2022-06-06 21:07:42

by Jiri Olsa

[permalink] [raw]
Subject: [PATCHv2 bpf 2/3] ftrace: Keep address offset in ftrace_lookup_symbols

We want to store the resolved address on the same index as
the symbol string, because that's the user (bpf kprobe link)
code assumption.

Also making sure we don't store duplicates that might be
present in kallsyms.

Acked-by: Song Liu <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>
Fixes: bed0d9a50dac ("ftrace: Add ftrace_lookup_symbols function")
Signed-off-by: Jiri Olsa <[email protected]>
---
kernel/trace/ftrace.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 674add0aafb3..ee9260ee0b80 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7984,15 +7984,23 @@ static int kallsyms_callback(void *data, const char *name,
struct module *mod, unsigned long addr)
{
struct kallsyms_data *args = data;
+ const char **sym;
+ int idx;

- if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp))
+ sym = bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp);
+ if (!sym)
+ return 0;
+
+ idx = sym - args->syms;
+ if (args->addrs[idx])
return 0;

addr = ftrace_location(addr);
if (!addr)
return 0;

- args->addrs[args->found++] = addr;
+ args->addrs[idx] = addr;
+ args->found++;
return args->found == args->cnt ? 1 : 0;
}

@@ -8017,6 +8025,7 @@ int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *a
struct kallsyms_data args;
int err;

+ memset(addrs, 0, sizeof(*addrs) * cnt);
args.addrs = addrs;
args.syms = sorted_syms;
args.cnt = cnt;
--
2.35.3