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authorSteven Rostedt <srostedt@redhat.com>2011-12-09 03:02:19 -0500
committerSteven Rostedt <rostedt@goodmis.org>2011-12-21 15:38:55 -0500
commit228bdaa95fb830e08b6acd1afd4d2c55093cabfa (patch)
tree11d91c3d9f5b576003a07852fcf31eb2ec53bc39 /arch/x86/include/asm/desc.h
parent3f3c8b8c4b2a34776c3470142a7c8baafcda6eb0 (diff)
x86: Keep current stack in NMI breakpoints
We want to allow NMI handlers to have breakpoints to be able to remove stop_machine from ftrace, kprobes and jump_labels. But if an NMI interrupts a current breakpoint, and then it triggers a breakpoint itself, it will switch to the breakpoint stack and corrupt the data on it for the breakpoint processing that it interrupted. Instead, have the NMI check if it interrupted breakpoint processing by checking if the stack that is currently used is a breakpoint stack. If it is, then load a special IDT that changes the IST for the debug exception to keep the same stack in kernel context. When the NMI is done, it puts it back. This way, if the NMI does trigger a breakpoint, it will keep using the same stack and not stomp on the breakpoint data for the breakpoint it interrupted. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/include/asm/desc.h')
-rw-r--r--arch/x86/include/asm/desc.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 41935fadfdfc..e95822d683f4 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -35,6 +35,8 @@ static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *in
extern struct desc_ptr idt_descr;
extern gate_desc idt_table[];
+extern struct desc_ptr nmi_idt_descr;
+extern gate_desc nmi_idt_table[];
struct gdt_page {
struct desc_struct gdt[GDT_ENTRIES];
@@ -307,6 +309,16 @@ static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit)
desc->limit = (limit >> 16) & 0xf;
}
+#ifdef CONFIG_X86_64
+static inline void set_nmi_gate(int gate, void *addr)
+{
+ gate_desc s;
+
+ pack_gate(&s, GATE_INTERRUPT, (unsigned long)addr, 0, 0, __KERNEL_CS);
+ write_idt_entry(nmi_idt_table, gate, &s);
+}
+#endif
+
static inline void _set_gate(int gate, unsigned type, void *addr,
unsigned dpl, unsigned ist, unsigned seg)
{