linux-kernel - [PATCH 4.4 21/28] powerpc/64: Fix flush_(d|i)cache

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Date:   Tue, 25 Apr 2017 16:08:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oliver OHalloran <oohall@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.4 21/28] powerpc/64: Fix flush_(d|i)cache_range() called from modules

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver O'Halloran <oohall@...il.com>

commit 8f5f525d5b83f7d76a6baf9c4e94d4bf312ea7f6 upstream.

When the kernel is compiled to use 64bit ABIv2 the _GLOBAL() macro does
not include a global entry point. A function's global entry point is
used when the function is called from a different TOC context and in the
kernel this typically means a call from a module into the vmlinux (or
vice-versa).

There are a few exported asm functions declared with _GLOBAL() and
calling them from a module will likely crash the kernel since any TOC
relative load will yield garbage.

flush_icache_range() and flush_dcache_range() are both exported to
modules, and use the TOC, so must use _GLOBAL_TOC().

Fixes: 721aeaa9fdf3 ("powerpc: Build little endian ppc64 kernel with ABIv2")
Signed-off-by: Oliver O'Halloran <oohall@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kernel/misc_64.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -67,6 +67,9 @@ PPC64_CACHES:
  */

 _KPROBE(flush_icache_range)
+0:	addis	r2,r12,(.TOC. - 0b)@ha
+	addi	r2, r2,(.TOC. - 0b)@l
+	.localentry flush_icache_range, . - flush_icache_range
 BEGIN_FTR_SECTION
 	PURGE_PREFETCHED_INS
 	blr
@@ -117,7 +120,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_I
  *
  *    flush all bytes from start to stop-1 inclusive
  */
-_GLOBAL(flush_dcache_range)
+_GLOBAL_TOC(flush_dcache_range)

 /*
  * Flush the data cache to memory