3.2.93-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: "Naveen N. Rao" <[email protected]> commit a9f8553e935f26cb5447f67e280946b0923cd2dc upstream. This fixes a crash when function_graph and jprobes are used together. This is essentially commit 237d28db036e ("ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing"), but for powerpc. Jprobes breaks function_graph tracing since the jprobe hook needs to use jprobe_return(), which never returns back to the hook, but instead to the original jprobe'd function. The solution is to momentarily pause function_graph tracing before invoking the jprobe hook and re-enable it when returning back to the original jprobe'd function. Fixes: 6794c78243bf ("powerpc64: port of the function graph tracer") Signed-off-by: Naveen N. Rao <[email protected]> Acked-by: Masami Hiramatsu <[email protected]> Acked-by: Steven Rostedt (VMware) <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> [bwh: Backported to 3.2: include <linux/ftrace.h>, which apparently gets included indirectly upstream] Signed-off-by: Ben Hutchings <[email protected]> --- --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -32,6 +32,7 @@ #include <linux/module.h> #include <linux/kdebug.h> #include <linux/slab.h> +#include <linux/ftrace.h> #include <asm/cacheflush.h> #include <asm/sstep.h> #include <asm/uaccess.h> @@ -530,6 +531,15 @@ int __kprobes setjmp_pre_handler(struct regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc); #endif + /* + * jprobes use jprobe_return() which skips the normal return + * path of the function, and this messes up the accounting of the + * function graph tracer. + * + * Pause function graph tracing while performing the jprobe function. + */ + pause_graph_tracing(); + return 1; } @@ -552,6 +562,8 @@ int __kprobes longjmp_break_handler(stru * saved regs... */ memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); + /* It's OK to start function graph tracing again */ + unpause_graph_tracing(); preempt_enable_no_resched(); return 1; }
