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([2001:af0:8000:1409:193:86:92:181]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-485883927a3sm33609875f8f.11.2026.09.09.04.30.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Sep 2026 04:30:54 -0700 (PDT) Message-ID: <76b5edbb-8231-41d0-9e7b-f965af13c324@suse.com> Date: Wed, 9 Sep 2026 13:30:53 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 3/4] module: introduce SH_ENTSIZE_STANDALONE for separately allocated sections To: Hao Ge Cc: Luis Chamberlain , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Suren Baghdasaryan , Andrew Morton , linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sashiko , stable@vger.kernel.org References: <20260908092412.115953-1-hao.ge@linux.dev> <20260908092412.115953-4-hao.ge@linux.dev> Content-Language: en-US From: Petr Pavlu In-Reply-To: <20260908092412.115953-4-hao.ge@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/8/26 11:24 AM, Hao Ge wrote: > SHF_ALLOC means, per the ELF spec, that a section occupies memory > during process execution. Some module sections occupy memory > outside the regular module layout, for example the percpu section > with its per-CPU allocations. The loader currently excludes such > a section from the layout by clearing its SHF_ALLOC, which > overloads the flag with a loader-internal meaning. > apply_relocations() needs a special case for the section, and > find_sec(".data..percpu") returns different results before and > after layout_and_allocate(). > > Introduce SH_ENTSIZE_STANDALONE to mark sections with a separate > allocation. The percpu section is its first user. layout_sections() > and move_module() skip marked sections, and apply_relocations() goes > back to testing only SHF_ALLOC. Based on a patch by Petr Pavlu [1]. > > .data..percpu keeps SHF_ALLOC, so it would now show up under > /sys/module/*/sections/. The section has one instance per CPU and no > single address to report, and the entry never existed before, so > skip it in add_sect_attrs(). add_notes_attrs() indexes its attrs[] > array and skips it too. No functional change otherwise. > > Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") > Reported-by: Sashiko > Link: https://lore.kernel.org/all/499bb60c-c6e3-43a3-bd92-95a0567ece5e@suse.com/ [1] > Suggested-by: Petr Pavlu > Cc: stable@vger.kernel.org > Signed-off-by: Hao Ge > --- > [...] > diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c > index 0fc11e45df9b..49190deae61e 100644 > --- a/kernel/module/kallsyms.c > +++ b/kernel/module/kallsyms.c > @@ -76,7 +76,7 @@ static char elf_type(const Elf_Sym *sym, const struct load_info *info) > } > > static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs, > - unsigned int shnum, unsigned int pcpundx) > + unsigned int shnum) > { > const Elf_Shdr *sec; > enum mod_mem_type type; > @@ -86,11 +86,6 @@ static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs, > !src->st_name) > return false; > > -#ifdef CONFIG_KALLSYMS_ALL > - if (src->st_shndx == pcpundx) > - return true; > -#endif > - > sec = sechdrs + src->st_shndx; > type = sec->sh_entsize >> SH_ENTSIZE_TYPE_SHIFT; > if (!(sec->sh_flags & SHF_ALLOC) > @@ -131,8 +126,7 @@ void layout_symtab(struct module *mod, struct load_info *info) > /* Compute total space required for the core symbols' strtab. */ > for (ndst = i = 0; i < nsrc; i++) { > if (i == 0 || is_livepatch_module(mod) || > - is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum, > - info->index.pcpu)) { > + is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum)) { > strtab_size += strlen(&info->strtab[src[i].st_name]) + 1; > ndst++; > } > @@ -199,8 +193,7 @@ void add_kallsyms(struct module *mod, const struct load_info *info) > for (ndst = i = 0; i < kallsyms->num_symtab; i++) { > kallsyms->typetab[i] = elf_type(src + i, info); > if (i == 0 || is_livepatch_module(mod) || > - is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum, > - info->index.pcpu)) { > + is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum)) { > ssize_t ret; > > mod->core_kallsyms.typetab[ndst] = FTR These changes in kernel/module/kallsyms.c have a conflict with the series "Ignore local labels and mapping symbols during module load" [1], which is currently queued on modules-next, but it should be straightforward to resolve. > diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c > index 01c65d608873..f64170344e69 100644 > --- a/kernel/module/sysfs.c > +++ b/kernel/module/sysfs.c > @@ -62,6 +62,15 @@ static void free_sect_attrs(struct module_sect_attrs *sect_attrs) > kfree(sect_attrs); > } > > +/* > + * .data..percpu has a separate allocation per CPU and no single > + * address to report. > + */ > +static bool sect_visible(const struct load_info *info, unsigned int i) > +{ > + return !sect_empty(&info->sechdrs[i]) && i != info->index.pcpu; > +} > + > static int add_sect_attrs(struct module *mod, const struct load_info *info) > { > struct module_sect_attrs *sect_attrs; > @@ -72,7 +81,7 @@ static int add_sect_attrs(struct module *mod, const struct load_info *info) > > /* Count loaded sections and allocate structures */ > for (i = 0; i < info->hdr->e_shnum; i++) > - if (!sect_empty(&info->sechdrs[i])) > + if (sect_visible(info, i)) > nloaded++; > sect_attrs = kzalloc_flex(*sect_attrs, attrs, nloaded); > if (!sect_attrs) > @@ -92,7 +101,7 @@ static int add_sect_attrs(struct module *mod, const struct load_info *info) > for (i = 0; i < info->hdr->e_shnum; i++) { > Elf_Shdr *sec = &info->sechdrs[i]; > > - if (sect_empty(sec)) > + if (!sect_visible(info, i)) > continue; > sysfs_bin_attr_init(sattr); > sattr->attr.name = > @@ -181,7 +190,7 @@ static int add_notes_attrs(struct module *mod, const struct load_info *info) > > nattr = ¬es_attrs->attrs[0]; > for (loaded = i = 0; i < info->hdr->e_shnum; ++i) { > - if (sect_empty(&info->sechdrs[i])) > + if (!sect_visible(info, i)) > continue; > if (info->sechdrs[i].sh_type == SHT_NOTE) { > sysfs_bin_attr_init(nattr); add_notes_attrs() has two sect_empty() calls. Both should be changed to sect_visible(). With this fixed, the patch looks ok to me. Feel free to add: Reviewed-by: Petr Pavlu [1] https://lore.kernel.org/linux-modules/20260820125007.22943-1-yangtiezhu@loongson.cn/ -- Thanks, Petr