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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>
This commit is contained in:
H. Peter Anvin 2013-08-30 17:29:29 -07:00 committed by Steven Rostedt
parent 59338f754a
commit af058ab04d
1 changed files with 3 additions and 0 deletions
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3
arch/x86/kernel/entry_32.S
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@ -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