linux-kernel - [PATCH] uprobes: allow for a cache flush after ixol breakpoint creation

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Date:   Tue, 13 Dec 2016 11:40:57 +0100
From:   Marcin Nowakowski <marcin.nowakowski@...tec.com>
To:     <linux-kernel@...r.kernel.org>
CC:     <linux-mips@...ux-mips.org>, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Victor Kamensky <victor.kamensky@...aro.org>
Subject: [PATCH] uprobes: allow for a cache flush after ixol breakpoint creation

Commit 72e6ae285a1d ('ARM: 8043/1: uprobes need icache flush after xol
write' has introduced an arch-specific method to ensure all caches are
flushed appropriately after an instruction is written to an XOL page.

However, when the XOL area is created and the out-of-line breakpoint
instruction is copied, caches are not flushed at all and stale data may
be found in icache.

Replace a simple copy_to_page() with arch_uprobe_copy_ixol() to allow
the arch to ensure all caches are updated accordingly.

This change fixes uprobes on MIPS InterAptiv (tested on Creator Ci40).

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...tec.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Ingo Molnar <mingo@...hat.com>
CC: Arnaldo Carvalho de Melo <acme@...nel.org>
CC: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
CC: Victor Kamensky <victor.kamensky@...aro.org>

---
 kernel/events/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index f9ec9ad..b5916b4 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1194,7 +1194,7 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
 	/* Reserve the 1st slot for get_trampoline_vaddr() */
 	set_bit(0, area->bitmap);
 	atomic_set(&area->slot_count, 1);
-	copy_to_page(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
+	arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
 
 	if (!xol_add_vma(mm, area))
 		return area;
-- 
2.7.4