[PATCH bpf-next 1/2] ftrace: Add HAVE_DYNAMIC_FTRACE_NO_PATCHABLE

Jiri Olsa
2022-08-26T18:50:57Z

From: "Peter Zijlstra (Intel)" <peterz@infradead.org>

x86 will shortly start using -fpatchable-function-entry for purposes
other than ftrace, make sure the __patchable_function_entry section
isn't merged in the mcount_loc section.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/asm-generic/vmlinux.lds.h | 11 ++++++++++-
kernel/trace/Kconfig | 6 ++++++
tools/objtool/check.c | 3 ++-
3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7515a465ec03..13b197ef0d63 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -154,6 +154,14 @@
#define MEM_DISCARD(sec) *(.mem##sec)
#endif

+#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
+#define KEEP_PATCHABLE KEEP(*(__patchable_function_entries))
+#define PATCHABLE_DISCARDS
+#else
+#define KEEP_PATCHABLE
+#define PATCHABLE_DISCARDS *(__patchable_function_entries)
+#endif
+
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
/*
* The ftrace call sites are logged to a section whose name depends on the
@@ -172,7 +180,7 @@
#define MCOUNT_REC() . = ALIGN(8); \
__start_mcount_loc = .; \
KEEP(*(__mcount_loc)) \
- KEEP(*(__patchable_function_entries)) \
+ KEEP_PATCHABLE \
__stop_mcount_loc = .; \
ftrace_stub_graph = ftrace_stub; \
ftrace_ops_list_func = arch_ftrace_ops_list_func;
@@ -1024,6 +1032,7 @@

#define COMMON_DISCARDS \
SANITIZER_DISCARDS \
+ PATCHABLE_DISCARDS \
*(.discard) \
*(.discard.*) \
*(.modinfo) \
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 1052126bdca2..e9e95c790b8e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -51,6 +51,12 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
This allows for use of regs_get_kernel_argument() and
kernel_stack_pointer().

+config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
+ bool
+ help
+ If the architecture generates __patchable_function_entries sections
+ but does not want them included in the ftrace locations.
+
config HAVE_FTRACE_MCOUNT_RECORD
bool
help
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0cec74da7ffe..f23e8d11f6d4 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4110,7 +4110,8 @@ static int validate_ibt(struct objtool_file *file)
!strcmp(sec->name, "__bug_table") ||
!strcmp(sec->name, "__ex_table") ||
!strcmp(sec->name, "__jump_table") ||
- !strcmp(sec->name, "__mcount_loc"))
+ !strcmp(sec->name, "__mcount_loc") ||
+ strstr(sec->name, "__patchable_function_entries"))
continue;

list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
--
2.37.2