3.16.57-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski <luto@xxxxxxxxxx>
commit d8ba61ba58c88d5207c1ba2f7d9a2280e7d03be9 upstream.
There's nothing IST-worthy about #BP/int3. We don't allow kprobes
in the small handful of places in the kernel that run at CPL0 with
an invalid stack, and 32-bit kernels have used normal interrupt
gates for #BP forever.
Furthermore, we don't allow kprobes in places that have usergs while
in kernel mode, so "paranoid" is also unnecessary.
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[carnil: Backport to 3.16:
- Adjust finename change: arch/x86/kernel/entry_64.S
- Context changes
]
[bwh: Rebase on top of "x86/traps: Enable DEBUG_STACK after cpu_init() for
TRAP_DB/BP", and restore change in trap_init() instead of early_trap_init()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1322,7 +1322,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTO
#endif /* CONFIG_HYPERV */
idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
-idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
+idtentry int3 do_int3 has_error_code=0
idtentry stack_segment do_stack_segment has_error_code=1
#ifdef CONFIG_XEN
idtentry xen_debug do_debug has_error_code=0
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -334,7 +334,6 @@ exit:
}
NOKPROBE_SYMBOL(do_general_protection);
-/* May run on IST stack. */
dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
{
enum ctx_state prev_state;
@@ -367,15 +366,9 @@ dotraplinkage void notrace do_int3(struc
SIGTRAP) == NOTIFY_STOP)
goto exit;
- /*
- * Let others (NMI) know that the debug stack is in use
- * as we may switch to the interrupt stack.
- */
- debug_stack_usage_inc();
preempt_conditional_sti(regs);
do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
preempt_conditional_cli(regs);
- debug_stack_usage_dec();
exit:
exception_exit(prev_state);
}
@@ -862,19 +855,16 @@ void __init trap_init(void)
cpu_init();
/*
- * X86_TRAP_DB and X86_TRAP_BP have been set
- * in early_trap_init(). However, DEBUG_STACK works only after
- * cpu_init() loads TSS. See comments in early_trap_init().
+ * X86_TRAP_DB was installed in early_trap_init(). However,
+ * DEBUG_STACK works only after cpu_init() loads TSS. See comments
+ * in early_trap_init().
*/
set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
- /* int3 can be called from all */
- set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
x86_init.irqs.trap_init();
#ifdef CONFIG_X86_64
memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);
set_nmi_gate(X86_TRAP_DB, &debug);
- set_nmi_gate(X86_TRAP_BP, &int3);
#endif
}
