Re: [PATCH 1/5] powerpc/asm: Add a patch_site macro & helpers for patching instructions

Christophe LEROY [off-list ref] writes:

Le 08/08/2018 =C3=A0 18:30, Christophe LEROY a =C3=A9crit=C2=A0:

quoted

Le 23/07/2018 =C3=A0 17:07, Michael Ellerman a =C3=A9crit=C2=A0:

...

quoted

quoted

diff --git a/arch/powerpc/include/asm/code-patching.h=20

b/arch/powerpc/include/asm/code-patching.h
index 812535f40124..b2051234ada8 100644

--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h

@@ -32,6 +32,8 @@ unsigned int create_cond_branch(const unsigned int=20

*addr,
=C2=A0 int patch_branch(unsigned int *addr, unsigned long target, int f=

lags);

quoted

quoted

=C2=A0 int patch_instruction(unsigned int *addr, unsigned int instr);
=C2=A0 int raw_patch_instruction(unsigned int *addr, unsigned int instr=

);

quoted

quoted

+int patch_instruction_site(s32 *addr, unsigned int instr);
+int patch_branch_site(s32 *site, unsigned long target, int flags);

=20
Why use s32* instead of unsigned int* as usual for pointer to code ?

Forget my stupid question, I didn't see it was a relative address and=20
not an absolute one.

No worries.=20

It is a bit non-obvious at first glance, it looks like the s32 * points
to the instruction. But it points to the s32 that holds the relative
offset from itself, of the instruction.

We could add a typedef to try and make that more obvious, but I
generally don't like typedefs that hide pointerness.

cheers