From: H. Peter Anvin Date: Sat, 31 Aug 2013 00:29:29 +0000 (-0700) Subject: x86-32, ftrace: Fix static ftrace when early microcode is enabled X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=af058ab04d3d11383e5159132fc78a3700be3af5;p=linux-beck.git x86-32, ftrace: Fix static ftrace when early microcode is enabled Early microcode loading runs C code before paging is enabled on 32 bits. Since ftrace puts a hook into every function, that hook needs to be safe to execute in the pre-paging environment. This is currently true for dynamic ftrace but not for static ftrace. Static ftrace is obsolescent and assumed to not be performance-critical, so we can simply test that the stack pointer falls within the valid range of kernel addresses. Reported-by: Jan Kiszka Tested-by: Jan Kiszka Signed-off-by: H. Peter Anvin Signed-off-by: Steven Rostedt --- diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 2cfbc3a3a2dd..f0dcb0ceb6a2 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -1176,6 +1176,9 @@ ftrace_restore_flags: #else /* ! CONFIG_DYNAMIC_FTRACE */ ENTRY(mcount) + cmpl $__PAGE_OFFSET, %esp + jb ftrace_stub /* Paging not enabled yet? */ + cmpl $0, function_trace_stop jne ftrace_stub