: > > > > Hi Bhupesh, > > > > Try this patch: > > > > $ diff --git a/filesys.c b/filesys.c > > index 1b44ad5..74728f1 > > --- a/filesys.c > > +++ b/filesys.c > > @@ -625,7 +625,7 @@ find_booted_kernel(void) > > > > if (mount_point(kernel) || > > !file_readable(kernel) || > > - !is_elf_file(kernel)) > > + !is_kernel(kernel)) > > continue; > > > > if (CRASHDEBUG(1)) > > diff --git a/symbols.c b/symbols.c > > index 4db9af7..7910f53 > > --- a/symbols.c > > +++ b/symbols.c > > @@ -3488,7 +3488,8 @@ is_kernel(char *file) > > > > if (endian_mismatch(file, elf64->e_ident[EI_DATA], 0)) > > goto bailout; > > - } > > + } else > > + return FALSE; > > > > bailout: > > return(is_bfd_format(file)); > > > > Thanks, > > Dave > > I tried this patch and it seems to work fine on my arm64 system. > Please feel free to add my Tested-by for the patch. > > Thanks. > > > > ----- Original Message ----- > >> Hi Bhupesh, > >> > >> Thanks -- mystery solved! > >> > >> I kind of hate to simply use the file name string as the qualifier, > >> though. > >> Looking at the ELF headers of the vmlinux.o and vmlinux file, there are > >> several notable differences: > >> > >> $ readelf -a vmlinux > >> ELF Header: > >> Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 > >> Class: ELF64 > >> Data: 2's complement, little endian > >> Version: 1 (current) > >> OS/ABI: UNIX - System V > >> ABI Version: 0 > >> Type: EXEC (Executable file) > >> Machine: AArch64 > >> Version: 0x1 > >> Entry point address: 0xffff000008080000 > >> Start of program headers: 64 (bytes into file) > >> Start of section headers: 186677936 (bytes into file) > >> Flags: 0x0 > >> Size of this header: 64 (bytes) > >> Size of program headers: 56 (bytes) > >> Number of program headers: 4 > >> Size of section headers: 64 (bytes) > >> Number of section headers: 42 > >> Section header string table index: 41 > >> ... > >> > >> > >> $ readelf -a vmlinux.o > >> ELF Header: > >> Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 > >> Class: ELF64 > >> Data: 2's complement, little endian > >> Version: 1 (current) > >> OS/ABI: UNIX - System V > >> ABI Version: 0 > >> Type: REL (Relocatable file) > >> Machine: AArch64 > >> Version: 0x1 > >> Entry point address: 0x0 > >> Start of program headers: 0 (bytes into file) > >> Start of section headers: 478638376 (bytes into file) > >> Flags: 0x0 > >> Size of this header: 64 (bytes) > >> Size of program headers: 0 (bytes) > >> Number of program headers: 0 > >> Size of section headers: 64 (bytes) > >> Number of section headers: 34816 > >> Section header string table index: 34815 > >> ... > >> > >> There is the "Type", the "Entry point address", and perhaps most notably, > >> the vmlinux.o's "Number of program headers:" count of 0, which obviously > >> would preclude the file from being usable. > >> > >> I would prefer to beef up the currently-existing is_kernel() function, > >> and use it instead of is_elf_file(). Let me take a look at what works. > >> > >> Thanks, > >> Dave > >> > >> > >> > >> ----- Original Message ----- > >> > I found this particular issue while compiling and installing > >> > a kernel from source on a RHEL arm64 machine. I used the following > >> > commands to build and install the kernel from source: > >> > > >> > # make olddefconfig > >> > # make > >> > # make modules_install INSTALL_MOD_STRIP=1 && make install > >> > > >> > This compiles and installs both 'vmlinux' and 'vmlinux.o' at > >> > the following standard location - '/lib/modules/<kernel>/build/ > >> > > >> > Now the problem can be reproduced using the following steps: > >> > 1. Update grub to boot the freshly compiled kernel. > >> > 2. Reboot machine. > >> > 3. Now, run crash on live system, it errors out with the following > >> > messages: > >> > > >> > crash: invalid kernel virtual address: 8470 type: "possible" > >> > WARNING: cannot read cpu_possible_map > >> > crash: invalid kernel virtual address: 8270 type: "present" > >> > WARNING: cannot read cpu_present_map > >> > crash: invalid kernel virtual address: 8070 type: "online" > >> > WARNING: cannot read cpu_online_map > >> > crash: invalid kernel virtual address: 8670 type: "active" > >> > WARNING: cannot read cpu_active_map > >> > > >> > crash: cannot resolve "_stext" > >> > > >> > 4. Enabling some debug messages in 'find_booted_kernel()' function > >> > tells us that it finds 'vmlinux.o' earlier than 'vmlinux' and accepts > >> > that as the kernel being boot'ed: > >> > > >> > find_booted_kernel: check: /lib/modules/4.14.0/build/vmlinux.o > >> > find_booted_kernel: found: /lib/modules/4.14.0/build/vmlinux.o > >> > > >> > 5. Now the problem happens due to following check inside > >> > 'find_booted_kernel()' function: > >> > > >> > if (mount_point(kernel) || > >> > !file_readable(kernel) || > >> > !is_elf_file(kernel)) > >> > continue; > >> > > >> > 6. Since 'vmlinux.o' is a elf file, is readable and is not > >> > mount'able, so the check in point 5 fails and we incorrectly > >> > accept this as the kernel being boot'ed, even though > >> > there was a 'vmlinux' present inside > >> > '/lib/modules/<kernel>/build'. > >> > > >> > 7. Now, later when crash tries to access symbols (like _stext) > >> > using this kernel symbol file, we see errors. > >> > > >> > Fix this by skipping 'vmlinux.o' from the check in point 5, > >> > so that we can select 'vmlinux' correctly as the kernel file. > >> > > >> > After this fix, crash no longer errors out and we can use > >> > full functionality on the crash prompt. > >> > > >> > Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx> > >> > --- > >> > filesys.c | 14 +++++++++++++- > >> > 1 file changed, 13 insertions(+), 1 deletion(-) > >> > > >> > diff --git a/filesys.c b/filesys.c > >> > index 1b44ad5cefa8..9f240d6115a1 100644 > >> > --- a/filesys.c > >> > +++ b/filesys.c > >> > @@ -623,9 +623,21 @@ find_booted_kernel(void) > >> > > >> > sprintf(kernel, "%s%s", searchdirs[i], dp->d_name); > >> > > >> > + /* We may run into a special case with > >> > + * 'vmlinux.o' been present inside > >> > + * '/lib/modules/<kernel>/build/', > >> > + * which has some special characteristics - > >> > + * this is a elf file, is readable and is not > >> > + * mount'able. > >> > + * > >> > + * So we need to handle this properly here to > >> > + * make sure that we get to the real 'vmlinux' > >> > + * rather than the 'vmlinux.o' > >> > + */ > >> > if (mount_point(kernel) || > >> > !file_readable(kernel) || > >> > - !is_elf_file(kernel)) > >> > + !is_elf_file(kernel) || > >> > + !(strcmp(dp->d_name, "vmlinux.o"))) > >> > continue; > >> > > >> > if (CRASHDEBUG(1)) > >> > -- > >> > 2.7.4 > >> > > >> > > >> > >> -- > >> Crash-utility mailing list > >> Crash-utility@xxxxxxxxxx > >> https://www.redhat.com/mailman/listinfo/crash-utility > >> > -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
