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 <[email protected]>
Link:
https://lore.kernel.org/all/[email protected]/
[1]
Suggested-by: Petr Pavlu <[email protected]>
Cc: [email protected]
Signed-off-by: Hao Ge <[email protected]>
---
[...]
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().
