powerpc/asm: Add a patch_site macro & helpers for patching instructions

Add a macro and some helper C functions for patching single asm
instructions.

The gas macro means we can do something like:

  1:	nop
  	patch_site 1b, patch__foo

Which is less visually distracting than defining a GLOBAL symbol at 1,
and also doesn't pollute the symbol table which can confuse eg. perf.

These are obviously similar to our existing feature sections, but are
not automatically patched based on CPU/MMU features, rather they are
designed to be manually patched by C code at some arbitrary point.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index e0d881ab304e..850f3b8f4da5 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -195,6 +195,22 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags)
         return patch_instruction(addr, create_branch(addr, target, flags));
 }
 
+int patch_branch_site(s32 *site, unsigned long target, int flags)
+{
+        unsigned int *addr;
+
+        addr = (unsigned int *)((unsigned long)site + *site);
+        return patch_instruction(addr, create_branch(addr, target, flags));
+}
+
+int patch_instruction_site(s32 *site, unsigned int instr)
+{
+        unsigned int *addr;
+
+        addr = (unsigned int *)((unsigned long)site + *site);
+        return patch_instruction(addr, instr);
+}
+
 bool is_offset_in_branch_range(long offset)
 {
         /*