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x86/entry: Fix #UD vs WARN more

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vmlinux.o: warning: objtool: exc_invalid_op()+0x47: call to probe_kernel_read() leaves .noinstr.text section

Since we use UD2 as a short-cut for 'CALL __WARN', treat it as such.
Have the bare exception handler do the report_bug() thing.

Fixes: 15a416e8aa ("x86/entry: Treat BUG/WARN as NMI-like entries")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200622114713.GE577403@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2020-06-16 13:28:36 +02:00
parent c7aadc0932
commit 145a773aef
1 changed files with 39 additions and 35 deletions
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74
arch/x86/kernel/traps.c
View file

@ -84,17 +84,16 @@ static inline void cond_local_irq_disable(struct pt_regs *regs)
local_irq_disable(); local_irq_disable();
} }
int is_valid_bugaddr(unsigned long addr) __always_inline int is_valid_bugaddr(unsigned long addr)
{ {
unsigned short ud;
if (addr < TASK_SIZE_MAX) if (addr < TASK_SIZE_MAX)
return 0; return 0;
if (probe_kernel_address((unsigned short *)addr, ud)) /*
return 0; * We got #UD, if the text isn't readable we'd have gotten
* a different exception.
return ud == INSN_UD0 || ud == INSN_UD2; */
return *(unsigned short *)addr == INSN_UD2;
} }
static nokprobe_inline int static nokprobe_inline int
@ -216,40 +215,45 @@ static inline void handle_invalid_op(struct pt_regs *regs)
ILL_ILLOPN, error_get_trap_addr(regs)); ILL_ILLOPN, error_get_trap_addr(regs));
} }
static noinstr bool handle_bug(struct pt_regs *regs)
{
bool handled = false;
if (!is_valid_bugaddr(regs->ip))
return handled;
/*
* All lies, just get the WARN/BUG out.
*/
instrumentation_begin();
/*
* Since we're emulating a CALL with exceptions, restore the interrupt
* state to what it was at the exception site.
*/
if (regs->flags & X86_EFLAGS_IF)
raw_local_irq_enable();
if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN) {
regs->ip += LEN_UD2;
handled = true;
}
if (regs->flags & X86_EFLAGS_IF)
raw_local_irq_disable();
instrumentation_end();
return handled;
}
DEFINE_IDTENTRY_RAW(exc_invalid_op) DEFINE_IDTENTRY_RAW(exc_invalid_op)
{ {
bool rcu_exit; bool rcu_exit;
/* /*
* Handle BUG/WARN like NMIs instead of like normal idtentries: * We use UD2 as a short encoding for 'CALL __WARN', as such
* if we bugged/warned in a bad RCU context, for example, the last * handle it before exception entry to avoid recursive WARN
* thing we want is to BUG/WARN again in the idtentry code, ad * in case exception entry is the one triggering WARNs.
* infinitum.
*/ */
if (!user_mode(regs) && is_valid_bugaddr(regs->ip)) { if (!user_mode(regs) && handle_bug(regs))
enum bug_trap_type type; return;
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); rcu_exit = idtentry_enter_cond_rcu(regs);
instrumentation_begin(); instrumentation_begin();