MINOR: debug: add ability to dump loaded shared libraries
Many times core dumps reported by users who experience trouble are
difficult to exploit due to missing system libraries. Sometimes,
having just a list of loaded libraries and their respective addresses
can already provide some hints about some problems.
This patch makes a step in that direction by adding a new "show libs"
command that will try to enumerate the list of object files that are
loaded in memory, relying on the dynamic linker for this. It may also
be used to detect that some foreign code embarks other undesired libs
(e.g. some external Lua modules).
At the moment it's only supported on glibc when USE_DL is set, but it's
implemented in a way that ought to make it reasonably easy to be extended
to other platforms.
diff --git a/src/tools.c b/src/tools.c
index 5d8483d..c60f80b 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -4983,6 +4983,96 @@
return NULL;
}
+/* On systems where this is supported, let's provide a possibility to enumerate
+ * the list of object files. The output is appended to a buffer initialized by
+ * the caller, with one name per line. A trailing zero is always emitted if data
+ * are written. Only real objects are dumped (executable and .so libs). The
+ * function returns non-zero if it dumps anything. These functions do not make
+ * use of the trash so that it is possible for the caller to call them with the
+ * trash on input. The output format may be platform-specific but at least one
+ * version must emit raw object file names when argument is zero.
+ */
+#if defined(HA_HAVE_DUMP_LIBS)
+# if defined(HA_HAVE_DL_ITERATE_PHDR)
+/* the private <data> we pass below is a dump context initialized like this */
+struct dl_dump_ctx {
+ struct buffer *buf;
+ int with_addr;
+};
+
+static int dl_dump_libs_cb(struct dl_phdr_info *info, size_t size, void *data)
+{
+ struct dl_dump_ctx *ctx = data;
+ const char *fname;
+ size_t p1, p2, beg, end;
+ int idx;
+
+ if (!info || !info->dlpi_name)
+ goto leave;
+
+ if (!*info->dlpi_name)
+ fname = get_exec_path();
+ else if (strchr(info->dlpi_name, '/'))
+ fname = info->dlpi_name;
+ else
+ /* else it's a VDSO or similar and we're not interested */
+ goto leave;
+
+ if (!ctx->with_addr)
+ goto dump_name;
+
+ /* virtual addresses are relative to the load address and are per
+ * pseudo-header, so we have to scan them all to find the furthest
+ * one from the beginning. In this case we only dump entries if
+ * they have at least one section.
+ */
+ beg = ~0; end = 0;
+ for (idx = 0; idx < info->dlpi_phnum; idx++) {
+ if (!info->dlpi_phdr[idx].p_memsz)
+ continue;
+ p1 = info->dlpi_phdr[idx].p_vaddr;
+ if (p1 < beg)
+ beg = p1;
+ p2 = p1 + info->dlpi_phdr[idx].p_memsz - 1;
+ if (p2 > end)
+ end = p2;
+ }
+
+ if (!idx)
+ goto leave;
+
+ chunk_appendf(ctx->buf, "0x%012llx-0x%012llx (0x%07llx) ",
+ (ullong)info->dlpi_addr + beg,
+ (ullong)info->dlpi_addr + end,
+ (ullong)(end - beg + 1));
+ dump_name:
+ chunk_appendf(ctx->buf, "%s\n", fname);
+ leave:
+ return 0;
+}
+
+/* dumps lib names and optionally address ranges */
+int dump_libs(struct buffer *output, int with_addr)
+{
+ struct dl_dump_ctx ctx = { .buf = output, .with_addr = with_addr };
+ size_t old_data = output->data;
+
+ dl_iterate_phdr(dl_dump_libs_cb, &ctx);
+ return output->data != old_data;
+}
+# else // no DL_ITERATE_PHDR
+# error "No dump_libs() function for this platform"
+# endif
+#else // no HA_HAVE_DUMP_LIBS
+
+/* unsupported platform: do not dump anything */
+int dump_libs(struct buffer *output, int with_addr)
+{
+ return 0;
+}
+
+#endif // HA_HAVE_DUMP_LIBS
+
/*
* Allocate an array of unsigned int with <nums> as address from <str> string
* made of integer separated by dot characters.