[PATCH 3/4] powerpc: ftrace: Use create_branch() and cope with errors
From: Michael Ellerman <hidden>
Date: 2008-07-17 07:21:32
Subsystem:
function hooks (ftrace), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Steven Rostedt, Masami Hiramatsu, Madhavan Srinivasan, Linus Torvalds
Use create_branch() rather than doing it by hand. It's possible that we are unable to create a branch to the address, if it's too far away, in which case just return a nop. This will break the tracing, but shouldn't crash the kernel at least. Signed-off-by: Michael Ellerman <redacted> --- arch/powerpc/kernel/ftrace.c | 20 ++++++++------------ 1 files changed, 8 insertions(+), 12 deletions(-)
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 1d6f174..49a2049 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c@@ -19,11 +19,6 @@ #include <asm/ftrace.h> -static unsigned int notrace ftrace_calc_offset(long ip, long addr) -{ - return (int)(addr - ip); -} - notrace unsigned char *ftrace_nop_replace(void) { static unsigned int ftrace_nop = PPC_NOP_INSTR;
@@ -35,16 +30,17 @@ notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) { static unsigned int op; - /* - * It would be nice to just use create_function_call, but that will - * update the code itself. Here we need to just return the - * instruction that is going to be modified, without modifying the - * code. - */ addr = ppc_function_entry((void *)addr); /* Set to "bl addr" */ - op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc); + op = create_branch((unsigned int *)ip, addr, BRANCH_SET_LINK); + + /* + * This routine is not allowed to fail, but create_branch() can. + * In that case, just return nop and cross our fingers. + */ + if (!op) + return ftrace_nop_replace(); /* * No locking needed, this must be called via kstop_machine
--
1.5.5