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Wed, 09 Sep 2026 12:48:01 +0000 X-Mizu-Trace-ID: cd2dbaa2e085f090 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Wed, 9 Sep 2026 20:47:52 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 3/4] module: introduce SH_ENTSIZE_STANDALONE for separately allocated sections To: Petr Pavlu 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> <76b5edbb-8231-41d0-9e7b-f965af13c324@suse.com> Content-Language: en-US From: Hao Ge In-Reply-To: <76b5edbb-8231-41d0-9e7b-f965af13c324@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 29AFE180005 X-Stat-Signature: ct6gn335zic945rdn1t1zzkux7a5jnon X-Rspam-User: X-HE-Tag: 1788958082-557418 X-HE-Meta: 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 GkED9e0T wVa+6oQTehUwvVkII2wJCC9PWK4RbfJy5BXEXgLKIYlspSnJdB7YhEhXnMIgaO0QFApV9U7Ld02GpU71DSldKM3D3MLbu3j4SeUOa1wTCYa85YrMFDM27gwnY1kMBFc1rEfE8AFuQSY+F8sCXjwknU0ryGrCy0n5/NZ7KRp0AyXg8OOQwcciqc5+XvRc3dIaiclQZYcBWYBtCS0ZXssYCSMCxFYL1rL/bTURyNQDGHcA1Q97zhxSvYXoIIqr187WlJoxxcz+S1k1KhQ8//BHk8mxDhofiaMB+Q5en9ZRgsDm54kd7NJtifsvTBC0B6rGjzdEAxokXsEheRmauYlZby75Uxq8GD4x5Sg08E1+co62uI3JufOwbElKEeR/HgjOq4LbPOW9h6874ReiMYTJ3uPDz0Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Petr On 9/9/26 19:30, Petr Pavlu wrote: > 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(). I kept this part unmodified to preserve the loop's original intent. This loop counts SHT_NOTE sections. SHT_NOTE refers to ELF note sections, which hold non-executable metadata such as build ID and ABI info. I wonder if we could keep the current implementation. As noted in the comment above, the top part counts SHT_NOTE sections and allocates structures, while the lower logic handles control of node attributes. WDYT? Thanks Best Regards Hao > > 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/ >