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authorH. Peter Anvin <hpa@linux.intel.com>2013-08-30 17:29:29 -0700
committerSteven Rostedt <rostedt@goodmis.org>2013-09-05 09:31:32 -0400
commitaf058ab04d3d11383e5159132fc78a3700be3af5 (patch)
treede93ea2d0b82f679cafb788444ed91e127abcf48 /arch
parent59338f754a55f07857342dbcd81652a4f091d72f (diff)
downloadlinux-af058ab04d3d11383e5159132fc78a3700be3af5.tar.bz2
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 <jan.kiszka@siemens.com> Tested-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/entry_32.S3
1 files changed, 3 insertions, 0 deletions
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