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authorPeter Zijlstra <peterz@infradead.org>2019-07-11 13:40:59 +0200
committerThomas Gleixner <tglx@linutronix.de>2019-07-17 23:17:38 +0200
commita0d14b8909de55139b8702fe0c7e80b69763dcfb (patch)
treea9f6b04591b9087f4a64086c27ac46c09a2f82aa /arch/x86/mm/fault.c
parentx86/entry/64: Update comments and sanity tests for create_gap (diff)
downloadlinux-dev-a0d14b8909de55139b8702fe0c7e80b69763dcfb.tar.xz
linux-dev-a0d14b8909de55139b8702fe0c7e80b69763dcfb.zip
x86/mm, tracing: Fix CR2 corruption
Despite the current efforts to read CR2 before tracing happens there still exist a number of possible holes: idtentry page_fault do_page_fault has_error_code=1 call error_entry TRACE_IRQS_OFF call trace_hardirqs_off* #PF // modifies CR2 CALL_enter_from_user_mode __context_tracking_exit() trace_user_exit(0) #PF // modifies CR2 call do_page_fault address = read_cr2(); /* whoopsie */ And similar for i386. Fix it by pulling the CR2 read into the entry code, before any of that stuff gets a chance to run and ruin things. Reported-by: He Zhe <zhe.he@windriver.com> Reported-by: Eiichi Tsukata <devel@etsukata.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Andy Lutomirski <luto@kernel.org> Cc: bp@alien8.de Cc: rostedt@goodmis.org Cc: torvalds@linux-foundation.org Cc: hpa@zytor.com Cc: dave.hansen@linux.intel.com Cc: jgross@suse.com Cc: joel@joelfernandes.org Link: https://lkml.kernel.org/r/20190711114336.116812491@infradead.org Debugged-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/mm/fault.c')
-rw-r--r--arch/x86/mm/fault.c30
1 files changed, 11 insertions, 19 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 794f364cb882..0799cc79efd3 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1507,9 +1507,8 @@ good_area:
NOKPROBE_SYMBOL(do_user_addr_fault);
/*
- * This routine handles page faults. It determines the address,
- * and the problem, and then passes it off to one of the appropriate
- * routines.
+ * Explicitly marked noinline such that the function tracer sees this as the
+ * page_fault entry point.
*/
static noinline void
__do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
@@ -1528,33 +1527,26 @@ __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
}
NOKPROBE_SYMBOL(__do_page_fault);
-static nokprobe_inline void
-trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
- unsigned long error_code)
+static __always_inline void
+trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
+ if (!trace_pagefault_enabled())
+ return;
+
if (user_mode(regs))
trace_page_fault_user(address, regs, error_code);
else
trace_page_fault_kernel(address, regs, error_code);
}
-/*
- * We must have this function blacklisted from kprobes, tagged with 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}() contains all sorts of tracepoints.
- */
-dotraplinkage void notrace
-do_page_fault(struct pt_regs *regs, unsigned long error_code)
+dotraplinkage void
+do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
- unsigned long address = read_cr2(); /* Get the faulting address */
enum ctx_state prev_state;
prev_state = exception_enter();
- if (trace_pagefault_enabled())
- trace_page_fault_entries(address, regs, error_code);
-
+ trace_page_fault_entries(regs, error_code, address);
__do_page_fault(regs, error_code, address);
exception_exit(prev_state);
}