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Fix stack overflow when serving http files on ESP8266

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ESP8266 non-OS has very limited stack - only 4K. Undetected stack
overflows cause nasty bugs and it turns out serving files over http
routinely causes stack overflow.

This was exposed by https://github.com/cesanta/mongoose-os/commit/a5f59123edcfef10c351b3e679f28720b5de9611

As a short-term workaround, push http_message into bss, this is enough
as an immediate workaround. Longer term, we need to think how to bring
8266 to parity with other platforms where we have at least 8K stack.

At the same time, get rid of the compiler bug workaround - modern
toolchain doesn't need this.
This commit is contained in:
Deomid "rojer" Ryabkov authored and Deomid Ryabkov committed 2021-06-12 00:30:51 +01:00
1 parent d6c9d3c181
commit 70034b5873
2 files changed
+16 -42
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mongoose.c
+8 -21
View File
@@ -6395,30 +6395,17 @@ static void deliver_chunk(struct mg_connection *c, struct http_message *hm,
}
}
/*
* lx106 compiler has a bug (TODO(mkm) report and insert tracking bug here)
* If a big structure is declared in a big function, lx106 gcc will make it
* even bigger (round up to 4k, from 700 bytes of actual size).
*/
#ifdef __xtensa__
static void mg_http_handler2(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data),
struct http_message *hm) __attribute__((noinline));
void mg_http_handler(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data)) {
struct http_message hm;
mg_http_handler2(nc, ev, ev_data MG_UD_ARG(user_data), &hm);
}
static void mg_http_handler2(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data),
struct http_message *hm) {
#else /* !__XTENSA__ */
void mg_http_handler(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data)) {
/* On ESP8266 stack is especially limited (4K).
* Since Mongoose is single-threaded, we can use the same struct
* and save ~400 bytes. This may not seem like much but in fact it's the
* difference between overflowing and not (when serving files). */
#if CS_PLATFORM == CS_P_ESP8266
static struct http_message shm, *hm = &shm;
#else
struct http_message shm, *hm = &shm;
#endif /* __XTENSA__ */
#endif
struct mg_http_proto_data *pd = mg_http_get_proto_data(nc);
struct mbuf *io = &nc->recv_mbuf;
int req_len;
src/mg_http.c
+8 -21
View File
@@ -740,30 +740,17 @@ static void deliver_chunk(struct mg_connection *c, struct http_message *hm,
}
}
/*
* lx106 compiler has a bug (TODO(mkm) report and insert tracking bug here)
* If a big structure is declared in a big function, lx106 gcc will make it
* even bigger (round up to 4k, from 700 bytes of actual size).
*/
#ifdef __xtensa__
static void mg_http_handler2(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data),
struct http_message *hm) __attribute__((noinline));
void mg_http_handler(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data)) {
struct http_message hm;
mg_http_handler2(nc, ev, ev_data MG_UD_ARG(user_data), &hm);
}
static void mg_http_handler2(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data),
struct http_message *hm) {
#else /* !__XTENSA__ */
void mg_http_handler(struct mg_connection *nc, int ev,
void *ev_data MG_UD_ARG(void *user_data)) {
/* On ESP8266 stack is especially limited (4K).
* Since Mongoose is single-threaded, we can use the same struct
* and save ~400 bytes. This may not seem like much but in fact it's the
* difference between overflowing and not (when serving files). */
#if CS_PLATFORM == CS_P_ESP8266
static struct http_message shm, *hm = &shm;
#else
struct http_message shm, *hm = &shm;
#endif /* __XTENSA__ */
#endif
struct mg_http_proto_data *pd = mg_http_get_proto_data(nc);
struct mbuf *io = &nc->recv_mbuf;
int req_len;