Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Thomas Gleixner:
"Two bugfixes from Andy addressing at least some of the subtle NMI
related wreckage which has been reported by Sasha Levin"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code
x86/paravirt: Replace the paravirt nop with a bona fide empty function
+27
-5
+15
-1
arch/x86/entry/entry_64.S
+15
-1
arch/x86/entry/entry_64.S
···
1128
1128
1129
1129
/* Runs on exception stack */
1130
1130
ENTRY(nmi)
1131
+
/*
1132
+
* Fix up the exception frame if we're on Xen.
1133
+
* PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most
1134
+
* one value to the stack on native, so it may clobber the rdx
1135
+
* scratch slot, but it won't clobber any of the important
1136
+
* slots past it.
1137
+
*
1138
+
* Xen is a different story, because the Xen frame itself overlaps
1139
+
* the "NMI executing" variable.
1140
+
*/
1131
1141
PARAVIRT_ADJUST_EXCEPTION_FRAME
1142
+
1132
1143
/*
1133
1144
* We allow breakpoints in NMIs. If a breakpoint occurs, then
1134
1145
* the iretq it performs will take us out of NMI context.
···
1190
1179
* we don't want to enable interrupts, because then we'll end
1191
1180
* up in an awkward situation in which IRQs are on but NMIs
1192
1181
* are off.
1182
+
*
1183
+
* We also must not push anything to the stack before switching
1184
+
* stacks lest we corrupt the "NMI executing" variable.
1193
1185
*/
1194
1186
1195
-
SWAPGS
1187
+
SWAPGS_UNSAFE_STACK
1196
1188
cld
1197
1189
movq %rsp, %rdx
1198
1190
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+12
-4
arch/x86/kernel/paravirt.c
+12
-4
arch/x86/kernel/paravirt.c
···
41
41
#include <asm/timer.h>
42
42
#include <asm/special_insns.h>
43
43
44
-
/* nop stub */
45
-
void _paravirt_nop(void)
46
-
{
47
-
}
44
+
/*
45
+
* nop stub, which must not clobber anything *including the stack* to
46
+
* avoid confusing the entry prologues.
47
+
*/
48
+
extern void _paravirt_nop(void);
49
+
asm (".pushsection .entry.text, \"ax\"\n"
50
+
".global _paravirt_nop\n"
51
+
"_paravirt_nop:\n\t"
52
+
"ret\n\t"
53
+
".size _paravirt_nop, . - _paravirt_nop\n\t"
54
+
".type _paravirt_nop, @function\n\t"
55
+
".popsection");
48
56
49
57
/* identity function, which can be inlined */
50
58
u32 _paravirt_ident_32(u32 x)