[tip: x86/core] objtool: Add .call_sites section

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     00abd38408127a57861698a8bffba65849de6bbd
Gitweb:        https://git.kernel.org/tip/00abd38408127a57861698a8bffba65849de6bbd
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Thu, 15 Sep 2022 13:11:09 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 17 Oct 2022 16:41:07 +02:00

objtool: Add .call_sites section

In preparation for call depth tracking provide a section which collects all
direct calls.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220915111146.016511961@xxxxxxxxxxxxx
---
 arch/x86/kernel/vmlinux.lds.S           |  7 +++-
 tools/objtool/check.c                   | 51 ++++++++++++++++++++++++-
 tools/objtool/include/objtool/objtool.h |  1 +-
 tools/objtool/objtool.c                 |  1 +-
 4 files changed, 60 insertions(+)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 0e9fc08..b69df9e 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -291,6 +291,13 @@ SECTIONS
 		*(.return_sites)
 		__return_sites_end = .;
 	}
+
+	. = ALIGN(8);
+	.call_sites : AT(ADDR(.call_sites) - LOAD_OFFSET) {
+		__call_sites = .;
+		*(.call_sites)
+		__call_sites_end = .;
+	}
 #endif
 
 #ifdef CONFIG_X86_KERNEL_IBT
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index bb7c819..f578e03 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -902,6 +902,49 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 	return 0;
 }
 
+static int create_direct_call_sections(struct objtool_file *file)
+{
+	struct instruction *insn;
+	struct section *sec;
+	unsigned int *loc;
+	int idx;
+
+	sec = find_section_by_name(file->elf, ".call_sites");
+	if (sec) {
+		INIT_LIST_HEAD(&file->call_list);
+		WARN("file already has .call_sites section, skipping");
+		return 0;
+	}
+
+	if (list_empty(&file->call_list))
+		return 0;
+
+	idx = 0;
+	list_for_each_entry(insn, &file->call_list, call_node)
+		idx++;
+
+	sec = elf_create_section(file->elf, ".call_sites", 0, sizeof(unsigned int), idx);
+	if (!sec)
+		return -1;
+
+	idx = 0;
+	list_for_each_entry(insn, &file->call_list, call_node) {
+
+		loc = (unsigned int *)sec->data->d_buf + idx;
+		memset(loc, 0, sizeof(unsigned int));
+
+		if (elf_add_reloc_to_insn(file->elf, sec,
+					  idx * sizeof(unsigned int),
+					  R_X86_64_PC32,
+					  insn->sec, insn->offset))
+			return -1;
+
+		idx++;
+	}
+
+	return 0;
+}
+
 /*
  * Warnings shouldn't be reported for ignored functions.
  */
@@ -1279,6 +1322,9 @@ static void annotate_call_site(struct objtool_file *file,
 		return;
 	}
 
+	if (insn->type == INSN_CALL && !insn->sec->init)
+		list_add_tail(&insn->call_node, &file->call_list);
+
 	if (!sibling && dead_end_function(file, sym))
 		insn->dead_end = true;
 }
@@ -4305,6 +4351,11 @@ int check(struct objtool_file *file)
 		if (ret < 0)
 			goto out;
 		warnings += ret;
+
+		ret = create_direct_call_sections(file);
+		if (ret < 0)
+			goto out;
+		warnings += ret;
 	}
 
 	if (opts.mcount) {
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 7f2d1b0..6b40977 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -28,6 +28,7 @@ struct objtool_file {
 	struct list_head static_call_list;
 	struct list_head mcount_loc_list;
 	struct list_head endbr_list;
+	struct list_head call_list;
 	bool ignore_unreachables, hints, rodata;
 
 	unsigned int nr_endbr;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index a7ecc32..6affd80 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -106,6 +106,7 @@ struct objtool_file *objtool_open_read(const char *_objname)
 	INIT_LIST_HEAD(&file.static_call_list);
 	INIT_LIST_HEAD(&file.mcount_loc_list);
 	INIT_LIST_HEAD(&file.endbr_list);
+	INIT_LIST_HEAD(&file.call_list);
 	file.ignore_unreachables = opts.no_unreachable;
 	file.hints = false;