From: "tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>, x86 <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: [tip: x86/entry] x86/entry: Fix #UD vs WARN more
Date: Thu, 25 Jun 2020 11:53:32 -0000 [thread overview]
Message-ID: <159308601215.16989.11684885436197238827.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200622114713.GE577403@hirez.programming.kicks-ass.net>
The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 145a773aef83181d47ebab21bb33c89233aadb1e
Gitweb: https://git.kernel.org/tip/145a773aef83181d47ebab21bb33c89233aadb1e
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 16 Jun 2020 13:28:36 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 25 Jun 2020 13:45:40 +02:00
x86/entry: Fix #UD vs WARN more
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: 15a416e8aaa7 ("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
---
arch/x86/kernel/traps.c | 72 +++++++++++++++++++++-------------------
1 file changed, 38 insertions(+), 34 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index a7d1570..1d9ea21 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -84,17 +84,16 @@ static inline void cond_local_irq_disable(struct pt_regs *regs)
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)
return 0;
- if (probe_kernel_address((unsigned short *)addr, ud))
- return 0;
-
- return ud == INSN_UD0 || ud == INSN_UD2;
+ /*
+ * We got #UD, if the text isn't readable we'd have gotten
+ * a different exception.
+ */
+ return *(unsigned short *)addr == INSN_UD2;
}
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));
}
-DEFINE_IDTENTRY_RAW(exc_invalid_op)
+static noinstr bool handle_bug(struct pt_regs *regs)
{
- bool rcu_exit;
+ bool handled = false;
+
+ if (!is_valid_bugaddr(regs->ip))
+ return handled;
/*
- * 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.
+ * All lies, just get the WARN/BUG out.
*/
- if (!user_mode(regs) && is_valid_bugaddr(regs->ip)) {
- enum bug_trap_type type;
+ 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();
- 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();
+ return handled;
+}
- if (type == BUG_TRAP_TYPE_WARN) {
- /* Skip the ud2. */
- regs->ip += LEN_UD2;
- return;
- }
+DEFINE_IDTENTRY_RAW(exc_invalid_op)
+{
+ bool rcu_exit;
- /*
- * 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.
- */
- }
+ /*
+ * We use UD2 as a short encoding for 'CALL __WARN', as such
+ * handle it before exception entry to avoid recursive WARN
+ * in case exception entry is the one triggering WARNs.
+ */
+ if (!user_mode(regs) && handle_bug(regs))
+ return;
rcu_exit = idtentry_enter_cond_rcu(regs);
instrumentation_begin();
next prev parent reply other threads:[~2020-06-25 11:54 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 14:44 [PATCH 0/7] x86/entry: noinstr fixes Peter Zijlstra
2020-06-18 14:44 ` [PATCH 1/7] x86/entry: Fix #UD vs WARN more Peter Zijlstra
2020-06-18 14:57 ` Andy Lutomirski
2020-06-18 15:50 ` Peter Zijlstra
2020-06-18 18:36 ` Andy Lutomirski
2020-06-18 19:02 ` Peter Zijlstra
2020-06-18 19:29 ` Andy Lutomirski
2020-06-18 21:18 ` Peter Zijlstra
2020-06-22 11:47 ` Peter Zijlstra
2020-06-24 22:37 ` Andy Lutomirski
2020-06-25 11:53 ` tip-bot2 for Peter Zijlstra [this message]
2020-06-18 14:44 ` [PATCH 2/7] objtool: Dont consider vmlinux a C-file Peter Zijlstra
2020-06-25 11:53 ` [tip: x86/entry] objtool: Don't " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 3/7] x86/entry: Fixup bad_iret vs noinstr Peter Zijlstra
2020-06-18 15:13 ` Marco Elver
2020-06-25 11:53 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 4/7] x86/entry: Increase entry_stack size to a full page Peter Zijlstra
2020-06-18 15:06 ` Marco Elver
2020-06-19 3:10 ` Lai Jiangshan
2020-06-25 11:53 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 5/7] objtool: Clean up elf_write() condition Peter Zijlstra
2020-06-18 14:44 ` [PATCH 6/7] objtool: Provide elf_write_{insn,reloc}() Peter Zijlstra
2020-06-18 14:44 ` [PATCH 7/7] objtool: Fix noinstr vs KCOV Peter Zijlstra
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