[PATCH v7 3/5] powerpc: Rework and improve STRICT_KERNEL_RWX patching

[Jordan Niethe]

From: "Christopher M. Riedl" <c...@bluescreens.de>

Rework code-patching with STRICT_KERNEL_RWX to prepare for a later patch
which uses a temporary mm for patching under the Book3s64 Radix MMU.
Make improvements by adding a WARN_ON when the patchsite doesn't match
after patching and return the error from __patch_instruction() properly.

Signed-off-by: Christopher M. Riedl <c...@bluescreens.de>
Signed-off-by: Jordan Niethe <jniet...@gmail.com>
---
v7: still pass addr to map_patch_area()
---
 arch/powerpc/lib/code-patching.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 29a30c3068ff..d586bf9c7581 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -75,6 +75,7 @@ static inline void stop_using_temp_mm(struct temp_mm_state 
prev_state)
 }
 
 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
+static DEFINE_PER_CPU(unsigned long, cpu_patching_addr);
 
 static int text_area_cpu_up(unsigned int cpu)
 {
@@ -87,6 +88,7 @@ static int text_area_cpu_up(unsigned int cpu)
                return -1;
        }
        this_cpu_write(text_poke_area, area);
+       this_cpu_write(cpu_patching_addr, (unsigned long)area->addr);
 
        return 0;
 }
@@ -172,11 +174,10 @@ static inline int unmap_patch_area(unsigned long addr)
 
 static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
 {
-       int err;
+       int err, rc = 0;
        u32 *patch_addr = NULL;
        unsigned long flags;
        unsigned long text_poke_addr;
-       unsigned long kaddr = (unsigned long)addr;
 
        /*
         * During early early boot patch_instruction is called
@@ -188,15 +189,13 @@ static int do_patch_instruction(u32 *addr, struct 
ppc_inst instr)
 
        local_irq_save(flags);
 
-       text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
-       if (map_patch_area(addr, text_poke_addr)) {
-               err = -1;
+       text_poke_addr = __this_cpu_read(cpu_patching_addr);
+       err = map_patch_area(addr, text_poke_addr);
+       if (err)
                goto out;
-       }
-
-       patch_addr = (u32 *)(text_poke_addr + (kaddr & ~PAGE_MASK));
 
-       __patch_instruction(addr, instr, patch_addr);
+       patch_addr = (u32 *)(text_poke_addr | offset_in_page(addr));
+       rc = __patch_instruction(addr, instr, patch_addr);
 
        err = unmap_patch_area(text_poke_addr);
        if (err)
@@ -204,8 +203,9 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst 
instr)
 
 out:
        local_irq_restore(flags);
+       WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr));
 
-       return err;
+       return rc ? rc : err;
 }
 #else /* !CONFIG_STRICT_KERNEL_RWX */
 
-- 
2.25.1