linux-kernel - [RFC PATCH] ARM: zynq: Use memcpy_toio instead of memcpy on smp bring-up

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Date:   Tue, 30 Jul 2019 00:43:26 -0400
From:   Luis Araneda <luaraneda@...il.com>
To:     linux@...linux.org.uk, michal.simek@...inx.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Luis Araneda <luaraneda@...il.com>
Subject: [RFC PATCH] ARM: zynq: Use memcpy_toio instead of memcpy on smp bring-up

This fixes a kernel panic (read overflow) on memcpy when
FORTIFY_SOURCE is enabled.

The computed size of memcpy args are:
- p_size (dst): 4294967295 = (size_t) -1
- q_size (src): 1
- size (len): 8

Additionally, the memory is marked as __iomem, so one of
the memcpy_* functions should be used for read/write

Signed-off-by: Luis Araneda <luaraneda@...il.com>
---

For anyone trying to reproduce / debug this, it panics
before the console has any output.
I used JTAG to find the panic, but I had to comment-out
the call to "zynq_slcr_cpu_stop" as it stops the JTAG
interface and the connection is dropped, at least with OpenOCD.

I run-tested this on a Digilent Zybo Z7 board
---
 arch/arm/mach-zynq/platsmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-zynq/platsmp.c b/arch/arm/mach-zynq/platsmp.c
index a7cfe07156f4..407abade7336 100644
--- a/arch/arm/mach-zynq/platsmp.c
+++ b/arch/arm/mach-zynq/platsmp.c
@@ -57,7 +57,7 @@ int zynq_cpun_start(u32 address, int cpu)
 			* 0x4: Jump by mov instruction
 			* 0x8: Jumping address
 			*/
-			memcpy((__force void *)zero, &zynq_secondary_trampoline,
+			memcpy_toio(zero, &zynq_secondary_trampoline,
 							trampoline_size);
 			writel(address, zero + trampoline_size);
 
-- 
2.22.0