[PATCH 5.10 043/121] gcc-plugins/stackleak: Use noinstr in favor of notrace

Greg Kroah-Hartman
2022-02-21T09:14:08Z

From: Kees Cook <keescook@chromium.org>

[ Upstream commit dcb85f85fa6f142aae1fe86f399d4503d49f2b60 ]

While the stackleak plugin was already using notrace, objtool is now a
bit more picky. Update the notrace uses to noinstr. Silences the
following objtool warnings when building with:

CONFIG_DEBUG_ENTRY=y
CONFIG_STACK_VALIDATION=y
CONFIG_VMLINUX_VALIDATION=y
CONFIG_GCC_PLUGIN_STACKLEAK=y

vmlinux.o: warning: objtool: do_syscall_64()+0x9: call to stackleak_track_stack() leaves .noinstr.text section
vmlinux.o: warning: objtool: do_int80_syscall_32()+0x9: call to stackleak_track_stack() leaves .noinstr.text section
vmlinux.o: warning: objtool: exc_general_protection()+0x22: call to stackleak_track_stack() leaves .noinstr.text section
vmlinux.o: warning: objtool: fixup_bad_iret()+0x20: call to stackleak_track_stack() leaves .noinstr.text section
vmlinux.o: warning: objtool: do_machine_check()+0x27: call to stackleak_track_stack() leaves .noinstr.text section
vmlinux.o: warning: objtool: .text+0x5346e: call to stackleak_erase() leaves .noinstr.text section
vmlinux.o: warning: objtool: .entry.text+0x143: call to stackleak_erase() leaves .noinstr.text section
vmlinux.o: warning: objtool: .entry.text+0x10eb: call to stackleak_erase() leaves .noinstr.text section
vmlinux.o: warning: objtool: .entry.text+0x17f9: call to stackleak_erase() leaves .noinstr.text section

Note that the plugin's addition of calls to stackleak_track_stack() from
noinstr functions is expected to be safe, as it isn't runtime
instrumentation and is self-contained.

Cc: Alexander Popov <alex.popov@linux.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/stackleak.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/stackleak.c b/kernel/stackleak.c
index ce161a8e8d975..dd07239ddff9f 100644
--- a/kernel/stackleak.c
+++ b/kernel/stackleak.c
@@ -48,7 +48,7 @@ int stack_erasing_sysctl(struct ctl_table *table, int write,
#define skip_erasing() false
#endif /* CONFIG_STACKLEAK_RUNTIME_DISABLE */

-asmlinkage void notrace stackleak_erase(void)
+asmlinkage void noinstr stackleak_erase(void)
{
/* It would be nice not to have 'kstack_ptr' and 'boundary' on stack */
unsigned long kstack_ptr = current->lowest_stack;
@@ -102,9 +102,8 @@ asmlinkage void notrace stackleak_erase(void)
/* Reset the 'lowest_stack' value for the next syscall */
current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64;
}
-NOKPROBE_SYMBOL(stackleak_erase);

-void __used __no_caller_saved_registers notrace stackleak_track_stack(void)
+void __used __no_caller_saved_registers noinstr stackleak_track_stack(void)
{
unsigned long sp = current_stack_pointer;

--
2.34.1