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powerpc/ftrace: Refactor ftrace_modify_code()

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Split up ftrace_modify_code() into a few helpers for future use. Also
update error messages accordingly.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/a8daa49712b44ff539e6c22a2ea649a540386798.1687166935.git.naveen@kernel.org
This commit is contained in:
Naveen N Rao 2023-06-19 15:17:26 +05:30 committed by Michael Ellerman
parent bad90aa52d
commit f4fcbf2e09
1 changed files with 29 additions and 22 deletions
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51
arch/powerpc/kernel/trace/ftrace.c
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@ -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;
}
/*