From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mout.gmx.net ([212.227.17.20]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h156m-0005Uq-0Z for barebox@lists.infradead.org; Tue, 05 Mar 2019 08:07:29 +0000 References: <20190218075202.10091-1-o.rempel@pengutronix.de> <20190218075202.10091-2-o.rempel@pengutronix.de> <20190304190504.kmazotkohbssz2vn@chr> From: Oleksij Rempel Message-ID: <5cf53330-bfa9-5004-1c13-d60363047312@rempel-privat.de> Date: Tue, 5 Mar 2019 09:07:19 +0100 MIME-Version: 1.0 In-Reply-To: <20190304190504.kmazotkohbssz2vn@chr> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============6553241373811981864==" Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH v1 2/4] MIPS: relocation: add relocation support To: Peter Mamonov , Oleksij Rempel Cc: antonypavlov@gmail.com, barebox@lists.infradead.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --===============6553241373811981864== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="9Lrn7IiwCpqemXVBZco6QeYUjjLLT0D5V" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --9Lrn7IiwCpqemXVBZco6QeYUjjLLT0D5V Content-Type: multipart/mixed; boundary="KK0yelKMQacUyKmKhk2m2AFb93TRGkhIb"; protected-headers="v1" From: Oleksij Rempel To: Peter Mamonov , Oleksij Rempel Cc: antonypavlov@gmail.com, barebox@lists.infradead.org Message-ID: <5cf53330-bfa9-5004-1c13-d60363047312@rempel-privat.de> Subject: Re: [PATCH v1 2/4] MIPS: relocation: add relocation support References: <20190218075202.10091-1-o.rempel@pengutronix.de> <20190218075202.10091-2-o.rempel@pengutronix.de> <20190304190504.kmazotkohbssz2vn@chr> In-Reply-To: <20190304190504.kmazotkohbssz2vn@chr> --KK0yelKMQacUyKmKhk2m2AFb93TRGkhIb Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Am 04.03.19 um 20:05 schrieb Peter Mamonov: > Hi, Oleksij, >=20 > On Mon, Feb 18, 2019 at 08:52:00AM +0100, Oleksij Rempel wrote: >> From: Oleksij Rempel >> >> this patch i a port of following patch from u-boot with some additiona= l >> integration changes and fixes of original code: >> | Subject: [PATCH] MIPS: Stop building position independent code >> | >> | U-Boot has up until now built with -fpic for the MIPS architecture, >> | producing position independent code which uses indirection through a= >> | global offset table, making relocation fairly straightforward as it >> | simply involves patching up GOT entries. >> | >> | Using -fpic does however have some downsides. The biggest of these i= s >> | that generated code is bloated in various ways. For example, functio= n >> | calls are indirected through the GOT & the t9 register: >> | >> | 8f998064 lw t9,-32668(gp) >> | 0320f809 jalr t9 >> | >> | Without -fpic the call is simply: >> | >> | 0f803f01 jal be00fc04 >> | >> | This is more compact & faster (due to the lack of the load & the >> | dependency the jump has on its result). It is also easier to read & >> | debug because the disassembly shows what function is being called, >> | rather than just an offset from gp which would then have to be looke= d up >> | in the ELF to discover the target function. >> | >> | Another disadvantage of -fpic is that each function begins with a >> | sequence to calculate the value of the gp register, for example: >> | >> | 3c1c0004 lui gp,0x4 >> | 279c3384 addiu gp,gp,13188 >> | 0399e021 addu gp,gp,t9 >> | >> | Without using -fpic this sequence no longer appears at the start of = each >> | function, reducing code size considerably. >> | >> | This patch switches U-Boot from building with -fpic to building with= >> | -fno-pic, in order to gain the benefits described above. The cost of= >> | this is an extra step during the build process to extract relocation= >> | data from the ELF & write it into a new .rel section in a compact >> | format, plus the added complexity of dealing with multiple types of >> | relocation rather than the single type that applied to the GOT. The >> | benefit is smaller, cleaner, more debuggable code. The relocate_code= () >> | function is reimplemented in C to handle the new relocation scheme, >> | which also makes it easier to read & debug. >> | >> | Taking maltael_defconfig as an example the size of u-boot.bin built >> | using the Codescape MIPS 2016.05-06 toolchain (gcc 4.9.2, binutils >> | 2.24.90) shrinks from 254KiB to 224KiB. >> | >> | Signed-off-by: Paul Burton >> >> Signed-off-by: Oleksij Rempel >> --- >> >> [...] >> >> diff --git a/arch/mips/Makefile b/arch/mips/Makefile >> index 5fbd51ceee..5eccf18fe4 100644 >> --- a/arch/mips/Makefile >> +++ b/arch/mips/Makefile >> @@ -11,7 +11,7 @@ endif >> =20 >> CPPFLAGS +=3D -D__MIPS__ -fno-strict-aliasing -fno-merge-constants >> =20 >> -cflags-y +=3D -G 0 -mno-abicalls -fno-pic -pipe >> +cflags-y +=3D -G 0 -mno-abicalls -pipe >=20 > The patch you've ported from das u-boot removes `-fpic` flag, yet your = patch=20 > removes `-fno-pic`, i.e. it does the opposite thing. Good point, this part of the change has no influence. With or without thi= s flag, noPIC code is build. I'll put it back to avoid confusion. --=20 Regards, Oleksij --KK0yelKMQacUyKmKhk2m2AFb93TRGkhIb-- --9Lrn7IiwCpqemXVBZco6QeYUjjLLT0D5V Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEpENFL0P3hvQ7p0DDdQOiSHVI77QFAlx+LjcACgkQdQOiSHVI 77SDLAf/XFymrXMGTqkNxT2pF+JxQCjFxHfBnG5hYKOSyuC4M/mVfd0PIR1sCThV anqTnABEfwcTHLwV6UrXmrFF/rBQYuxriHYnrpQkogLMuBsgEeYwnagerI3iMldX NpMJRgC07y0klwXl2yXIUyHbV1Cwz7g5NvkFAOLmNDIQ61yIsL5OEWwiPYW/lfSd VziWGsu48TyUdfMxM+0OGjkT6czx2bZZNezgb3tFFpXHwPi1YWGEu2FKTbcv3kfz wDNDXTCIGJ54ptYLjWMf9oy8+b9BcLC9OS89kVh+iwxdBg1s36FHLVVCmGTqTTbA QFFuyWL3GXqtAxE55j7AFaH1o7kgrA== =Oj4b -----END PGP SIGNATURE----- --9Lrn7IiwCpqemXVBZco6QeYUjjLLT0D5V-- --===============6553241373811981864== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox --===============6553241373811981864==--