Steven Rostedt wrote:
On Wed, 09 Feb 2022 17:50:09 +0000
"Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx> wrote:
However, I think we will not be able to use a fixed range. I would like
to reserve instructions from function entry till the branch to
_mcount(), and it can be two or four instructions depending on whether a
function has a global entry point. For this, I am considering adding a
field in 'struct dyn_arch_ftrace', and a hook in ftrace_process_locs()
to initialize the same. I may need to override ftrace_cmp_recs().
Be careful about adding anything to dyn_arch_ftrace. powerpc already adds
the pointer to the module. Anything you add to that gets multiplied by
thousands of times (which takes up memory).
At boot up you may see something like:
ftrace: allocating 45363 entries in 178 pages
That's 45,363 dyn_arch_ftrace structures. And each module loads their own
as well. To see how many total you have after boot up:
# cat /sys/kernel/tracing/dyn_ftrace_total_info
55974 pages:295 groups: 89
That's from the same kernel. Another 10,000 entries were created by modules.
(This was for x86_64)
What you may be able to do, is to add a way to look at the already saved
kallsyms, which keeps track of the function entry and exit to know how to
map an address back to the function.
kallsyms_lookup(addr, NULL, &offset, NULL, NULL);
Should give you the offset of addr from the start of the function.
Good point. I should be able to overload the existing field for this
purpose. Is something like the below ok?
---
arch/powerpc/include/asm/ftrace.h | 13 ++++++
arch/powerpc/kernel/trace/ftrace.c | 73 ++++++++++++++++++++++++++----
kernel/trace/ftrace.c | 2 +
3 files changed, 78 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index debe8c4f706260..96d6e26cee86af 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -59,6 +59,19 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
struct dyn_arch_ftrace {
struct module *mod;
};
+
+struct dyn_ftrace;
+struct module *ftrace_mod_addr_get(struct dyn_ftrace *rec);
+void ftrace_mod_addr_set(struct dyn_ftrace *rec, struct module *mod);
+
+#ifdef CONFIG_MPROFILE_KERNEL
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+#define ftrace_init_nop ftrace_init_nop
+
+int ftrace_cmp_recs(const void *a, const void *b);
+#define ftrace_cmp_recs ftrace_cmp_recs
+#endif
+
#endif /* __ASSEMBLY__ */
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 80b6285769f27c..d9b6faa4c98a8c 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -428,21 +428,21 @@ int ftrace_make_nop(struct module *mod,
* We should either already have a pointer to the module
* or it has been passed in.
*/
- if (!rec->arch.mod) {
+ if (!ftrace_mod_addr_get(rec)) {
if (!mod) {
pr_err("No module loaded addr=%lx\n", addr);
return -EFAULT;
}
- rec->arch.mod = mod;
+ ftrace_mod_addr_set(rec, mod);
} else if (mod) {
- if (mod != rec->arch.mod) {
+ if (mod != ftrace_mod_addr_get(rec)) {
pr_err("Record mod %p not equal to passed in mod %p\n",
- rec->arch.mod, mod);
+ ftrace_mod_addr_get(rec), mod);
return -EINVAL;
}
/* nothing to do if mod == rec->arch.mod */
} else
- mod = rec->arch.mod;
+ mod = ftrace_mod_addr_get(rec);
return __ftrace_make_nop(mod, rec, addr);
#else
@@ -451,6 +451,59 @@ int ftrace_make_nop(struct module *mod,
#endif /* CONFIG_MODULES */
}
+#ifdef CONFIG_MPROFILE_KERNEL
+struct module *ftrace_mod_addr_get(struct dyn_ftrace *rec)
+{
+ return (struct module *)((unsigned long)rec->arch.mod & ~0x1);
+}
+
+void ftrace_mod_addr_set(struct dyn_ftrace *rec, struct module *mod)
+{
+ rec->arch.mod = (struct module *)(((unsigned long)rec->arch.mod & 0x1) | (unsigned long)mod);
+}
+
+bool ftrace_location_has_gep(const struct dyn_ftrace *rec)
+{
+ return !!((unsigned long)rec->arch.mod & 0x1);
+}
+
+int ftrace_cmp_recs(const void *a, const void *b)
+{
+ const struct dyn_ftrace *key = a;
+ const struct dyn_ftrace *rec = b;
+ int offset = ftrace_location_has_gep(rec) ? 12 : 4;
+
+ if (key->flags < rec->ip - offset)
+ return -1;
+ if (key->ip >= rec->ip + MCOUNT_INSN_SIZE)
+ return 1;
+ return 0;
+}
+
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+ unsigned long offset;
+
+ if (!kallsyms_lookup_size_offset(rec->ip, NULL, &offset) || (offset != 12 && offset != 4)) {
+ /* TODO: implement logic to deduce lep/gep from code */
+ } else if (offset == 12) {
+ ftrace_mod_addr_set(rec, (struct module *)1);
+ }
+
+ return ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+}
+#else
+struct module *ftrace_mod_addr_get(struct dyn_ftrace *rec)
+{
+ return rec->arch.mod;
+}
+
+void ftrace_mod_addr_set(struct dyn_ftrace *rec, struct module * mod)
+{
+ rec->arch.mod = mod;
+}
+#endif /* CONFIG_MPROFILE_KERNEL */
+
#ifdef CONFIG_MODULES
#ifdef CONFIG_PPC64
/*
@@ -494,7 +547,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
ppc_inst_t instr;
void *ip = (void *)rec->ip;
unsigned long entry, ptr, tramp;
- struct module *mod = rec->arch.mod;
+ struct module *mod = ftrace_mod_addr_get(rec);
/* read where this goes */
if (copy_inst_from_kernel_nofault(op, ip))
@@ -561,7 +614,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
int err;
ppc_inst_t op;
u32 *ip = (u32 *)rec->ip;
- struct module *mod = rec->arch.mod;
+ struct module *mod = ftrace_mod_addr_get(rec);
unsigned long tramp;
/* read where this goes */
@@ -678,7 +731,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
* Being that we are converting from nop, it had better
* already have a module defined.
*/
- if (!rec->arch.mod) {
+ if (!ftrace_mod_addr_get(rec)) {
pr_err("No module loaded\n");
return -EINVAL;
}
@@ -699,7 +752,7 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
ppc_inst_t op;
unsigned long ip = rec->ip;
unsigned long entry, ptr, tramp;
- struct module *mod = rec->arch.mod;
+ struct module *mod = ftrace_mod_addr_get(rec);
/* If we never set up ftrace trampolines, then bail */
if (!mod->arch.tramp || !mod->arch.tramp_regs) {
@@ -814,7 +867,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
/*
* Out of range jumps are called from modules.
*/
- if (!rec->arch.mod) {
+ if (!ftrace_mod_addr_get(rec)) {
pr_err("No module loaded\n");
return -EINVAL;
}
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9feb197b2daaf..68f20cf34b0c47 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1510,6 +1510,7 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
}
+#ifndef ftrace_cmp_recs
static int ftrace_cmp_recs(const void *a, const void *b)
{
const struct dyn_ftrace *key = a;
@@ -1521,6 +1522,7 @@ static int ftrace_cmp_recs(const void *a, const void *b)
return 1;
return 0;
}
+#endif
static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end)
{
Thanks,
Naveen
