Messages in this thread Patch in this message | | | Date | Fri, 3 Jul 2020 10:10:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [for-next][PATCH 04/18] x86/ftrace: Do not jump to direct code in created trampolines |
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On Thu, Jul 02, 2020 at 05:58:16PM -0400, Steven Rostedt wrote:
> + /* No need to test direct calls on created trampolines */ > + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { > + /* NOP the jnz 1f; but make sure it's a 2 byte jnz */ > + ip = trampoline + (jmp_offset - start_offset); > + if (WARN_ON(*(char *)ip != 0x75)) > + goto fail; > + ret = copy_from_kernel_nofault(ip, ideal_nops[2], 2);
I really don't get this paranoia, what's wrong with memcpy() ?
> + if (ret < 0) > + goto fail; > + }
How about something like this?
--- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -359,17 +359,11 @@ create_trampoline(struct ftrace_ops *ops npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE); /* Copy ftrace_caller onto the trampoline memory */ - ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size); - if (WARN_ON(ret < 0)) - goto fail; - - ip = trampoline + size; + memcpy(trampoline, (void *)start_offset, size); /* The trampoline ends with ret(q) */ - retq = (unsigned long)ftrace_stub; - ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); - if (WARN_ON(ret < 0)) - goto fail; + ip = trampoline + size; + memcpy(ip, text_gen_insn(RET_INSN_OPCODE, NULL, NULL), RET_INSN_SIZE); /* No need to test direct calls on created trampolines */ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { @@ -377,9 +371,7 @@ create_trampoline(struct ftrace_ops *ops ip = trampoline + (jmp_offset - start_offset); if (WARN_ON(*(char *)ip != 0x75)) goto fail; - ret = copy_from_kernel_nofault(ip, ideal_nops[2], 2); - if (ret < 0) - goto fail; + memcpy(ip, ideal_nops[2], 2); } /*
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