From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Mon, 05 Jan 2026 14:12:06 +0100 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1vckNR-001Wx0-3C for lore@lore.pengutronix.de; Mon, 05 Jan 2026 14:12:06 +0100 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1vckNR-0002zq-9J for lore@pengutronix.de; Mon, 05 Jan 2026 14:12:05 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=BJXktaIIObdLX9RKhNcYvUzAeaWWaK7hTimpC2G8EVg=; b=0nSwtJMfdCTa7XRSJRwUGaRXX0 TsZDLBiFiHTn2m1M3Pa5zy/RmTf99mqGvAxkyPyKXBsLgTaBOT2RjfRCvEohIj9e4z9fA017ugU8O CXoKosPfaHZbnmql6E31ND5fhu6L+GrlVjhEgkW91e+a9NnMDTThQBWBqSRgQRGFymsg6elyD869X 8NynX0odCHi9X1q3no6LtTPzcGn8PcLOesviiIm1Ug0xnEqVwWJPGH1sX2KMLcqF/TTE31gk+dPZ9 0QRPWbdJDLbco/IqEPTBOFcwhLg3vYCbMLfz+N8pdHINW/wgfHGf0KWjtLGEd5IGsQ3kLN3E6Uy0a isNmJ+SQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vckMt-0000000BPBf-47NX; Mon, 05 Jan 2026 13:11:31 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vckMs-0000000BPAj-1hLb for barebox@lists.infradead.org; Mon, 05 Jan 2026 13:11:31 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1vckMq-0002v5-OZ; Mon, 05 Jan 2026 14:11:28 +0100 Message-ID: <1d0e01f8-a1d7-4c8c-982a-be21f9dcb67b@pengutronix.de> Date: Mon, 5 Jan 2026 14:11:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer , BAREBOX Cc: "Claude Sonnet 4.5" References: <20260105-pbl-load-elf-v1-0-e97853f98232@pengutronix.de> <20260105-pbl-load-elf-v1-14-e97853f98232@pengutronix.de> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: <20260105-pbl-load-elf-v1-14-e97853f98232@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260105_051130_443991_628EB733 X-CRM114-Status: GOOD ( 20.48 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.0 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 14/19] ARM: linker script: create separate PT_LOAD segments for text, rodata, and data X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 1/5/26 12:26 PM, Sascha Hauer wrote: > Fix the linker scripts to generate three distinct PT_LOAD segments with > correct permissions instead of combining .rodata with .data. > > Before this fix, the linker auto-generated only two PT_LOAD segments: > 1. Text segment (PF_R|PF_X) > 2. Data segment (PF_R|PF_W) - containing .rodata, .data, .bss, etc. Did it though? Why did we get the RWX linker warnings then? > This caused .rodata to be mapped with write permissions when > pbl_mmu_setup_from_elf() set up MMU permissions based on ELF segments, > defeating the W^X protection that commit d9ccb0cf14 intended to provide. What commit hash is this? > With explicit PHDRS directives, we now generate three segments: > 1. text segment (PF_R|PF_X): .text and related code sections > 2. rodata segment (PF_R): .rodata and unwind tables > 3. data segment (PF_R|PF_W): .data, .bss, and related sections Not directly related, but this is as good a place as any to ask the question: How is zero-padding implemented? If the file size is shorter than the memory size, the loader is supposed to zero-fill, which is used for BSS zeroing for example. Now if you load the ELF in place, we can't obviously zero-fill. This is fine, but we should have a check somewhere to make absolutely sure that we don't end up with too short segments. > -#define BAREBOX_RELOCATION_TABLE \ > - .rel_dyn_start : { *(.__rel_dyn_start) } \ > - .BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) } \ > - .rel_dyn_end : { *(.__rel_dyn_end) } \ > - .__dynsym_start : { *(.__dynsym_start) } \ > - .dynsym : { *(.dynsym) } \ > - .__dynsym_end : { *(.__dynsym_end) } > +#define BAREBOX_RELOCATION_TABLE(PHDR) \ > + .rel_dyn_start : { *(.__rel_dyn_start) } PHDR \ > + .BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) } PHDR \ > + .rel_dyn_end : { *(.__rel_dyn_end) } PHDR \ > + .__dynsym_start : { *(.__dynsym_start) } PHDR \ > + .dynsym : { *(.dynsym) } PHDR \ > + .__dynsym_end : { *(.__dynsym_end) } PHDR Quoting https://www.sourceware.org/binutils/docs/ld/Output-Section-Phdr.html: If a section is assigned to one or more segments, then all subsequent allocated sections will be assigned to those segments as well, unless they use an explicitly :phdr modifier. You can use :NONE to tell the linker to not put the section in any segment at all. This whole hunk is thus unnecessary as it follows the data section. > +PHDRS > +{ > + text PT_LOAD FLAGS(5); /* PF_R | PF_X */ > + rodata PT_LOAD FLAGS(4); /* PF_R */ > + data PT_LOAD FLAGS(6); /* PF_R | PF_W */ > + dynamic PT_DYNAMIC FLAGS(6); /* PF_R | PF_W */ I believe we don't need PF_W for PT_DYNAMIC. You could move it one up to merge with rodata. > +} > + > SECTIONS > { > . = 0x0; > - .image_start : { *(.__image_start) } > + .image_start : { *(.__image_start) } :text > > . = ALIGN(4); > > - ._text : { *(._text) } > + ._text : { *(._text) } :text > .text : > { > _stext = .; > @@ -31,7 +40,7 @@ SECTIONS > KEEP(*(.text_inplace_exceptions*)) > __inplace_exceptions_stop = .; > *(.text*) > - } > + } :text > BAREBOX_BARE_INIT_SIZE > > . = ALIGN(4096); > @@ -39,7 +48,7 @@ SECTIONS > .rodata : { > *(.rodata*) > RO_DATA_SECTION > - } > + } :rodata > > #ifdef CONFIG_ARM_UNWIND > /* > @@ -50,12 +59,12 @@ SECTIONS > __start_unwind_idx = .; > *(.ARM.exidx*) > __stop_unwind_idx = .; > - } > + } :rodata > .ARM.unwind_tab : { > __start_unwind_tab = .; > *(.ARM.extab*) > __stop_unwind_tab = .; > - } > + } :rodata > #endif > . = ALIGN(4096); > __end_rodata = .; > @@ -65,19 +74,21 @@ SECTIONS > . = ALIGN(4); > .data : { *(.data*) > CONSTRUCTORS > - } > + } :data > + > + .dynamic : { *(.dynamic) } :data :dynamic As mentioned above. s/:data/:rodata/ and move up? > > . = .; > > - BAREBOX_RELOCATION_TABLE > + BAREBOX_RELOCATION_TABLE(:data) > > _edata = .; > - .image_end : { *(.__image_end) } > + .image_end : { *(.__image_end) } :data > > . = ALIGN(4); > - .__bss_start : { *(.__bss_start) } > - .bss : { *(.bss*) } > - .__bss_stop : { *(.__bss_stop) } > + .__bss_start : { *(.__bss_start) } :data > + .bss : { *(.bss*) } :data > + .__bss_stop : { *(.__bss_stop) } :data Side-effect of having the decompressor take care of zeroing BSS is a big size increase for CONFIG_IMAGE_COMPRESSION_NONE. I think that's acceptable, but it's worth a comment here why we don't have a separate BSS segment (or make bss NOALLOC). FYI, I have patches to get rid of MAX_BSS_SIZE on top of PBL ELF loader support, which I will submit once this support is merged. Cheers, Ahmad -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |