Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.

1 files changed, 168 insertions, 0 deletions

diff --git a/tools/objtool/klp-post-link.c b/tools/objtool/klp-post-link.c
new file mode 100644
index 000000000..c013e3995
--- /dev/null
+++ b/tools/objtool/klp-post-link.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Read the intermediate KLP reloc/symbol representations created by klp diff
+ * and convert them to the proper format required by livepatch.  This needs to
+ * run last to avoid linker wreckage.  Linkers don't tend to handle the "two
+ * rela sections for a single base section" case very well, nor do they like
+ * SHN_LIVEPATCH.
+ *
+ * This is the final tool in the livepatch module generation pipeline:
+ *
+ *   kernel builds -> objtool klp diff -> module link -> objtool klp post-link
+ */
+
+#include <fcntl.h>
+#include <gelf.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+#include <objtool/klp.h>
+#include <objtool/util.h>
+#include <linux/livepatch_external.h>
+
+static int fix_klp_relocs(struct elf *elf)
+{
+	struct section *symtab, *klp_relocs;
+
+	klp_relocs = find_section_by_name(elf, KLP_RELOCS_SEC);
+	if (!klp_relocs)
+		return 0;
+
+	symtab = find_section_by_name(elf, ".symtab");
+	if (!symtab) {
+		ERROR("missing .symtab");
+		return -1;
+	}
+
+	for (int i = 0; i < sec_size(klp_relocs) / sizeof(struct klp_reloc); i++) {
+		struct klp_reloc *klp_reloc;
+		unsigned long klp_reloc_off;
+		struct section *sec, *tmp, *klp_rsec;
+		unsigned long offset;
+		struct reloc *reloc;
+		char sym_modname[64];
+		char rsec_name[SEC_NAME_LEN];
+		u64 addend;
+		struct symbol *sym, *klp_sym;
+
+		klp_reloc_off = i * sizeof(*klp_reloc);
+		klp_reloc = klp_relocs->data->d_buf + klp_reloc_off;
+
+		/*
+		 * Read __klp_relocs[i]:
+		 */
+
+		/* klp_reloc.sec_offset */
+		reloc = find_reloc_by_dest(elf, klp_relocs,
+					   klp_reloc_off + offsetof(struct klp_reloc, offset));
+		if (!reloc) {
+			ERROR("malformed " KLP_RELOCS_SEC " section");
+			return -1;
+		}
+
+		sec = reloc->sym->sec;
+		offset = reloc_addend(reloc);
+
+		/* klp_reloc.sym */
+		reloc = find_reloc_by_dest(elf, klp_relocs,
+					   klp_reloc_off + offsetof(struct klp_reloc, sym));
+		if (!reloc) {
+			ERROR("malformed " KLP_RELOCS_SEC " section");
+			return -1;
+		}
+
+		klp_sym = reloc->sym;
+		addend = reloc_addend(reloc);
+
+		/* symbol format: .klp.sym.modname.sym_name,sympos */
+		if (sscanf(klp_sym->name + strlen(KLP_SYM_PREFIX), "%55[^.]", sym_modname) != 1)
+			ERROR("can't find modname in klp symbol '%s'", klp_sym->name);
+
+		/*
+		 * Create the KLP rela:
+		 */
+
+		/* section format: .klp.rela.sec_objname.section_name */
+		if (snprintf_check(rsec_name, SEC_NAME_LEN,
+				   KLP_RELOC_SEC_PREFIX "%s.%s",
+				   sym_modname, sec->name))
+			return -1;
+
+		klp_rsec = find_section_by_name(elf, rsec_name);
+		if (!klp_rsec) {
+			klp_rsec = elf_create_section(elf, rsec_name, 0,
+						      elf_rela_size(elf),
+						      SHT_RELA, elf_addr_size(elf),
+						      SHF_ALLOC | SHF_INFO_LINK | SHF_RELA_LIVEPATCH);
+			if (!klp_rsec)
+				return -1;
+
+			klp_rsec->sh.sh_link = symtab->idx;
+			klp_rsec->sh.sh_info = sec->idx;
+			klp_rsec->base = sec;
+		}
+
+		tmp = sec->rsec;
+		sec->rsec = klp_rsec;
+		if (!elf_create_reloc(elf, sec, offset, klp_sym, addend, klp_reloc->type))
+			return -1;
+		sec->rsec = tmp;
+
+		/*
+		 * Fix up the corresponding KLP symbol:
+		 */
+
+		klp_sym->sym.st_shndx = SHN_LIVEPATCH;
+		if (!gelf_update_sym(symtab->data, klp_sym->idx, &klp_sym->sym)) {
+			ERROR_ELF("gelf_update_sym");
+			return -1;
+		}
+
+		/*
+		 * Disable the original non-KLP reloc by converting it to R_*_NONE:
+		 */
+
+		reloc = find_reloc_by_dest(elf, sec, offset);
+		sym = reloc->sym;
+		sym->sym.st_shndx = SHN_LIVEPATCH;
+		set_reloc_type(elf, reloc, 0);
+		if (!gelf_update_sym(symtab->data, sym->idx, &sym->sym)) {
+			ERROR_ELF("gelf_update_sym");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * This runs on the livepatch module after all other linking has been done.  It
+ * converts the intermediate __klp_relocs section into proper KLP relocs to be
+ * processed by livepatch.  This needs to run last to avoid linker wreckage.
+ * Linkers don't tend to handle the "two rela sections for a single base
+ * section" case very well, nor do they appreciate SHN_LIVEPATCH.
+ */
+int cmd_klp_post_link(int argc, const char **argv)
+{
+	struct elf *elf;
+
+	argc--;
+	argv++;
+
+	if (argc != 1) {
+		fprintf(stderr, "%d\n", argc);
+		fprintf(stderr, "usage: objtool link <file.ko>\n");
+		return -1;
+	}
+
+	elf = elf_open_read(argv[0], O_RDWR);
+	if (!elf)
+		return -1;
+
+	if (fix_klp_relocs(elf))
+		return -1;
+
+	if (elf_write(elf))
+		return -1;
+
+	return elf_close(elf);
+}