From d2bf98e6fc2612cbd2fc40f75a1e2c5d60262331 Mon Sep 17 00:00:00 2001 From: "Steven J. Magnani" Date: Fri, 2 Apr 2010 13:29:39 -0500 Subject: [PATCH] microblaze: Fix ftrace_update_ftrace_func panic The Microblaze dynamic ftrace code assumes a call ordering that is not met in all scenarios. Specifically, executing a command similar to: echo 105 > /sys/kernel/debug/tracing/set_ftrace_pid before any other tracing-related commands results in a kernel panic: BUG: failure at arch/microblaze/kernel/ftrace.c:198/ftrace_update_ftrace_func()! Recoding ftrace_update_ftrace_func() to use &ftrace_caller directly eliminates the need to capture its address elsewhere (and thus rely on a particular call sequence). Signed-off-by: Steven J. Magnani Signed-off-by: Michal Simek --- arch/microblaze/kernel/ftrace.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/arch/microblaze/kernel/ftrace.c b/arch/microblaze/kernel/ftrace.c index 388b31ca65a1..515feb404555 100644 --- a/arch/microblaze/kernel/ftrace.c +++ b/arch/microblaze/kernel/ftrace.c @@ -151,13 +151,10 @@ int ftrace_make_nop(struct module *mod, return ret; } -static int ret_addr; /* initialized as 0 by default */ - /* I believe that first is called ftrace_make_nop before this function */ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { int ret; - ret_addr = addr; /* saving where the barrier jump is */ pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n", __func__, (unsigned int)addr, (unsigned int)rec->ip, imm); ret = ftrace_modify_code(rec->ip, imm); @@ -194,12 +191,9 @@ int ftrace_update_ftrace_func(ftrace_func_t func) ret = ftrace_modify_code(ip, upper); ret += ftrace_modify_code(ip + 4, lower); - /* We just need to remove the rtsd r15, 8 by NOP */ - BUG_ON(!ret_addr); - if (ret_addr) - ret += ftrace_modify_code(ret_addr, MICROBLAZE_NOP); - else - ret = 1; /* fault */ + /* We just need to replace the rtsd r15, 8 with NOP */ + ret += ftrace_modify_code((unsigned long)&ftrace_caller, + MICROBLAZE_NOP); /* All changes are done - lets do caches consistent */ flush_icache(); -- 2.20.1