Hi Suren Thanks for your review.
On 2026/8/15 14:21, Suren Baghdasaryan wrote: > On Thu, Aug 13, 2026 at 2:34 AM Hao Ge <[email protected]> wrote: >> codetag_needs_module_section() is called twice per codetag section, once >> in layout_sections() and once in move_module(), and both depend on >> mem_profiling_support, which changes without a lock. If profiling is >> disabled between the two calls, layout excludes the section (offset 0) >> while move copies it as normal memory to offset 0: >> >> CPU0 (insmod A) CPU1 (insmod B) >> ---------------- ---------------- >> layout_sections() >> needs_section_mem() == true >> sh_entsize: type, offset = 0 >> reserve_module_tags() overflows >> shutdown_mem_profiling() >> mem_profiling_support = false >> move_module() >> needs_section_mem() == false >> offset = sh_entsize & MASK = 0 >> memcpy(mod->mem[type].base + 0, ...) >> -> overwrites the first section there >> >> Record the decision in layout_sections() in sh_entsize using a >> MOD_MEM_CODETAG type, and have move_module() use that instead of asking >> again. >> >> reserve_module_tags() returns -EAGAIN if profiling was disabled after >> layout, so the loader retries and places the section as normal memory. >> >> Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag >> compression") >> Signed-off-by: Hao Ge <[email protected]> >> --- >> include/linux/module.h | 11 +++++++++++ >> kernel/module/main.c | 17 ++++++----------- >> mm/alloc_tag.c | 8 ++++++++ >> 3 files changed, 25 insertions(+), 11 deletions(-) >> >> diff --git a/include/linux/module.h b/include/linux/module.h >> index 7566815fabbe..a02016528e1d 100644 >> --- a/include/linux/module.h >> +++ b/include/linux/module.h >> @@ -328,6 +328,17 @@ enum mod_mem_type { >> MOD_INVALID = -1, >> }; >> >> +/* >> + * If CONFIG_CODE_TAGGING is on, modules get a .codetag section. >> + * codetag_needs_module_section() says where it goes: the usual >> + * mod->mem[], or off to the codetag region. >> + * >> + * Mark the codetag-region ones with MOD_MEM_NUM_TYPES. >> + * It's just past the real types, so it doesn't index into mod->mem[] >> + * and for_each_mod_mem_type() skips it. >> + */ >> +#define MOD_MEM_CODETAG MOD_MEM_NUM_TYPES > Ok, it feels a bit hacky but it's probably the simplest way to mark > codetag regions. > Yeah, it's not the prettiest — that's part of why I sent this series as an RFC. Actually, I was wondering whether we could turn this into a generic marker which means the section does not live in mod->mem[] but in a region managed by its owning subsystem, codetag being the first user. Of course, we still need to consult the module subsystem experts about this. >> + >> #define mod_mem_type_is_init(type) \ >> ((type) == MOD_INIT_TEXT || \ >> (type) == MOD_INIT_DATA || \ >> diff --git a/kernel/module/main.c b/kernel/module/main.c >> index ed26f167be84..2337bf604f58 100644 >> --- a/kernel/module/main.c >> +++ b/kernel/module/main.c >> @@ -1728,11 +1728,8 @@ static void __layout_sections(struct module *mod, >> struct load_info *info, bool i >> * preallocated contiguous memory. >> */ >> if (codetag_needs_module_section(mod, sname, >> s->sh_size)) { >> - /* >> - * s->sh_entsize won't be used but populate >> the >> - * type field to avoid confusion. >> - */ >> - s->sh_entsize = ((unsigned long)(type) & >> SH_ENTSIZE_TYPE_MASK) >> + s->sh_entsize = ((unsigned >> long)MOD_MEM_CODETAG >> + & SH_ENTSIZE_TYPE_MASK) >> << SH_ENTSIZE_TYPE_SHIFT; >> continue; >> } >> @@ -2815,11 +2812,10 @@ static int move_module(struct module *mod, struct >> load_info *info) >> continue; >> >> sname = info->secstrings + shdr->sh_name; >> - /* >> - * Load codetag sections separately as they might still be >> used >> - * after module unload. >> - */ >> - if (codetag_needs_module_section(mod, sname, shdr->sh_size)) >> { >> + >> + enum mod_mem_type type = shdr->sh_entsize >> >> SH_ENTSIZE_TYPE_SHIFT; >> + >> + if (type == MOD_MEM_CODETAG) { >> dest = codetag_alloc_module_section(mod, sname, >> shdr->sh_size, >> arch_mod_section_prepend(mod, i), >> shdr->sh_addralign); >> if (WARN_ON(!dest)) { >> @@ -2832,7 +2828,6 @@ static int move_module(struct module *mod, struct >> load_info *info) >> } >> codetag_section_found = true; >> } else { >> - enum mod_mem_type type = shdr->sh_entsize >> >> SH_ENTSIZE_TYPE_SHIFT; >> unsigned long offset = shdr->sh_entsize & >> SH_ENTSIZE_OFFSET_MASK; >> >> dest = mod->mem[type].base + offset; >> diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c >> index 461fa87fbb0b..7481180dadd2 100644 >> --- a/mm/alloc_tag.c >> +++ b/mm/alloc_tag.c >> @@ -893,6 +893,14 @@ static void *reserve_module_tags(struct module *mod, >> unsigned long size, >> if (size < sizeof(struct alloc_tag)) >> return ERR_PTR(-EINVAL); >> >> + /* >> + * Profiling may have been disabled by a concurrent module load. >> + * Return -EAGAIN so the loader retries with profiling off, laying >> + * the section out as ordinary module memory. >> + */ >> + if (!mem_profiling_support) >> + return ERR_PTR(-EAGAIN); > I think this requires your patch [1] from another patchset to work > correctly, correct? If so, I would suggest sending this patch as part > of that patchset since there is a dependency. > Right, this hunk needs the retry from [1] to work. I'll drop this patch from this series and send it as part of that patchset instead. I'll wait until we sort out the plan for [1] with Petr before pushing this. Feedback from the module‑subsystem experts on this patch is most welcome. > [1] https://lore.kernel.org/all/[email protected]/ > > >> + >> /* >> * align is always power of 2, so we can use IS_ALIGNED and ALIGN. >> * align 0 or 1 means no alignment, to simplify set to 1. >> -- >> 2.25.1
