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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-395c82c23ffsm1498503f8f.22.2025.03.13.02.38.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Mar 2025 02:38:39 -0700 (PDT) Date: Thu, 13 Mar 2025 09:38:38 +0000 From: David Laight To: Geert Uytterhoeven Cc: Uros Bizjak , John Paul Adrian Glaubitz , Artur Rojek , Yoshinori Sato , Rich Felker , Daniel Lezcano , Thomas Gleixner , Geert Uytterhoeven , "D . Jeff Dionne" , Rob Landley , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] sh: align .bss section padding to 8-byte boundary Message-ID: <20250313093838.10749599@pumpkin> In-Reply-To: References: <20250216175545.35079-1-contact@artur-rojek.eu> <20250216175545.35079-2-contact@artur-rojek.eu> <5365422a9715376c76a89e255c978fc39064e243.camel@physik.fu-berlin.de> <433bc8a0732bf8a63c64c4bf0e6ad4a7@artur-rojek.eu> <967e29681c8bc39edfdd9c645d943f17d341c2ae.camel@physik.fu-berlin.de> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-sh@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 12 Mar 2025 10:47:00 +0100 Geert Uytterhoeven wrote: > Hi Uros, >=20 > On Wed, 12 Mar 2025 at 09:32, Uros Bizjak wrote: > > On Wed, Mar 12, 2025 at 9:22=E2=80=AFAM John Paul Adrian Glaubitz > > wrote: =20 .... > > > OK. FWIW, do you understand what SBSS is for? I couldn't find any exp= lanation > > > for it. =20 > > > > Small BSS section. The compiler can put data objects under a certain > > size threshold to the .sbss section. Looking at GCC sh config, sh does > > not use this section. =20 The .sbss (and .sdata) sections are used by some architectures (eg Nios2) for data that can be accessed using a 16bit offset from a fixed register. (Although using the register as global register variable generates better c= ode.) Historically they may have been used for data at the top/bottom of the addresses space (for the same reason). There is no reason to just use it for 'small' (eg 8 bytes or less) data, that is just some empirical default. I guess they could also be used on cpu like the strongarm for memory that used the 'small data cache' (useful for screen buffer memory!). David