Re: [PATCH] kprobes: Enable tracing for mololithic kernel images
From: Christoph Hellwig <hch@lst.de>
Date: 2022-06-09 03:49:10
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linux-mips, linux-modules, linux-riscv, linux-s390, lkml, sparclinux
st@kernel.org>, Will Deacon [off-list ref], Masahiro Yamada [off-list ref], Jarkko Sakkinen [off-list ref], Sami Tolvanen [off-list ref], "Naveen N. Rao" [off-list ref], Marco Elver [off-list ref], Kees Cook [off-list ref], Steven Rostedt [off-list ref], Nathan Chancellor [off-list ref], "Russell King \(Oracle\)" [off-list ref], Mark Brown [off-list ref], Borislav Petkov [off-list ref], Alexander Egorenkov [off-list ref], Thomas Bogendoerfer [off-list ref], Parisc List [off-list ref], Nathaniel McCallum [off-list ref], Dmitry Torokhov [off-list ref], "David S. Miller" [off-list ref], "Kirill A. Shutemov" [off-list ref], Tobias Huschle [off-list ref], "Peter Zijlstra \(Intel\)" [off-list ref], "H. Peter Anvin" [off-list ref], sparclinux [off-list ref], Tiezhu Yang <yangtiezhu@loongs on.cn>, Miroslav Benes [off-list ref], Chen Zhongjin [off-list ref], Ard Biesheuvel [off-list ref], the arch/x86 maintainers [off-list ref], Russell King [off-list ref], linux-riscv [off-list ref], Ingo Molnar [off-list ref], Aaron Tomlin [off-list ref], Albert Ou [off-list ref], Heiko Carstens [off-list ref], Liao Chang [off-list ref], Paul Walmsley [off-list ref], Josh Poimboeuf [off-list ref], Thomas Richter [off-list ref], "open list:BROADCOM NVRAM DRIVER" [off-list ref], Changbin Du [off-list ref], Palmer Dabbelt [off-list ref], linuxppc-dev [off-list ref], linux-modules@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" [off-list ref] On Wed, Jun 08, 2022 at 01:26:19PM -0700, Luis Chamberlain wrote:
No, that was removed because it has only one user.
That is only part of the story. The other part is that the overall kernel simply does not have any business allocating exutable memory. Executable memory is a very special concept for modules or module-like code like kprobes, and should not be exposed as a general concept. Especially as executable memory really should not also be writable for security reasons. In other words, we should actually never allocate executable memory, every. We might seal memory and then mark it executable after having written to it, which is how modules and kprobes are implemented on all modern Linux ports anyway.