On Tue, 25 Nov 2008, Andrew Morton wrote: > On Wed, 26 Nov 2008 00:16:24 -0500 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > From: Steven Rostedt <rostedt@xxxxxxxxxxx> > > > > Impact: more efficient code for ftrace graph tracer > > > > This patch uses the dynamic patching, when available, to patch > > the function graph code into the kernel. > > > > This patch will ease the way for letting both function tracing > > and function graph tracing run together. > > > > ... > > > > +static int ftrace_mod_jmp(unsigned long ip, > > + int old_offset, int new_offset) > > +{ > > + unsigned char code[MCOUNT_INSN_SIZE]; > > + > > + if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE)) > > + return -EFAULT; > > + > > + if (code[0] != 0xe9 || old_offset != *(int *)(&code[1])) > > erk. I suspect that there's a nicer way of doing this amongst our > forest of get_unaligned_foo() interfaces. Harvey will know. Hmm, I may be able to make a struct out of code. struct { unsigned char op; unsigned int offset; } code __attribute__((packed)); Would that look better? > > > + return -EINVAL; > > + > > + *(int *)(&code[1]) = new_offset; > > Might be able to use put_unaligned_foo() here. > > The problem is that these functions use sizeof(*ptr) to work out what > to do, so a cast is still needed. A get_unaligned32(ptr) would be > nice. One which takes a void* and assumes CPU ordering. Is there a correctness concern here? This is arch specific code, so I'm not worried about other archs. -- Steve > > > + if (do_ftrace_mod_code(ip, &code)) > > + return -EPERM; > > + > > + return 0; > > +} > > + > > > _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers