In order to allow rewriting all direct (tail) calls to ENDBR to go +4, also
generate a tail-call sites section.
This must be different from the .call_sites, because call depth tracking
specifically cares about the CALL instruction, but not JMP instructions.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/vmlinux.lds.S | 9 ++++-
tools/objtool/check.c | 52 +++++++++++++++++++++++++++++---
tools/objtool/include/objtool/objtool.h | 1
tools/objtool/objtool.c | 1
4 files changed, 58 insertions(+), 5 deletions(-)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -285,6 +285,7 @@ SECTIONS
*(.return_sites)
__return_sites_end = .;
}
+#endif
. = ALIGN(8);
.call_sites : AT(ADDR(.call_sites) - LOAD_OFFSET) {
@@ -292,7 +293,13 @@ SECTIONS
*(.call_sites)
__call_sites_end = .;
}
-#endif
+
+ . = ALIGN(8);
+ .tail_call_sites : AT(ADDR(.tail_call_sites) - LOAD_OFFSET) {
+ __tail_call_sites = .;
+ *(.tail_call_sites)
+ __tail_call_sites_end = .;
+ }
#ifdef CONFIG_X86_KERNEL_IBT
. = ALIGN(8);
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -893,7 +893,6 @@ static int create_cfi_sections(struct ob
sec = find_section_by_name(file->elf, ".cfi_sites");
if (sec) {
- INIT_LIST_HEAD(&file->call_list);
WARN("file already has .cfi_sites section, skipping");
return 0;
}
@@ -1018,6 +1017,45 @@ static int create_direct_call_sections(s
return 0;
}
+static int create_direct_tail_call_sections(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct section *sec;
+ int idx;
+
+ sec = find_section_by_name(file->elf, ".tail_call_sites");
+ if (sec) {
+ INIT_LIST_HEAD(&file->tail_call_list);
+ WARN("file already has .tail_call_sites section, skipping");
+ return 0;
+ }
+
+ if (list_empty(&file->tail_call_list))
+ return 0;
+
+ idx = 0;
+ list_for_each_entry(insn, &file->tail_call_list, call_node)
+ idx++;
+
+ sec = elf_create_section_pair(file->elf, ".tail_call_sites",
+ sizeof(unsigned int), idx, idx);
+ if (!sec)
+ return -1;
+
+ idx = 0;
+ list_for_each_entry(insn, &file->tail_call_list, call_node) {
+
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(unsigned int), idx,
+ insn->sec, insn->offset))
+ return -1;
+
+ idx++;
+ }
+
+ return 0;
+}
+
/*
* Warnings shouldn't be reported for ignored functions.
*/
@@ -1417,9 +1455,12 @@ static void annotate_call_site(struct ob
return;
}
- if (insn->type == INSN_CALL && !insn->sec->init &&
- !insn->_call_dest->embedded_insn)
- list_add_tail(&insn->call_node, &file->call_list);
+ if (!insn->sec->init && !insn->_call_dest->embedded_insn) {
+ if (insn->type == INSN_CALL)
+ list_add_tail(&insn->call_node, &file->call_list);
+ else
+ list_add_tail(&insn->call_node, &file->tail_call_list);
+ }
if (!sibling && dead_end_function(file, sym))
insn->dead_end = true;
@@ -4802,6 +4843,9 @@ int check(struct objtool_file *file)
ret = create_direct_call_sections(file);
if (ret < 0)
goto out;
+ ret = create_direct_tail_call_sections(file);
+ if (ret < 0)
+ goto out;
warnings += ret;
}
}
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -28,6 +28,7 @@ struct objtool_file {
struct list_head mcount_loc_list;
struct list_head endbr_list;
struct list_head call_list;
+ struct list_head tail_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.mcount_loc_list);
INIT_LIST_HEAD(&file.endbr_list);
INIT_LIST_HEAD(&file.call_list);
+ INIT_LIST_HEAD(&file.tail_call_list);
file.ignore_unreachables = opts.no_unreachable;
file.hints = false;