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Subject[PATCH kallsyms, bpf 3/3] bpf: migrate symbols for BPF programs to kallsym_tree
Date
From: Peter Zijlstra <peterz@infradead.org>

This patch migrates BPF program symbols from bpf_tree to kallsym_tree.
Since kallsym_tree_add/del already calls perf_event_ksymbol(), this patch
also removes unnecessary perf_event_bpf_emit_ksymbols().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
include/linux/bpf.h | 7 +-
include/linux/filter.h | 42 -----------
kernel/bpf/core.c | 167 +++++------------------------------------
kernel/events/core.c | 35 ---------
kernel/extable.c | 4 +-
kernel/kallsyms.c | 19 +----
6 files changed, 25 insertions(+), 249 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e734f163bd0b..403e1f88a1fa 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -13,7 +13,7 @@
#include <linux/file.h>
#include <linux/percpu.h>
#include <linux/err.h>
-#include <linux/rbtree_latch.h>
+#include <linux/kallsyms.h>
#include <linux/numa.h>
#include <linux/wait.h>

@@ -307,8 +307,9 @@ struct bpf_prog_aux {
bool offload_requested;
struct bpf_prog **func;
void *jit_data; /* JIT specific data. arch dependent */
- struct latch_tree_node ksym_tnode;
- struct list_head ksym_lnode;
+
+ struct kallsym_node ktn;
+
const struct bpf_prog_ops *ops;
struct bpf_map **used_maps;
struct bpf_prog *prog;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index d531d4250bff..61264a3f944c 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -932,23 +932,6 @@ static inline bool bpf_jit_kallsyms_enabled(void)
return false;
}

-const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char *sym);
-bool is_bpf_text_address(unsigned long addr);
-int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
- char *sym);
-
-static inline const char *
-bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char **modname, char *sym)
-{
- const char *ret = __bpf_address_lookup(addr, size, off, sym);
-
- if (ret && modname)
- *modname = NULL;
- return ret;
-}
-
void bpf_prog_kallsyms_add(struct bpf_prog *fp);
void bpf_prog_kallsyms_del(struct bpf_prog *fp);
void bpf_get_prog_name(const struct bpf_prog *prog, char *sym);
@@ -975,31 +958,6 @@ static inline bool bpf_jit_kallsyms_enabled(void)
return false;
}

-static inline const char *
-__bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char *sym)
-{
- return NULL;
-}
-
-static inline bool is_bpf_text_address(unsigned long addr)
-{
- return false;
-}
-
-static inline int bpf_get_kallsym(unsigned int symnum, unsigned long *value,
- char *type, char *sym)
-{
- return -ERANGE;
-}
-
-static inline const char *
-bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char **modname, char *sym)
-{
- return NULL;
-}
-
static inline void bpf_prog_kallsyms_add(struct bpf_prog *fp)
{
}
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 19c49313c709..e53912234a91 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -30,7 +30,6 @@
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/frame.h>
-#include <linux/rbtree_latch.h>
#include <linux/kallsyms.h>
#include <linux/rcupdate.h>
#include <linux/perf_event.h>
@@ -100,8 +99,6 @@ struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
fp->aux->prog = fp;
fp->jit_requested = ebpf_jit_enabled();

- INIT_LIST_HEAD_RCU(&fp->aux->ksym_lnode);
-
return fp;
}
EXPORT_SYMBOL_GPL(bpf_prog_alloc);
@@ -530,86 +527,38 @@ void bpf_get_prog_name(const struct bpf_prog *prog, char *sym)
*sym = 0;
}

-static __always_inline unsigned long
-bpf_get_prog_addr_start(struct latch_tree_node *n)
-{
- unsigned long symbol_start, symbol_end;
- const struct bpf_prog_aux *aux;
-
- aux = container_of(n, struct bpf_prog_aux, ksym_tnode);
- bpf_get_prog_addr_region(aux->prog, &symbol_start, &symbol_end);
-
- return symbol_start;
-}
-
-static __always_inline bool bpf_tree_less(struct latch_tree_node *a,
- struct latch_tree_node *b)
-{
- return bpf_get_prog_addr_start(a) < bpf_get_prog_addr_start(b);
-}
-
-static __always_inline int bpf_tree_comp(void *key, struct latch_tree_node *n)
-{
- unsigned long val = (unsigned long)key;
- unsigned long symbol_start, symbol_end;
- const struct bpf_prog_aux *aux;
-
- aux = container_of(n, struct bpf_prog_aux, ksym_tnode);
- bpf_get_prog_addr_region(aux->prog, &symbol_start, &symbol_end);
-
- if (val < symbol_start)
- return -1;
- if (val >= symbol_end)
- return 1;
-
- return 0;
-}
-
-static const struct latch_tree_ops bpf_tree_ops = {
- .less = bpf_tree_less,
- .comp = bpf_tree_comp,
-};
-
-static DEFINE_SPINLOCK(bpf_lock);
-static LIST_HEAD(bpf_kallsyms);
-static struct latch_tree_root bpf_tree __cacheline_aligned;
-
-static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux)
-{
- WARN_ON_ONCE(!list_empty(&aux->ksym_lnode));
- list_add_tail_rcu(&aux->ksym_lnode, &bpf_kallsyms);
- latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops);
-}
-
-static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux)
-{
- if (list_empty(&aux->ksym_lnode))
- return;
-
- latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops);
- list_del_rcu(&aux->ksym_lnode);
-}

static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp)
{
return fp->jited && !bpf_prog_was_classic(fp);
}

-static bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
+static void bpf_kn_names(struct kallsym_node *kn, char *sym, char **modname)
{
- return list_empty(&fp->aux->ksym_lnode) ||
- fp->aux->ksym_lnode.prev == LIST_POISON2;
+ struct bpf_prog_aux *aux = container_of(kn, struct bpf_prog_aux, ktn);
+
+ *modname = "eBPF-jit";
+ bpf_get_prog_name(aux->prog, sym);
}

void bpf_prog_kallsyms_add(struct bpf_prog *fp)
{
+ unsigned long sym_start, sym_end;
+
if (!bpf_prog_kallsyms_candidate(fp) ||
!capable(CAP_SYS_ADMIN))
return;

- spin_lock_bh(&bpf_lock);
- bpf_prog_ksym_node_add(fp->aux);
- spin_unlock_bh(&bpf_lock);
+ bpf_get_prog_addr_region(fp, &sym_start, &sym_end);
+
+ fp->aux->ktn.kn_addr = sym_start;
+ fp->aux->ktn.kn_len = sym_end - sym_start;
+ fp->aux->ktn.kn_names = bpf_kn_names;
+#ifdef CONFIG_PERF_EVENTS
+ fp->aux->ktn.ksym_type = PERF_RECORD_KSYMBOL_TYPE_BPF;
+#endif
+
+ kallsym_tree_add(&fp->aux->ktn);
}

void bpf_prog_kallsyms_del(struct bpf_prog *fp)
@@ -617,85 +566,7 @@ void bpf_prog_kallsyms_del(struct bpf_prog *fp)
if (!bpf_prog_kallsyms_candidate(fp))
return;

- spin_lock_bh(&bpf_lock);
- bpf_prog_ksym_node_del(fp->aux);
- spin_unlock_bh(&bpf_lock);
-}
-
-static struct bpf_prog *bpf_prog_kallsyms_find(unsigned long addr)
-{
- struct latch_tree_node *n;
-
- if (!bpf_jit_kallsyms_enabled())
- return NULL;
-
- n = latch_tree_find((void *)addr, &bpf_tree, &bpf_tree_ops);
- return n ?
- container_of(n, struct bpf_prog_aux, ksym_tnode)->prog :
- NULL;
-}
-
-const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char *sym)
-{
- unsigned long symbol_start, symbol_end;
- struct bpf_prog *prog;
- char *ret = NULL;
-
- rcu_read_lock();
- prog = bpf_prog_kallsyms_find(addr);
- if (prog) {
- bpf_get_prog_addr_region(prog, &symbol_start, &symbol_end);
- bpf_get_prog_name(prog, sym);
-
- ret = sym;
- if (size)
- *size = symbol_end - symbol_start;
- if (off)
- *off = addr - symbol_start;
- }
- rcu_read_unlock();
-
- return ret;
-}
-
-bool is_bpf_text_address(unsigned long addr)
-{
- bool ret;
-
- rcu_read_lock();
- ret = bpf_prog_kallsyms_find(addr) != NULL;
- rcu_read_unlock();
-
- return ret;
-}
-
-int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
- char *sym)
-{
- struct bpf_prog_aux *aux;
- unsigned int it = 0;
- int ret = -ERANGE;
-
- if (!bpf_jit_kallsyms_enabled())
- return ret;
-
- rcu_read_lock();
- list_for_each_entry_rcu(aux, &bpf_kallsyms, ksym_lnode) {
- if (it++ != symnum)
- continue;
-
- bpf_get_prog_name(aux->prog, sym);
-
- *value = (unsigned long)aux->prog->bpf_func;
- *type = BPF_SYM_ELF_TYPE;
-
- ret = 0;
- break;
- }
- rcu_read_unlock();
-
- return ret;
+ kallsym_tree_del(&fp->aux->ktn);
}

static atomic_long_t bpf_jit_current;
@@ -806,8 +677,6 @@ void __weak bpf_jit_free(struct bpf_prog *fp)

bpf_jit_binary_unlock_ro(hdr);
bpf_jit_binary_free(hdr);
-
- WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}

bpf_prog_unlock_free(fp);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0a8dab322111..5f6ab55f77cf 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7790,31 +7790,6 @@ static void perf_event_bpf_output(struct perf_event *event, void *data)
perf_output_end(&handle);
}

-static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog,
- enum perf_bpf_event_type type)
-{
- bool unregister = type == PERF_BPF_EVENT_PROG_UNLOAD;
- char sym[KSYM_NAME_LEN];
- int i;
-
- if (prog->aux->func_cnt == 0) {
- bpf_get_prog_name(prog, sym);
- perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF,
- (u64)(unsigned long)prog->bpf_func,
- prog->jited_len, unregister, sym);
- } else {
- for (i = 0; i < prog->aux->func_cnt; i++) {
- struct bpf_prog *subprog = prog->aux->func[i];
-
- bpf_get_prog_name(subprog, sym);
- perf_event_ksymbol(
- PERF_RECORD_KSYMBOL_TYPE_BPF,
- (u64)(unsigned long)subprog->bpf_func,
- subprog->jited_len, unregister, sym);
- }
- }
-}
-
void perf_event_bpf_event(struct bpf_prog *prog,
enum perf_bpf_event_type type,
u16 flags)
@@ -7825,16 +7800,6 @@ void perf_event_bpf_event(struct bpf_prog *prog,
type >= PERF_BPF_EVENT_MAX)
return;

- switch (type) {
- case PERF_BPF_EVENT_PROG_LOAD:
- case PERF_BPF_EVENT_PROG_UNLOAD:
- if (atomic_read(&nr_ksymbol_events))
- perf_event_bpf_emit_ksymbols(prog, type);
- break;
- default:
- break;
- }
-
if (!atomic_read(&nr_bpf_events))
return;

diff --git a/kernel/extable.c b/kernel/extable.c
index 5271e9b649b1..c7b7bd8e24f6 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -135,7 +135,7 @@ int kernel_text_address(unsigned long addr)
* coming back from idle, or cpu on or offlining.
*
* is_module_text_address() as well as the kprobe slots
- * and is_bpf_text_address() require RCU to be watching.
+ * and is_kallsym_tree_text_address() require RCU to be watching.
*/
no_rcu = !rcu_is_watching();

@@ -151,8 +151,6 @@ int kernel_text_address(unsigned long addr)
goto out;
if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
goto out;
- if (is_bpf_text_address(addr))
- goto out;
ret = 0;
out:
if (no_rcu)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 30611a5379fd..17bcc6815cf3 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -426,8 +426,7 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
if (is_ksym_addr(addr))
return !!get_symbol_pos(addr, symbolsize, offset);
return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
- !!kallsym_tree_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
- !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
+ !!kallsym_tree_address_lookup(addr, symbolsize, offset, NULL, namebuf);
}

/*
@@ -465,11 +464,6 @@ const char *kallsyms_lookup(unsigned long addr,
if (!ret)
ret = kallsym_tree_address_lookup(addr, symbolsize,
offset, modname, namebuf);
-
- if (!ret)
- ret = bpf_address_lookup(addr, symbolsize,
- offset, modname, namebuf);
-
if (!ret)
ret = ftrace_mod_address_lookup(addr, symbolsize,
offset, modname, namebuf);
@@ -674,15 +668,6 @@ static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
return 1;
}

-static int get_ksymbol_bpf(struct kallsym_iter *iter)
-{
- strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
- iter->exported = 0;
- return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
- &iter->value, &iter->type,
- iter->name) < 0 ? 0 : 1;
-}
-
/* Returns space to next name. */
static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
{
@@ -735,7 +720,7 @@ static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
get_ksymbol_ftrace_mod(iter))
return 1;

- return get_ksymbol_bpf(iter);
+ return 0;
}

/* Returns false if pos at or past end of file. */
--
2.17.1
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