3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Andy Lutomirski luto@kernel.org
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@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Thomas Gleixner tglx@linutronix.de [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@decadent.org.uk --- --- 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 }