[PATCH v2] powerpc: fix boot on BOOK3S_32 with CONFIG_STRICT_KERNEL_RWX

From: Christophe Leroy
Date: Tue Nov 21 2017 - 09:27:01 EST

On powerpc32, patch_instruction() is called by apply_feature_fixups()
which is called from early_init()

There is the following note in front of early_init():
* Note that the kernel may be running at an address which is different
* from the address that it was linked at, so we must use RELOC/PTRRELOC
* to access static data (including strings). -- paulus

Therefore, slab_is_available() cannot be called yet, and
text_poke_area must be addressed with PTRRELOC()

Fixes: 37bc3e5fd764f ("powerpc/lib/code-patching: Use alternate map
for patch_instruction()")
Reported-by: Meelis Roos <mroos@xxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
v2: Added missing asm/setup.h

arch/powerpc/lib/code-patching.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index c9de03e0c1f1..d469224c4ada 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -21,6 +21,7 @@
#include <asm/tlbflush.h>
#include <asm/page.h>
#include <asm/code-patching.h>
+#include <asm/setup.h>

static int __patch_instruction(unsigned int *addr, unsigned int instr)
@@ -146,11 +147,8 @@ int patch_instruction(unsigned int *addr, unsigned int instr)
* During early early boot patch_instruction is called
* when text_poke_area is not ready, but we still need
* to allow patching. We just do the plain old patching
- * We use slab_is_available and per cpu read * via this_cpu_read
- * of text_poke_area. Per-CPU areas might not be up early
- * this can create problems with just using this_cpu_read()
- if (!slab_is_available() || !this_cpu_read(text_poke_area))
+ if (!this_cpu_read(*PTRRELOC(&text_poke_area)))
return __patch_instruction(addr, instr);