diff options
authorPeter Zijlstra <peterz@infradead.org>2014-03-05 14:07:49 +0100
committerH. Peter Anvin <hpa@linux.intel.com>2014-03-06 10:58:18 -0800
commitd4078e232267ff53f3b030b9698a3c001db4dbec (patch)
parent0ac09f9f8cd1fb028a48330edba6023d347d3cea (diff)
x86, trace: Further robustify CR2 handling vs tracing
Building on commit 0ac09f9f8cd1 ("x86, trace: Fix CR2 corruption when tracing page faults") this patch addresses another few issues: - Now that read_cr2() is lifted into trace_do_page_fault(), we should pass the address to trace_page_fault_entries() to avoid it re-reading a potentially changed cr2. - Put both trace_do_page_fault() and trace_page_fault_entries() under CONFIG_TRACING. - Mark both fault entry functions {,trace_}do_page_fault() as notrace to avoid getting __mcount or other function entry trace callbacks before we've observed CR2. - Mark __do_page_fault() as noinline to guarantee the function tracer does get to see the fault. Cc: <jolsa@redhat.com> Cc: <vincent.weaver@maine.edu> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140306145300.GO9987@twins.programming.kicks-ass.net Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
1 files changed, 23 insertions, 10 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e7fa28bf3262..a10c8c792161 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1020,8 +1020,12 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
+ *
+ * This function must have noinline because both callers
+ * {,trace_}do_page_fault() have notrace on. Having this an actual function
+ * guarantees there's a function trace entry.
-static void __kprobes
+static void __kprobes noinline
__do_page_fault(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
@@ -1245,31 +1249,38 @@ good_area:
-dotraplinkage void __kprobes
+dotraplinkage void __kprobes notrace
do_page_fault(struct pt_regs *regs, unsigned long error_code)
+ unsigned long address = read_cr2(); /* Get the faulting address */
enum ctx_state prev_state;
- /* Get the faulting address: */
- unsigned long address = read_cr2();
+ /*
+ * We must have this function tagged with __kprobes, notrace and call
+ * read_cr2() before calling anything else. To avoid calling any kind
+ * of tracing machinery before we've observed the CR2 value.
+ *
+ * exception_{enter,exit}() contain all sorts of tracepoints.
+ */
prev_state = exception_enter();
__do_page_fault(regs, error_code, address);
-static void trace_page_fault_entries(struct pt_regs *regs,
+static void trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
unsigned long error_code)
if (user_mode(regs))
- trace_page_fault_user(read_cr2(), regs, error_code);
+ trace_page_fault_user(address, regs, error_code);
- trace_page_fault_kernel(read_cr2(), regs, error_code);
+ trace_page_fault_kernel(address, regs, error_code);
-dotraplinkage void __kprobes
+dotraplinkage void __kprobes notrace
trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
- enum ctx_state prev_state;
* The exception_enter and tracepoint processing could
* trigger another page faults (user space callchain
@@ -1277,9 +1288,11 @@ trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
* the faulting address now.
unsigned long address = read_cr2();
+ enum ctx_state prev_state;
prev_state = exception_enter();
- trace_page_fault_entries(regs, error_code);
+ trace_page_fault_entries(address, regs, error_code);
__do_page_fault(regs, error_code, address);
+#endif /* CONFIG_TRACING */