[BUGFIX PATCH -tip] x86: Fix fixmap page order in text_poke()

[Masami Hiramatsu]

Since the fixmap pages are assigned higher address to lower, text_poke()
has to use it with inverted order (FIX_TEXT_POKE1 to FIX_TEXT_POKE0).

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
---

 arch/x86/kernel/alternative.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index f576587..4d8b40b 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -527,14 +527,18 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
 	}
 	BUG_ON(!pages[0]);
 	local_irq_save(flags);
-	set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
+	/*
+	 * Since the fixmaps are assinged from higher address to lower,
+	 * we use FIX_TEXT_POKE1 first, and FIX_TEXT_POKE0 second.
+	 */
+	set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[0]));
 	if (pages[1])
-		set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
-	vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
+		set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[1]));
+	vaddr = (char *)fix_to_virt(FIX_TEXT_POKE1);
 	memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
-	clear_fixmap(FIX_TEXT_POKE0);
+	clear_fixmap(FIX_TEXT_POKE1);
 	if (pages[1])
-		clear_fixmap(FIX_TEXT_POKE1);
+		clear_fixmap(FIX_TEXT_POKE0);
 	local_flush_tlb();
 	sync_core();
 	/* Could also do a CLFLUSH here to speed up CPU recovery; but


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx
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