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Groups > linux.kernel > #1369958
| From | Andy Lutomirski <luto@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v5 6/9] x86/msr: Carry on after a non-"safe" MSR access fails |
| Date | 2016-04-02 16:10 +0200 |
| Message-ID | <rjupv-4TG-33@gated-at.bofh.it> (permalink) |
| References | <rjups-4TG-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
This demotes an OOPS and likely panic due to a failed non-"safe" MSR
access to a WARN_ONCE and, for RDMSR, a return value of zero.
To be clear, this type of failure should *not* happen. This patch
exists to minimize the chance of nasty undebuggable failures
happening when a CONFIG_PARAVIRT=y bug in the non-"safe" MSR helpers
gets fixed.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/msr.h | 10 ++++++++--
arch/x86/mm/extable.c | 27 +++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 93fb7c1cffda..1487054a1a70 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -92,7 +92,10 @@ static inline unsigned long long native_read_msr(unsigned int msr)
{
DECLARE_ARGS(val, low, high);
- asm volatile("rdmsr" : EAX_EDX_RET(val, low, high) : "c" (msr));
+ asm volatile("1: rdmsr\n"
+ "2:\n"
+ _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_rdmsr_unsafe)
+ : EAX_EDX_RET(val, low, high) : "c" (msr));
if (msr_tracepoint_active(__tracepoint_read_msr))
do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), 0);
return EAX_EDX_VAL(val, low, high);
@@ -119,7 +122,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
static inline void native_write_msr(unsigned int msr,
unsigned low, unsigned high)
{
- asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high) : "memory");
+ asm volatile("1: wrmsr\n"
+ "2:\n"
+ _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
+ : : "c" (msr), "a"(low), "d" (high) : "memory");
if (msr_tracepoint_active(__tracepoint_read_msr))
do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
}
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 50dfe438bd91..98b5f45d9d79 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -50,6 +50,33 @@ bool ex_handler_ext(const struct exception_table_entry *fixup,
}
EXPORT_SYMBOL(ex_handler_ext);
+bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
+ struct pt_regs *regs, int trapnr)
+{
+ WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n",
+ (unsigned int)regs->cx);
+
+ /* Pretend that the read succeeded and returned 0. */
+ regs->ip = ex_fixup_addr(fixup);
+ regs->ax = 0;
+ regs->dx = 0;
+ return true;
+}
+EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
+
+bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
+ struct pt_regs *regs, int trapnr)
+{
+ WARN_ONCE(1, "unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x)\n",
+ (unsigned int)regs->cx,
+ (unsigned int)regs->dx, (unsigned int)regs->ax);
+
+ /* Pretend that the write succeeded. */
+ regs->ip = ex_fixup_addr(fixup);
+ return true;
+}
+EXPORT_SYMBOL(ex_handler_wrmsr_unsafe);
+
bool ex_has_fault_handler(unsigned long ip)
{
const struct exception_table_entry *e;
--
2.5.5
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v5 0/9] Improve non-"safe" MSR access failure handling Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[PATCH v5 5/9] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
Re: [PATCH v5 5/9] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Borislav Petkov <bp@alien8.de> - 2016-04-03 10:50 +0200
Re: [PATCH v5 5/9] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski <luto@amacapital.net> - 2016-04-03 15:30 +0200
Re: [PATCH v5 5/9] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Borislav Petkov <bp@alien8.de> - 2016-04-03 16:10 +0200
[tip:x86/asm] x86/paravirt: Add _safe to the read_ms()r and write_msr() PV callbacks tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 8/9] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[tip:x86/asm] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 2/9] x86/head: Move the early NMI fixup into C Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[tip:x86/asm] x86/head: Move the early NMI fixup into C tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Borislav Petkov <bp@alien8.de> - 2016-04-02 20:40 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski <luto@amacapital.net> - 2016-04-02 22:20 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Borislav Petkov <bp@alien8.de> - 2016-04-02 22:50 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski <luto@amacapital.net> - 2016-04-02 23:00 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Jan Kara <jack@suse.cz> - 2016-04-04 14:00 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Peter Zijlstra <peterz@infradead.org> - 2016-04-04 14:50 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Arjan van de Ven <arjan@linux.intel.com> - 2016-04-04 17:40 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski <luto@amacapital.net> - 2016-04-04 17:40 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Peter Zijlstra <peterz@infradead.org> - 2016-04-04 18:10 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Borislav Petkov <bp@alien8.de> - 2016-04-04 21:40 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Andy Lutomirski <luto@amacapital.net> - 2016-04-04 23:40 +0200
Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception Borislav Petkov <bp@alien8.de> - 2016-04-04 23:50 +0200
[tip:x86/asm] x86/head: Move early exception panic code into early_fixup_exception() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 7/9] x86/paravirt: Add paravirt_{read,write}_msr Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
Re: [Xen-devel] [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}_msr David Vrabel <david.vrabel@citrix.com> - 2016-04-04 18:40 +0200
Re: [Xen-devel] [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}_msr Andy Lutomirski <luto@amacapital.net> - 2016-04-04 18:50 +0200
[tip:x86/asm] x86/paravirt: Add paravirt_{read,write}_msr() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 1/9] x86/head: Pass a real pt_regs and trapnr to early_fixup_exception Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[tip:x86/asm] x86/head: Pass a real pt_regs and trapnr to early_fixup_exception() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 6/9] x86/msr: Carry on after a non-"safe" MSR access fails Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[tip:x86/asm] x86/msr: Carry on after a non-"safe" MSR access fails tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
[PATCH v5 9/9] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski <luto@kernel.org> - 2016-04-02 16:10 +0200
[tip:x86/asm] x86/msr: Set the return value to zero when native_rdmsr_safe() fails tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-04-13 13:50 +0200
Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-02 16:30 +0200
Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Andy Lutomirski <luto@amacapital.net> - 2016-04-02 17:20 +0200
Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-02 17:30 +0200
Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Borislav Petkov <bp@alien8.de> - 2016-04-04 18:30 +0200
Re: [Xen-devel] [PATCH v5 0/9] Improve non-"safe" MSR access failure handling Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-04-05 17:40 +0200
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