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[34.79.100.158]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-395c8881187sm14080655f8f.41.2025.03.17.01.47.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Mar 2025 01:47:24 -0700 (PDT) Date: Mon, 17 Mar 2025 08:47:20 +0000 From: Brendan Jackman To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Nathan Chancellor Subject: Re: [PATCH 04/13] objtool: Update documentation Message-ID: References: <2552ee8b48631127bf269359647a7389edf5f002.1741975349.git.jpoimboe@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2552ee8b48631127bf269359647a7389edf5f002.1741975349.git.jpoimboe@kernel.org> On Fri, Mar 14, 2025 at 12:29:02PM -0700, Josh Poimboeuf wrote: > Fix some outdated information in the objtool doc. Regarding the switch from ENTRY/ENDPROC to SYM_FUNC_{START,END}, would you mind adding a bit more context to the commit message for the benefit of ignorami like me? BTW in tip/objtool/core include/linux/objtool.h still says: > Such normal callable functions > are annotated with the ENTRY/ENDPROC macros. And o we also wanna update include/linux/linkage.h to mention that these macros are deprecated? > Signed-off-by: Josh Poimboeuf > --- > tools/objtool/Documentation/objtool.txt | 95 ++++++++++++++----------- > 1 file changed, 53 insertions(+), 42 deletions(-) > > diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt > index 87950a7aaa17..28ac57b9e102 100644 > --- a/tools/objtool/Documentation/objtool.txt > +++ b/tools/objtool/Documentation/objtool.txt > @@ -28,6 +28,15 @@ Objtool has the following features: > sites, enabling the kernel to patch them inline, to prevent "thunk > funneling" for both security and performance reasons > > +- Return thunk validation -- validates return thunks are used for > + certain CPU mitigations including Retbleed and SRSO > + > +- Return thunk annotation -- annotates all return thunk sites so kernel > + can patch them inline, depending on enabled mitigations > + > +- Return thunk training valiation -- validate that all entry paths s/valiation/validation Also did you mean "untraining"? > + untrain a "safe return" before the first return (or call) Nit - assuming this is about the SRSO mitigation I think it's better to just refer concretely to "Safe RET" here (with the capitalisation).