linux-kernel - [PATCH 4/6] pgo: modules Enable __llvm_profile_instrument

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Message-Id: <20210528201006.459292-1-jarmo.tiitto@gmail.com>
Date:   Fri, 28 May 2021 23:10:06 +0300
From:   Jarmo Tiitto <jarmo.tiitto@...il.com>
To:     samitolvanen@...gle.com
Cc:     wcw@...gle.com, nathan@...nel.org, ndesaulniers@...gle.com,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Jarmo Tiitto <jarmo.tiitto@...il.com>
Subject: [PATCH 4/6] pgo: modules Enable __llvm_profile_instrument_target() for modules

Enable allocate_node() for modules.

Before this patch __llvm_profile_instrument_target() profiled all
code which was instrumented, including modules.
Any module profiling was however effectively disabled by allocate_node()
if llvm_prf_data instance didn't point into core section.

Handle profiling data that orginates from modules by iterating
prf_mod_list and checking in what module the llvm_prf_data instance
points into.
If matching module is found the node is allocated from that module.
Each module has then its own current_node index.
The list iteration is protected by rcu here to avoid extra mutex.

Signed-off-by: Jarmo Tiitto <jarmo.tiitto@...il.com>
---
 kernel/pgo/instrument.c | 65 +++++++++++++++++++++++++++++++++--------
 1 file changed, 53 insertions(+), 12 deletions(-)

diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c
index 98cfa11a7b76..a95c86d668b5 100644
--- a/kernel/pgo/instrument.c
+++ b/kernel/pgo/instrument.c
@@ -31,7 +31,7 @@
  * ensures that we don't try to serialize data that's only partially updated.
  */
 static DEFINE_SPINLOCK(pgo_lock);
-static int current_node;
+static int current_node = 0;
 
 unsigned long prf_lock(void)
 {
@@ -55,17 +55,58 @@ void prf_unlock(unsigned long flags)
 static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p,
 						 u32 index, u64 value)
 {
-	if (&__llvm_prf_vnds_start[current_node + 1] >= __llvm_prf_vnds_end)
-		return NULL; /* Out of nodes */
-
-	current_node++;
-
-	/* Make sure the node is entirely within the section */
-	if (&__llvm_prf_vnds_start[current_node] >= __llvm_prf_vnds_end ||
-	    &__llvm_prf_vnds_start[current_node + 1] > __llvm_prf_vnds_end)
-		return NULL;
-
-	return &__llvm_prf_vnds_start[current_node];
+    struct prf_mod_private_data *pmod;
+    struct llvm_prf_data *start = __llvm_prf_data_start;
+    struct llvm_prf_data *end = __llvm_prf_data_end;
+    struct module * mod;
+    struct llvm_prf_value_node * vnds = __llvm_prf_vnds_start;
+    struct llvm_prf_value_node * vnds_end = __llvm_prf_vnds_end;
+
+    if(start <= p && p < end) {
+        /* vmlinux core node */
+        if (&vnds[current_node + 1] >= vnds_end)
+            return NULL; /* Out of nodes */
+
+        current_node++;
+
+        /* Make sure the node is entirely within the section
+         */
+        if (&vnds[current_node] >= vnds_end ||
+            &vnds[current_node + 1] > vnds_end)
+            return NULL;
+
+        return &vnds[current_node];
+
+    } else {
+        /* maybe an module node
+         * find in what module section p points into and
+         * then allocate from that module
+         */
+        rcu_read_lock();
+        list_for_each_entry_rcu(pmod,&prf_mod_list,link) {
+            mod = READ_ONCE(pmod->mod);
+            if(mod) {
+                /* get section bounds */
+                start = mod->prf_data;
+                end = mod->prf_data + mod->prf_data_size;
+                if(start <= p && p < end)
+                {
+                    vnds = mod->prf_vnds;
+                    vnds_end = mod->prf_vnds + mod->prf_vnds_size;
+                    if (&vnds[pmod->current_node + 1] < vnds_end) {
+                        pmod->current_node++;
+
+                        vnds = &vnds[pmod->current_node];
+                        rcu_read_unlock();
+                        return vnds;
+                        break;
+                    }
+                }
+            }
+        }
+        rcu_read_unlock();
+        return NULL; /* Out of nodes */
+    }
 }
 
 /*
-- 
2.31.1