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Message-Id: <0ed4e63f6b3be1abdd59aa7b28a5dbdb99baeba1.1606412433.git.naveen.n.rao@linux.vnet.ibm.com>
Date: Thu, 26 Nov 2020 23:38:47 +0530
From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>,
Michael Ellerman <mpe@...erman.id.au>
Cc: <linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: [RFC PATCH 10/14] powerpc/ftrace: Drop assumptions about ftrace trampoline target
We currently assume that ftrace locations are patched to go to either
ftrace_caller or ftrace_regs_caller. Drop this assumption in preparation
for supporting ftrace direct calls.
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
arch/powerpc/kernel/trace/ftrace.c | 107 +++++++++++++++++++++++------
1 file changed, 86 insertions(+), 21 deletions(-)
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 7ddb6e4b527c39..fcb21a9756e456 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -322,14 +322,15 @@ static int add_ftrace_tramp(unsigned long tramp, unsigned long target)
*/
static int setup_mcount_compiler_tramp(unsigned long tramp)
{
+ int i;
struct ppc_inst op;
struct ppc_inst instr;
struct ppc_ftrace_stub_data *stub;
unsigned long ptr, ftrace_target = ppc_global_function_entry((void *)FTRACE_REGS_ADDR);
- /* Is this a known long jump tramp? */
- hash_for_each_possible(ppc_ftrace_stubs, stub, hentry, ftrace_target)
- if (stub->target == ftrace_target && stub->addr == tramp)
+ /* Is this a known tramp? */
+ hash_for_each(ppc_ftrace_stubs, i, stub, hentry)
+ if (stub->addr == tramp)
return 0;
/* New trampoline -- read where this goes */
@@ -608,23 +609,16 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
{
struct ppc_inst op;
void *ip = (void *)rec->ip;
- unsigned long tramp, entry, ptr;
+ unsigned long tramp, ptr;
- /* Make sure we're being asked to patch branch to a known ftrace addr */
- entry = ppc_global_function_entry((void *)ftrace_caller);
ptr = ppc_global_function_entry((void *)addr);
- if (ptr != entry) {
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
- entry = ppc_global_function_entry((void *)ftrace_regs_caller);
- if (ptr != entry) {
+ /* Make sure we branch to ftrace_regs_caller since we only setup stubs for that */
+ tramp = ppc_global_function_entry((void *)ftrace_caller);
+ if (ptr == tramp)
+ ptr = ppc_global_function_entry((void *)FTRACE_REGS_ADDR);
#endif
- pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr);
- return -EINVAL;
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
- }
-#endif
- }
/* Make sure we have a nop */
if (probe_kernel_read_inst(&op, ip)) {
@@ -637,7 +631,7 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
return -EINVAL;
}
- tramp = find_ftrace_tramp((unsigned long)ip, FTRACE_REGS_ADDR);
+ tramp = find_ftrace_tramp((unsigned long)ip, ptr);
if (!tramp) {
pr_err("No ftrace trampolines reachable from %ps\n", ip);
return -EINVAL;
@@ -783,6 +777,81 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
}
#endif
+static int
+__ftrace_modify_call_kernel(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
+{
+ struct ppc_inst op;
+ unsigned long ip = rec->ip;
+ unsigned long entry, ptr, tramp;
+
+ /* read where this goes */
+ if (probe_kernel_read_inst(&op, (void *)ip)) {
+ pr_err("Fetching opcode failed.\n");
+ return -EFAULT;
+ }
+
+ /* Make sure that this is still a 24bit jump */
+ if (!is_bl_op(op)) {
+ pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
+ return -EINVAL;
+ }
+
+ /* lets find where the pointer goes */
+ tramp = find_bl_target(ip, op);
+ entry = ppc_global_function_entry((void *)old_addr);
+
+ pr_devel("ip:%lx jumps to %lx", ip, tramp);
+
+ if (tramp != entry) {
+ /* old_addr is not within range, so we must have used a trampoline */
+ struct ppc_ftrace_stub_data *stub;
+
+ hash_for_each_possible(ppc_ftrace_stubs, stub, hentry, entry)
+ if (stub->target == entry && stub->addr == tramp)
+ break;
+
+ if (stub->target != entry || stub->addr != tramp) {
+ pr_err("we don't know about the tramp at %lx!\n", tramp);
+ return -EFAULT;
+ }
+ }
+
+ /* The new target may be within range */
+ if (test_24bit_addr(ip, addr)) {
+ /* within range */
+ if (patch_branch((struct ppc_inst *)ip, addr, BRANCH_SET_LINK)) {
+ pr_err("REL24 out of range!\n");
+ return -EINVAL;
+ }
+
+ return 0;
+ }
+
+ ptr = ppc_global_function_entry((void *)addr);
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ /* Make sure we branch to ftrace_regs_caller since we only setup stubs for that */
+ entry = ppc_global_function_entry((void *)ftrace_caller);
+ if (ptr == entry)
+ ptr = ppc_global_function_entry((void *)FTRACE_REGS_ADDR);
+#endif
+
+ tramp = find_ftrace_tramp(ip, ptr);
+
+ if (!tramp) {
+ pr_err("Couldn't find a trampoline\n");
+ return -EFAULT;
+ }
+
+ pr_devel("trampoline %lx target %lx", tramp, ptr);
+
+ if (patch_branch((struct ppc_inst *)ip, tramp, BRANCH_SET_LINK)) {
+ pr_err("REL24 out of range!\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
@@ -800,11 +869,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
new = ftrace_call_replace(ip, addr, 1);
return ftrace_modify_code(ip, old, new);
} else if (core_kernel_text(ip)) {
- /*
- * We always patch out of range locations to go to the regs
- * variant, so there is nothing to do here
- */
- return 0;
+ return __ftrace_modify_call_kernel(rec, old_addr, addr);
}
#ifdef CONFIG_MODULES
--
2.25.4
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