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5befc25f5c
commit ac5ceccce5 upstream.
When the ORC unwinder is invoked for an oops caused by IP==0,
it currently has no idea what to do because there is no debug information
for the stack frame of NULL.
But if RIP is NULL, it is very likely that the last successfully executed
instruction was an indirect CALL/JMP, and it is possible to unwind out in
the same way as for the first instruction of a normal function. Hardcode
a corresponding ORC entry.
With an artificially-added NULL call in prctl_set_seccomp(), before this
patch, the trace is:
Call Trace:
? __x64_sys_prctl+0x402/0x680
? __ia32_sys_prctl+0x6e0/0x6e0
? __do_page_fault+0x457/0x620
? do_syscall_64+0x6d/0x160
? entry_SYSCALL_64_after_hwframe+0x44/0xa9
After this patch, the trace looks like this:
Call Trace:
__x64_sys_prctl+0x402/0x680
? __ia32_sys_prctl+0x6e0/0x6e0
? __do_page_fault+0x457/0x620
do_syscall_64+0x6d/0x160
entry_SYSCALL_64_after_hwframe+0x44/0xa9
prctl_set_seccomp() still doesn't show up in the trace because for some
reason, tail call optimization is only disabled in builds that use the
frame pointer unwinder.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-kbuild@vger.kernel.org
Link: https://lkml.kernel.org/r/20190301031201.7416-2-jannh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.