[PATCH v3 30/59] objtool: Add .call_sites section

Peter Zijlstra
2022-09-15T11:43:56Z

From: Peter Zijlstra <peterz@infradead.org>

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>
---
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(+)

--- 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
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -898,6 +898,49 @@ static int create_mcount_loc_sections(st
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.
*/
@@ -1252,6 +1295,9 @@ static void annotate_call_site(struct ob
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;
}
@@ -4274,6 +4320,11 @@ 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) {
--- 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;
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -106,6 +106,7 @@ struct objtool_file *objtool_open_read(c
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;