[PATCH] powerpc/boot: Fix the initrd being overwritten under qemu

[Oliver O'Halloran]

When booting under OF the zImage expects the initrd address and size to be
passed to it using registers r3 and r4. SLOF (guest firmware used by QEMU)
currently doesn't do this so the zImage is not aware of the initrd
location.  This can result in initrd corruption either though the zImage
extracting the vmlinux over the initrd, or by the vmlinux overwriting the
initrd when relocating itself.

QEMU does put the linux,initrd-start and linux,initrd-end properties into
the devicetree to vmlinux to find the initrd. We can work around the SLOF
bug by also looking those properties in the zImage.

Cc: stable at vger.kernel.org
Cc: Alexey Kardashevskiy <aik at ozlabs.ru>
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
First noticed here: https://unix.stackexchange.com/questions/547023/linux-kernel-on-ppc64le-vmlinux-equivalent-in-arch-powerpc-boot
---
 arch/powerpc/boot/devtree.c | 21 +++++++++++++++++++++
 arch/powerpc/boot/main.c    |  7 +++++++
 arch/powerpc/boot/of.h      | 16 ----------------
 arch/powerpc/boot/ops.h     |  1 +
 arch/powerpc/boot/swab.h    | 17 +++++++++++++++++
 5 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/boot/devtree.c b/arch/powerpc/boot/devtree.c
index 5d91036..ac5c26b 100644
--- a/arch/powerpc/boot/devtree.c
+++ b/arch/powerpc/boot/devtree.c
@@ -13,6 +13,7 @@
 #include "string.h"
 #include "stdio.h"
 #include "ops.h"
+#include "swab.h"
 
 void dt_fixup_memory(u64 start, u64 size)
 {
@@ -318,6 +319,26 @@ int dt_xlate_reg(void *node, int res, unsigned long *addr, unsigned long *size)
 	return dt_xlate(node, res, reglen, addr, size);
 }
 
+int dt_read_addr(void *node, const char *prop, unsigned long *out_addr)
+{
+	int reglen;
+
+	*out_addr = 0;
+
+	reglen = getprop(node, prop, prop_buf, sizeof(prop_buf)) / 4;
+	if (reglen == 2) {
+		u64 v0 = be32_to_cpu(prop_buf[0]);
+		u64 v1 = be32_to_cpu(prop_buf[1]);
+		*out_addr = (v0 << 32) | v1;
+	} else if (reglen == 1) {
+		*out_addr = be32_to_cpu(prop_buf[0]);
+	} else {
+		return 0;
+	}
+
+	return 1;
+}
+
 int dt_xlate_addr(void *node, u32 *buf, int buflen, unsigned long *xlated_addr)
 {
 
diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index a9d2091..518af24 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -112,6 +112,13 @@ static struct addr_range prep_initrd(struct addr_range vmlinux, void *chosen,
 	} else if (initrd_size > 0) {
 		printf("Using loader supplied ramdisk at 0x%lx-0x%lx\n\r",
 		       initrd_addr, initrd_addr + initrd_size);
+	} else if (chosen) {
+		unsigned long initrd_end;
+
+		dt_read_addr(chosen, "linux,initrd-start", &initrd_addr);
+		dt_read_addr(chosen, "linux,initrd-end", &initrd_end);
+
+		initrd_size = initrd_end - initrd_addr;
 	}
 
 	/* If there's no initrd at all, we're done */
diff --git a/arch/powerpc/boot/of.h b/arch/powerpc/boot/of.h
index 31b2f5d..dc24770 100644
--- a/arch/powerpc/boot/of.h
+++ b/arch/powerpc/boot/of.h
@@ -26,22 +26,6 @@ typedef u16			__be16;
 typedef u32			__be32;
 typedef u64			__be64;
 
-#ifdef __LITTLE_ENDIAN__
-#define cpu_to_be16(x) swab16(x)
-#define be16_to_cpu(x) swab16(x)
-#define cpu_to_be32(x) swab32(x)
-#define be32_to_cpu(x) swab32(x)
-#define cpu_to_be64(x) swab64(x)
-#define be64_to_cpu(x) swab64(x)
-#else
-#define cpu_to_be16(x) (x)
-#define be16_to_cpu(x) (x)
-#define cpu_to_be32(x) (x)
-#define be32_to_cpu(x) (x)
-#define cpu_to_be64(x) (x)
-#define be64_to_cpu(x) (x)
-#endif
-
 #define PROM_ERROR (-1u)
 
 #endif /* _PPC_BOOT_OF_H_ */
diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
index e060676..5100dd7 100644
--- a/arch/powerpc/boot/ops.h
+++ b/arch/powerpc/boot/ops.h
@@ -95,6 +95,7 @@ void *simple_alloc_init(char *base, unsigned long heap_size,
 extern void flush_cache(void *, unsigned long);
 int dt_xlate_reg(void *node, int res, unsigned long *addr, unsigned long *size);
 int dt_xlate_addr(void *node, u32 *buf, int buflen, unsigned long *xlated_addr);
+int dt_read_addr(void *node, const char *prop, unsigned long *out);
 int dt_is_compatible(void *node, const char *compat);
 void dt_get_reg_format(void *node, u32 *naddr, u32 *nsize);
 int dt_get_virtual_reg(void *node, void **addr, int nres);
diff --git a/arch/powerpc/boot/swab.h b/arch/powerpc/boot/swab.h
index 11d2069..82db2c1 100644
--- a/arch/powerpc/boot/swab.h
+++ b/arch/powerpc/boot/swab.h
@@ -27,4 +27,21 @@ static inline u64 swab64(u64 x)
 		(u64)((x & (u64)0x00ff000000000000ULL) >> 40) |
 		(u64)((x & (u64)0xff00000000000000ULL) >> 56);
 }
+
+#ifdef __LITTLE_ENDIAN__
+#define cpu_to_be16(x) swab16(x)
+#define be16_to_cpu(x) swab16(x)
+#define cpu_to_be32(x) swab32(x)
+#define be32_to_cpu(x) swab32(x)
+#define cpu_to_be64(x) swab64(x)
+#define be64_to_cpu(x) swab64(x)
+#else
+#define cpu_to_be16(x) (x)
+#define be16_to_cpu(x) (x)
+#define cpu_to_be32(x) (x)
+#define be32_to_cpu(x) (x)
+#define cpu_to_be64(x) (x)
+#define be64_to_cpu(x) (x)
+#endif
+
 #endif /* _PPC_BOOT_SWAB_H_ */
-- 
2.9.5