diff options
author | Peter Zijlstra <peterz@infradead.org> | 2016-12-08 16:42:15 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-12-11 13:09:20 +0100 |
commit | 11f254dbb3a2e3f0d8552d0dd37f4faa432b6b16 (patch) | |
tree | 97eb803fa0c78684a3b4ce488a70af1dfc0abed4 | |
parent | 45dbea5f55c05980cbb4c30047c71a820cd3f282 (diff) |
x86/paravirt: Fix bool return type for PVOP_CALL()
Commit:
3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
introduced a paravirt op with bool return type [*]
It turns out that the PVOP_CALL*() macros miscompile when rettype is
bool. Code that looked like:
83 ef 01 sub $0x1,%edi
ff 15 32 a0 d8 00 callq *0xd8a032(%rip) # ffffffff81e28120 <pv_lock_ops+0x20>
84 c0 test %al,%al
ended up looking like so after PVOP_CALL1() was applied:
83 ef 01 sub $0x1,%edi
48 63 ff movslq %edi,%rdi
ff 14 25 20 81 e2 81 callq *0xffffffff81e28120
48 85 c0 test %rax,%rax
Note how it tests the whole of %rax, even though a typical bool return
function only sets %al, like:
0f 95 c0 setne %al
c3 retq
This is because ____PVOP_CALL() does:
__ret = (rettype)__eax;
and while regular integer type casts truncate the result, a cast to
bool tests for any !0 value. Fix this by explicitly truncating to
sizeof(rettype) before casting.
[*] The actual bug should've been exposed in commit:
446f3dc8cc0a ("locking/core, x86/paravirt: Implement vcpu_is_preempted(cpu) for KVM and Xen guests")
but that didn't properly implement the paravirt call.
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 3cded4179481 ("x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()")
Link: http://lkml.kernel.org/r/20161208154349.346057680@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r-- | arch/x86/include/asm/paravirt_types.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 2614bd7a7839..3f2bc0f0d3e8 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -510,6 +510,18 @@ int paravirt_disable_iospace(void); #define PVOP_TEST_NULL(op) ((void)op) #endif +#define PVOP_RETMASK(rettype) \ + ({ unsigned long __mask = ~0UL; \ + switch (sizeof(rettype)) { \ + case 1: __mask = 0xffUL; break; \ + case 2: __mask = 0xffffUL; break; \ + case 4: __mask = 0xffffffffUL; break; \ + default: break; \ + } \ + __mask; \ + }) + + #define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, \ pre, post, ...) \ ({ \ @@ -537,7 +549,7 @@ int paravirt_disable_iospace(void); paravirt_clobber(clbr), \ ##__VA_ARGS__ \ : "memory", "cc" extra_clbr); \ - __ret = (rettype)__eax; \ + __ret = (rettype)(__eax & PVOP_RETMASK(rettype)); \ } \ __ret; \ }) |