* [PATCH 3/4] linux_inet_diag: get rid of alloca usage
2023-06-11 21:33 6% [PATCH 0/4] minor modernizations and cleanups Eric Wong
@ 2023-06-11 21:33 7% ` Eric Wong
0 siblings, 0 replies; 2+ results
From: Eric Wong @ 2023-06-11 21:33 UTC (permalink / raw)
To: raindrops-public
alloca makes stack usage unpredictable and life difficult for
static analysis tools and compilers. The 46 bytes of
INET6_ADDRSTRLEN is fine to keep on stack, but page size can be
several MB large in some architectures (but typically 4K on
common architectures).
Thus we handle page size-ed allocations via `rb_str_tmp_new'.
`rb_str_tmp_new' has been in public Ruby headers since the 1.9
days and used by the core `zlib', `digest', and `zlib'
extensions, so it should be safe to use (and `rb_str_resize' is
used in many more C extensions).
---
ext/raindrops/linux_inet_diag.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/ext/raindrops/linux_inet_diag.c b/ext/raindrops/linux_inet_diag.c
index e1ae62a..2d4f503 100644
--- a/ext/raindrops/linux_inet_diag.c
+++ b/ext/raindrops/linux_inet_diag.c
@@ -212,24 +212,25 @@ static void bug_warn_nogvl(const char *fmt, ...)
static struct listen_stats *stats_for(st_table *table, struct inet_diag_msg *r)
{
char *host, *key, *port, *old_key;
- size_t alloca_len;
struct listen_stats *stats;
socklen_t hostlen;
socklen_t portlen = (socklen_t)sizeof("65535");
int n;
const void *src = r->id.idiag_src;
+ char buf[INET6_ADDRSTRLEN];
+ size_t buf_len;
switch (r->idiag_family) {
case AF_INET: {
hostlen = INET_ADDRSTRLEN;
- alloca_len = hostlen + portlen;
- host = key = alloca(alloca_len);
+ buf_len = hostlen + portlen;
+ host = key = buf;
break;
}
case AF_INET6: {
hostlen = INET6_ADDRSTRLEN;
- alloca_len = 1 + hostlen + 1 + portlen;
- key = alloca(alloca_len);
+ buf_len = 1 + hostlen + 1 + portlen;
+ key = buf;
host = key + 1;
break;
}
@@ -269,7 +270,7 @@ static struct listen_stats *stats_for(st_table *table, struct inet_diag_msg *r)
old_key = key;
if (r->idiag_state == TCP_ESTABLISHED) {
- n = snprintf(key, alloca_len, "%s:%u",
+ n = snprintf(key, buf_len, "%s:%u",
addr_any(r->idiag_family),
ntohs(r->id.idiag_sport));
if (n <= 0) {
@@ -615,7 +616,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
{
VALUE rv = rb_hash_new();
struct nogvl_args args;
- VALUE addrs, sock;
+ VALUE addrs, sock, buf;
rb_scan_args(argc, argv, "02", &addrs, &sock);
@@ -624,8 +625,9 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
* buffer for recvmsg() later, we already checked for
* OPLEN <= page_size at initialization
*/
+ buf = rb_str_buf_new(page_size);
args.iov[2].iov_len = OPLEN;
- args.iov[2].iov_base = alloca(page_size);
+ args.iov[2].iov_base = RSTRING_PTR(buf);
args.table = NULL;
sock = NIL_P(sock) ? rb_funcall(cIDSock, id_new, 0)
: rb_io_get_io(sock);
@@ -672,6 +674,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
rb_hash_foreach(rv, drop_placeholders, Qfalse);
/* let GC deal with corner cases */
+ rb_str_resize(buf, 0);
if (argc < 2) rb_io_close(sock);
return rv;
}
^ permalink raw reply related [relevance 7%]
* [PATCH 0/4] minor modernizations and cleanups
@ 2023-06-11 21:33 6% Eric Wong
2023-06-11 21:33 7% ` [PATCH 3/4] linux_inet_diag: get rid of alloca usage Eric Wong
0 siblings, 1 reply; 2+ results
From: Eric Wong @ 2023-06-11 21:33 UTC (permalink / raw)
To: raindrops-public
alloca use was dangerous for architectures with >4K pages,
and we can avoid some Ruby #to_io dispatches in some places.
Eric Wong (4):
avoid unnecessary #to_io calls
my_fileno: use rb_io_check_closed for Ruby <3.1
linux_inet_diag: get rid of alloca usage
test_linux_reuseport_tcp_listen_stats: skip w/o unicorn
ext/raindrops/linux_inet_diag.c | 23 +++++++++++--------
ext/raindrops/my_fileno.h | 16 ++++---------
ext/raindrops/tcp_info.c | 2 +-
test/test_linux_reuseport_tcp_listen_stats.rb | 2 +-
4 files changed, 20 insertions(+), 23 deletions(-)
^ permalink raw reply [relevance 6%]
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