diff options
| author | Andy Lutomirski <luto@kernel.org> | 2020-06-11 20:26:38 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-06-12 12:12:57 +0200 |
| commit | 15a416e8aaa758b5534f64a3972dae05275bc225 (patch) | |
| tree | e4ae9ce3068dbd6df81a2a445be81e015a387aa5 /arch/x86/kernel/traps.c | |
| parent | f0178fc01fe46bab6a95415f5647d1a74efcad1b (diff) | |
x86/entry: Treat BUG/WARN as NMI-like entries
BUG/WARN are cleverly optimized using UD2 to handle the BUG/WARN out of
line in an exception fixup.
But if BUG or WARN is issued in a funny RCU context, then the
idtentry_enter...() path might helpfully WARN that the RCU context is
invalid, which results in infinite recursion.
Split the BUG/WARN handling into an nmi_enter()/nmi_exit() path in
exc_invalid_op() to increase the chance to survive the experience.
[ tglx: Make the declaration match the implementation ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/f8fe40e0088749734b4435b554f73eee53dcf7a8.1591932307.git.luto@kernel.org
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 64 |
1 files changed, 38 insertions, 26 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 7febae381b91..af75109485c2 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -97,24 +97,6 @@ int is_valid_bugaddr(unsigned long addr) return ud == INSN_UD0 || ud == INSN_UD2; } -int fixup_bug(struct pt_regs *regs, int trapnr) -{ - if (trapnr != X86_TRAP_UD) - return 0; - - switch (report_bug(regs->ip, regs)) { - case BUG_TRAP_TYPE_NONE: - case BUG_TRAP_TYPE_BUG: - break; - - case BUG_TRAP_TYPE_WARN: - regs->ip += LEN_UD2; - return 1; - } - - return 0; -} - static nokprobe_inline int do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str, struct pt_regs *regs, long error_code) @@ -190,13 +172,6 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str, { RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); - /* - * WARN*()s end up here; fix them up before we call the - * notifier chain. - */ - if (!user_mode(regs) && fixup_bug(regs, trapnr)) - return; - if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != NOTIFY_STOP) { cond_local_irq_enable(regs); @@ -241,9 +216,46 @@ static inline void handle_invalid_op(struct pt_regs *regs) ILL_ILLOPN, error_get_trap_addr(regs)); } -DEFINE_IDTENTRY(exc_invalid_op) +DEFINE_IDTENTRY_RAW(exc_invalid_op) { + bool rcu_exit; + + /* + * Handle BUG/WARN like NMIs instead of like normal idtentries: + * if we bugged/warned in a bad RCU context, for example, the last + * thing we want is to BUG/WARN again in the idtentry code, ad + * infinitum. + */ + if (!user_mode(regs) && is_valid_bugaddr(regs->ip)) { + enum bug_trap_type type; + + nmi_enter(); + instrumentation_begin(); + trace_hardirqs_off_finish(); + type = report_bug(regs->ip, regs); + if (regs->flags & X86_EFLAGS_IF) + trace_hardirqs_on_prepare(); + instrumentation_end(); + nmi_exit(); + + if (type == BUG_TRAP_TYPE_WARN) { + /* Skip the ud2. */ + regs->ip += LEN_UD2; + return; + } + + /* + * Else, if this was a BUG and report_bug returns or if this + * was just a normal #UD, we want to continue onward and + * crash. + */ + } + + rcu_exit = idtentry_enter_cond_rcu(regs); + instrumentation_begin(); handle_invalid_op(regs); + instrumentation_end(); + idtentry_exit_cond_rcu(regs, rcu_exit); } DEFINE_IDTENTRY(exc_coproc_segment_overrun) |