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[34.90.50.93]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6584b92b66dsm5234876a12.20.2026.01.26.03.21.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jan 2026 03:21:07 -0800 (PST) Date: Mon, 26 Jan 2026 11:21:04 +0000 From: Matt Bobrowski To: Alan Maguire Cc: yonghong.song@linux.dev, ihor.solodrai@linux.dev, eddyz87@gmail.com, jolsa@kernel.org, andrii@kernel.org, ast@kernel.org, david.faust@oracle.com, dwarves@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH v2 dwarves 4/5] man-pages: document true_signature btf_feature Message-ID: References: <20260123172650.4062362-1-alan.maguire@oracle.com> <20260123172650.4062362-5-alan.maguire@oracle.com> Precedence: bulk X-Mailing-List: bpf@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: On Mon, Jan 26, 2026 at 10:51:31AM +0000, Alan Maguire wrote: > On 26/01/2026 10:02, Matt Bobrowski wrote: > > On Fri, Jan 23, 2026 at 05:26:49PM +0000, Alan Maguire wrote: > >> Ensure non-default "true_signature" feature is documented in > >> the manual page. > >> > >> Signed-off-by: Alan Maguire > > > > Acked-by: Matt Bobrowski > > > >> --- > >> man-pages/pahole.1 | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/man-pages/pahole.1 b/man-pages/pahole.1 > >> index 3125de3..90a8f45 100644 > >> --- a/man-pages/pahole.1 > >> +++ b/man-pages/pahole.1 > >> @@ -337,6 +337,11 @@ Supported non-standard features (not enabled for 'default') > >> of split BTF with a possibly changed base, storing > >> it in a .BTF.base ELF section. > >> global_var Encode all global variables using BTF_KIND_VAR in BTF. > >> + true_signature Encode functions ensuring that binary-level > >> + (rather than source-level) signatures are used; > > ^ > > within the generated BTF. > > > >> + for gcc these are ".isra.0" and ".costprop.0" > >> + optimized functions > > > > For BTF generation, would there ever be a situation whereby we > > wouldn't want true signature support? I'm just trying to understand > > why this isn't defaulted to true. > > The key reason is the "." in the name for gcc-optimized functions > "function.isra.0" ; older kernels will reject BTF function names with > a "." in them, so we have to guard against new pahole with the feature > enabled by default being run on older kernels. So by having the newer > kernels request the feature only we avoid this. Oh, yes, that makes sense. Once a new pahole version is released with true_signature support available, will you also be looking to update scripts/Makefile.btf and conditionally enable it based on availability?