Re: [PATCH v4 06/15] ftrace: Use an opaque type for functions not callable from C
From: Josh Poimboeuf <hidden>
Date: 2021-10-06 03:29:54
Also in:
linux-hardening, lkml
On Thu, Sep 30, 2021 at 11:05:22AM -0700, Sami Tolvanen wrote:
quoted hunk ↗ jump to hunk
With CONFIG_CFI_CLANG, the compiler changes function references to point to the CFI jump table. As ftrace_call, ftrace_regs_call, and mcount_call are not called from C, use DECLARE_ASM_FUNC_SYMBOL to declare them. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- include/linux/ftrace.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 832e65f06754..67de28464aeb 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h@@ -578,9 +578,10 @@ extern void ftrace_replace_code(int enable); extern int ftrace_update_ftrace_func(ftrace_func_t func); extern void ftrace_caller(void); extern void ftrace_regs_caller(void); -extern void ftrace_call(void); -extern void ftrace_regs_call(void); -extern void mcount_call(void); + +DECLARE_ASM_FUNC_SYMBOL(ftrace_call); +DECLARE_ASM_FUNC_SYMBOL(ftrace_regs_call); +DECLARE_ASM_FUNC_SYMBOL(mcount_call);
I'm thinking DECLARE_ASM_FUNC_SYMBOL needs a better name. It's not clear from reading it why some asm symbols need the macro and others don't. I guess it means "an asm text symbol which isn't callable from C code (not including alternatives)"? DECLARE_UNCALLED_SYMBOL() maybe? -- Josh