From f4fcbf2e093e25a7faa8a3c2a5097524114e9547 Mon Sep 17 00:00:00 2001 From: Naveen N Rao Date: Mon, 19 Jun 2023 15:17:26 +0530 Subject: [PATCH] powerpc/ftrace: Refactor ftrace_modify_code() Split up ftrace_modify_code() into a few helpers for future use. Also update error messages accordingly. Signed-off-by: Naveen N Rao Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/a8daa49712b44ff539e6c22a2ea649a540386798.1687166935.git.naveen@kernel.org --- arch/powerpc/kernel/trace/ftrace.c | 47 +++++++++++++++++------------- 1 file changed, 27 insertions(+), 20 deletions(-) diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 913c7aa63d3fa..ef4e49c2c3778 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; + if (copy_inst_from_kernel_nofault(op, (void *)ip)) { + pr_err("0x%lx: fetching instruction failed\n", ip); + return -EFAULT; + } - /* - * 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. - */ + return 0; +} - /* read the text we want to modify */ - if (copy_inst_from_kernel_nofault(&replaced, (void *)ip)) - return -EFAULT; +static inline int ftrace_validate_inst(unsigned long ip, ppc_inst_t inst) +{ + ppc_inst_t op; + int ret; - /* 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; + 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; } - /* replace the text with the new text */ - return patch_instruction((u32 *)ip, new); + 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; } /* -- 2.30.2