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

tip-bot2 for Peter Zijlstra
2022-10-17T14:56:35Z

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@infradead.org>
AuthorDate: Thu, 15 Sep 2022 13:11:09 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
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@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111146.016511961@infradead.org
---
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;