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authorStephen Boyd <sboyd@codeaurora.org>2015-10-02 11:15:13 -0700
committerStephen Boyd <sboyd@codeaurora.org>2015-10-02 11:22:23 -0700
commit9f30a04d768f64280dc0c40b730746e82f298d88 (patch)
treee112853eb73627ed7b9a2ef8e4feab6685a0200e /arch/mips/include/asm/stackframe.h
parent9e294bf88a583825a413df408b9fe9e658fb93ac (diff)
parent7aba4f5201d1b7b3ddb0b03883d9edf69851ddad (diff)
Merge branch 'for-4.3-rc/ti-clk-fixes' of https://github.com/t-kristo/linux-pm into clk-fixes
Pull fixes from Tero Kristo: "A few TI clock driver fixes to pull against 4.3-rc" * 'for-4.3-rc/ti-clk-fixes' of https://github.com/t-kristo/linux-pm: (3 commits) clk: ti: dflt: fix enable_reg validity check clk: ti: fix dual-registration of uart4_ick clk: ti: clk-7xx: Remove hardwired ABE clock configuration
Diffstat (limited to 'arch/mips/include/asm/stackframe.h')
-rw-r--r--arch/mips/include/asm/stackframe.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index 28d6d9364bd1f..a71da576883c8 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -152,6 +152,31 @@
.set noreorder
bltz k0, 8f
move k1, sp
+#ifdef CONFIG_EVA
+ /*
+ * Flush interAptiv's Return Prediction Stack (RPS) by writing
+ * EntryHi. Toggling Config7.RPS is slower and less portable.
+ *
+ * The RPS isn't automatically flushed when exceptions are
+ * taken, which can result in kernel mode speculative accesses
+ * to user addresses if the RPS mispredicts. That's harmless
+ * when user and kernel share the same address space, but with
+ * EVA the same user segments may be unmapped to kernel mode,
+ * even containing sensitive MMIO regions or invalid memory.
+ *
+ * This can happen when the kernel sets the return address to
+ * ret_from_* and jr's to the exception handler, which looks
+ * more like a tail call than a function call. If nested calls
+ * don't evict the last user address in the RPS, it will
+ * mispredict the return and fetch from a user controlled
+ * address into the icache.
+ *
+ * More recent EVA-capable cores with MAAR to restrict
+ * speculative accesses aren't affected.
+ */
+ MFC0 k0, CP0_ENTRYHI
+ MTC0 k0, CP0_ENTRYHI
+#endif
.set reorder
/* Called from user mode, new stack. */
get_saved_sp