Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> Split up ftrace_modify_code() into a few helpers for future use. Also
> update error messages accordingly.
>
> Signed-off-by: Naveen N Rao <nav...@kernel.org>
Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu>
> ---
> arch/powerpc/kernel/trace/ftrace.c | 51 +++++++++++++++++-------------
> 1 file changed, 29 insertions(+), 22 deletions(-)
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c
> b/arch/powerpc/kernel/trace/ftrace.c
> index 913c7aa63d3fa3..ef4e49c2c37781 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -50,32 +50,39 @@ ftrace_call_replace(unsigned long ip, unsigned long addr,
> int link)
> return op;
> }
>
> -static inline int
> -ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
> +static inline int ftrace_read_inst(unsigned long ip, ppc_inst_t *op)
> {
> - ppc_inst_t replaced;
> -
> - /*
> - * Note:
> - * We are paranoid about modifying text, as if a bug was to happen, it
> - * could cause us to read or write to someplace that could cause harm.
> - * Carefully read and modify the code with probe_kernel_*(), and make
> - * sure what we read is what we expected it to be before modifying it.
> - */
> -
> - /* read the text we want to modify */
> - if (copy_inst_from_kernel_nofault(&replaced, (void *)ip))
> + if (copy_inst_from_kernel_nofault(op, (void *)ip)) {
> + pr_err("0x%lx: fetching instruction failed\n", ip);
> return -EFAULT;
> -
> - /* Make sure it is what we expect it to be */
> - if (!ppc_inst_equal(replaced, old)) {
> - pr_err("%p: replaced (%08lx) != old (%08lx)", (void *)ip,
> - ppc_inst_as_ulong(replaced), ppc_inst_as_ulong(old));
> - return -EINVAL;
> }
>
> - /* replace the text with the new text */
> - return patch_instruction((u32 *)ip, new);
> + return 0;
> +}
> +
> +static inline int ftrace_validate_inst(unsigned long ip, ppc_inst_t inst)
> +{
> + ppc_inst_t op;
> + int ret;
> +
> + ret = ftrace_read_inst(ip, &op);
> + if (!ret && !ppc_inst_equal(op, inst)) {
> + pr_err("0x%lx: expected (%08lx) != found (%08lx)\n",
> + ip, ppc_inst_as_ulong(inst), ppc_inst_as_ulong(op));
> + ret = -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +static inline int ftrace_modify_code(unsigned long ip, ppc_inst_t old,
> ppc_inst_t new)
> +{
> + int ret = ftrace_validate_inst(ip, old);
> +
> + if (!ret)
> + ret = patch_instruction((u32 *)ip, new);
> +
> + return ret;
> }
>
> /*
