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-rw-r--r--arch/x86/include/asm/nospec-branch.h24
-rw-r--r--arch/x86/mm/extable.c16
-rw-r--r--include/linux/once_lite.h20
3 files changed, 43 insertions, 17 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 38a3e86e665e..cba942006ffe 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -94,25 +94,37 @@
.endm
/*
+ * Equivalent to -mindirect-branch-cs-prefix; emit the 5 byte jmp/call
+ * to the retpoline thunk with a CS prefix when the register requires
+ * a RAX prefix byte to encode. Also see apply_retpolines().
+ */
+.macro __CS_PREFIX reg:req
+ .irp rs,r8,r9,r10,r11,r12,r13,r14,r15
+ .ifc \reg,\rs
+ .byte 0x2e
+ .endif
+ .endr
+.endm
+
+/*
* JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple
* indirect jmp/call which may be susceptible to the Spectre variant 2
* attack.
*/
.macro JMP_NOSPEC reg:req
#ifdef CONFIG_RETPOLINE
- ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
- __stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
- __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE
+ __CS_PREFIX \reg
+ jmp __x86_indirect_thunk_\reg
#else
jmp *%\reg
+ int3
#endif
.endm
.macro CALL_NOSPEC reg:req
#ifdef CONFIG_RETPOLINE
- ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *%\reg), \
- __stringify(call __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
- __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_LFENCE
+ __CS_PREFIX \reg
+ call __x86_indirect_thunk_\reg
#else
call *%\reg
#endif
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index dba2197c05c3..331310c29349 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -94,16 +94,18 @@ static bool ex_handler_copy(const struct exception_table_entry *fixup,
static bool ex_handler_msr(const struct exception_table_entry *fixup,
struct pt_regs *regs, bool wrmsr, bool safe, int reg)
{
- if (!safe && wrmsr &&
- pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
- (unsigned int)regs->cx, (unsigned int)regs->dx,
- (unsigned int)regs->ax, regs->ip, (void *)regs->ip))
+ if (__ONCE_LITE_IF(!safe && wrmsr)) {
+ pr_warn("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
+ (unsigned int)regs->cx, (unsigned int)regs->dx,
+ (unsigned int)regs->ax, regs->ip, (void *)regs->ip);
show_stack_regs(regs);
+ }
- if (!safe && !wrmsr &&
- pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
- (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
+ if (__ONCE_LITE_IF(!safe && !wrmsr)) {
+ pr_warn("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
+ (unsigned int)regs->cx, regs->ip, (void *)regs->ip);
show_stack_regs(regs);
+ }
if (!wrmsr) {
/* Pretend that the read succeeded and returned 0. */
diff --git a/include/linux/once_lite.h b/include/linux/once_lite.h
index 861e606b820f..b7bce4983638 100644
--- a/include/linux/once_lite.h
+++ b/include/linux/once_lite.h
@@ -9,15 +9,27 @@
*/
#define DO_ONCE_LITE(func, ...) \
DO_ONCE_LITE_IF(true, func, ##__VA_ARGS__)
-#define DO_ONCE_LITE_IF(condition, func, ...) \
+
+#define __ONCE_LITE_IF(condition) \
({ \
static bool __section(".data.once") __already_done; \
- bool __ret_do_once = !!(condition); \
+ bool __ret_cond = !!(condition); \
+ bool __ret_once = false; \
\
- if (unlikely(__ret_do_once && !__already_done)) { \
+ if (unlikely(__ret_cond && !__already_done)) { \
__already_done = true; \
- func(__VA_ARGS__); \
+ __ret_once = true; \
} \
+ unlikely(__ret_once); \
+ })
+
+#define DO_ONCE_LITE_IF(condition, func, ...) \
+ ({ \
+ bool __ret_do_once = !!(condition); \
+ \
+ if (__ONCE_LITE_IF(__ret_do_once)) \
+ func(__VA_ARGS__); \
+ \
unlikely(__ret_do_once); \
})