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.
Unified · Split
| @@ -1138,7 +1138,7 @@ apicinterrupt3 HYPERV_REENLIGHTENMENT_VECTOR \ · 1137 unmodified lines | ||
| 1138 | 1138 | #endif /* CONFIG_HYPERV */ |
| 1139 | 1139 | |
| 1140 | 1140 | idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK |
| 1141 | −idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK | |
| 1141 | +idtentry int3 do_int3 has_error_code=0 | |
| 1142 | 1142 | idtentry stack_segment do_stack_segment has_error_code=1 |
| 1143 | 1143 | |
| 1144 | 1144 | #ifdef CONFIG_XEN |
| @@ -160,7 +160,6 @@ static const __initconst struct idt_data early_pf_idts[] = { · 159 unmodified lines | ||
| 160 | 160 | */ |
| 161 | 161 | static const __initconst struct idt_data dbg_idts[] = { |
| 162 | 162 | INTG(X86_TRAP_DB, debug), |
| 163 | − INTG(X86_TRAP_BP, int3), | |
| 164 | 163 | }; |
| 165 | 164 | #endif |
| 166 | 165 | |
| @@ -183,7 +182,6 @@ gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss; · 16 unmodified lines | ||
| 183 | 182 | static const __initconst struct idt_data ist_idts[] = { |
| 184 | 183 | ISTG(X86_TRAP_DB, debug, DEBUG_STACK), |
| 185 | 184 | ISTG(X86_TRAP_NMI, nmi, NMI_STACK), |
| 186 | − SISTG(X86_TRAP_BP, int3, DEBUG_STACK), | |
| 187 | 185 | ISTG(X86_TRAP_DF, double_fault, DOUBLEFAULT_STACK), |
| 188 | 186 | #ifdef CONFIG_X86_MCE |
| 189 | 187 | ISTG(X86_TRAP_MC, &machine_check, MCE_STACK), |
| @@ -577,7 +577,6 @@ do_general_protection(struct pt_regs *regs, long error_code) · 576 unmodified lines | ||
| 577 | 577 | } |
| 578 | 578 | NOKPROBE_SYMBOL(do_general_protection); |
| 579 | 579 | |
| 580 | −/* May run on IST stack. */ | |
| 581 | 580 | dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) |
| 582 | 581 | { |
| 583 | 582 | #ifdef CONFIG_DYNAMIC_FTRACE |
| @@ -592,6 +591,13 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) · 8 unmodified lines | ||
| 592 | 591 | if (poke_int3_handler(regs)) |
| 593 | 592 | return; |
| 594 | 593 | |
| 594 | + /* | |
| 595 | + * Use ist_enter despite the fact that we don't use an IST stack. | |
| 596 | + * We can be called from a kprobe in non-CONTEXT_KERNEL kernel | |
| 597 | + * mode or even during context tracking state changes. | |
| 598 | + * | |
| 599 | + * This means that we can't schedule. That's okay. | |
| 600 | + */ | |
| 595 | 601 | ist_enter(regs); |
| 596 | 602 | RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); |
| 597 | 603 | #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP |
| @@ -609,15 +615,10 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) · 11 unmodified lines | ||
| 609 | 615 | SIGTRAP) == NOTIFY_STOP) |
| 610 | 616 | goto exit; |
| 611 | 617 | |
| 612 | − /* | |
| 613 | − * Let others (NMI) know that the debug stack is in use | |
| 614 | − * as we may switch to the interrupt stack. | |
| 615 | − */ | |
| 616 | − debug_stack_usage_inc(); | |
| 617 | 618 | cond_local_irq_enable(regs); |
| 618 | 619 | do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL); |
| 619 | 620 | cond_local_irq_disable(regs); |
| 620 | − debug_stack_usage_dec(); | |
| 621 | + | |
| 621 | 622 | exit: |
| 622 | 623 | ist_exit(regs); |
| 623 | 624 | } |