Merge: powerpc fixes for out-of-line ftrace stubs and livepatching

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1561

JIRA: https://issues.redhat.com/browse/RHEL-113085

This patch series fixes a couple of bugs in the powerpc64 out-of-line
(OOL) ftrace support for modules, and follows up with a patch to
simplify the module .stubs allocation code.

The first two patches fix bugs introduced by commit eec3796
("powerpc64/ftrace: Move ftrace sequence out of line"). The first,
suggested by Naveen, ensures that a NOP'd ftrace call site has its
ftrace_ops record updated correctly. The second patch corrects a loop in
setup_ftrace_ool_stubs() to ensure all required stubs are reserved, not
just the first. Together, these bugs lead to potential corruption of the
OOL ftrace stubs area for livepatch modules.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

Approved-by: Steve Best <sbest@redhat.com>
Approved-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>
Approved-by: Waiman Long <longman@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

arch/powerpc/include/asm/module.h

@@ -27,6 +27,7 @@ struct ppc_plt_entry {
 struct mod_arch_specific {
 #ifdef __powerpc64__
 	unsigned int stubs_section;	/* Index of stubs section in module */
+	unsigned int stub_count;	/* Number of stubs used */
 #ifdef CONFIG_PPC_KERNEL_PCREL
 	unsigned int got_section;	/* What section is the GOT? */
 	unsigned int pcpu_section;	/* .data..percpu section */

arch/powerpc/kernel/module_64.c

@@ -209,8 +209,7 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 				    char *secstrings,
 				    struct module *me)
 {
-	/* One extra reloc so it's always 0-addr terminated */
-	unsigned long relocs = 1;
+	unsigned long relocs = 0;
 	unsigned i;
 
 	/* Every relocated section... */
@@ -685,7 +684,7 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
 
 	/* Find this stub, or if that fails, the next avail. entry */
 	stubs = (void *)sechdrs[me->arch.stubs_section].sh_addr;
-	for (i = 0; stub_func_addr(stubs[i].funcdata); i++) {
+	for (i = 0; i < me->arch.stub_count; i++) {
 		if (WARN_ON(i >= num_stubs))
 			return 0;
 
@@ -696,6 +695,7 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
 	if (!create_stub(sechdrs, &stubs[i], addr, me, name))
 		return 0;
 
+	me->arch.stub_count++;
 	return (unsigned long)&stubs[i];
 }
 
@@ -1098,29 +1098,19 @@ int module_trampoline_target(struct module *mod, unsigned long addr,
 static int setup_ftrace_ool_stubs(const Elf64_Shdr *sechdrs, unsigned long addr, struct module *me)
 {
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
-	unsigned int i, total_stubs, num_stubs;
+	unsigned int total_stubs, num_stubs;
 	struct ppc64_stub_entry *stub;
 
 	total_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*stub);
 	num_stubs = roundup(me->arch.ool_stub_count * sizeof(struct ftrace_ool_stub),
 			    sizeof(struct ppc64_stub_entry)) / sizeof(struct ppc64_stub_entry);
 
-	/* Find the next available entry */
-	stub = (void *)sechdrs[me->arch.stubs_section].sh_addr;
-	for (i = 0; stub_func_addr(stub[i].funcdata); i++)
-		if (WARN_ON(i >= total_stubs))
-			return -1;
-
-	if (WARN_ON(i + num_stubs > total_stubs))
+	if (WARN_ON(me->arch.stub_count + num_stubs > total_stubs))
 		return -1;
 
-	stub += i;
-	me->arch.ool_stubs = (struct ftrace_ool_stub *)stub;
-
-	/* reserve stubs */
-	for (i = 0; i < num_stubs; i++)
-		if (patch_u32((void *)&stub->funcdata, PPC_RAW_NOP()))
-			return -1;
+	stub = (void *)sechdrs[me->arch.stubs_section].sh_addr;
+	me->arch.ool_stubs = (struct ftrace_ool_stub *)(stub + me->arch.stub_count);
+	me->arch.stub_count += num_stubs;
 #endif
 
 	return 0;

arch/powerpc/kernel/trace/ftrace.c

@@ -490,8 +490,10 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 		return ret;
 
 	/* Set up out-of-line stub */
-	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
-		return ftrace_init_ool_stub(mod, rec);
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
+		ret = ftrace_init_ool_stub(mod, rec);
+		goto out;
+	}
 
 	/* Nop-out the ftrace location */
 	new = ppc_inst(PPC_RAW_NOP());
@@ -522,6 +524,10 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 		return -EINVAL;
 	}
 
+out:
+	if (!ret)
+		ret = ftrace_rec_set_nop_ops(rec);
+
 	return ret;
 }