@@ -166,23 +166,38 @@ __uml_setup("quiet", quiet_cmd_param,
"quiet\n"
" Turns off information messages during boot.\n\n");
+/*
+ * The os_info/os_warn functions will be called by helper threads. These
+ * have a very limited stack size and using the libc formatting functions
+ * may overflow the stack.
+ * So pull in the kernel vscnprintf and use that instead with a fixed
+ * on-stack buffer.
+ */
+int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
+
void os_info(const char *fmt, ...)
{
+ char buf[256];
va_list list;
+ int len;
if (quiet_info)
return;
va_start(list, fmt);
- vfprintf(stderr, fmt, list);
+ len = vscnprintf(buf, sizeof(buf), fmt, list);
+ fwrite(buf, len, 1, stderr);
va_end(list);
}
void os_warn(const char *fmt, ...)
{
+ char buf[256];
va_list list;
+ int len;
va_start(list, fmt);
- vfprintf(stderr, fmt, list);
+ len = vscnprintf(buf, sizeof(buf), fmt, list);
+ fwrite(buf, len, 1, stderr);
va_end(list);
}
The threads allocated inside the kernel have only a single page of stack. Unfortunately, the vfprintf function in standard glibc may use too much stack-space, overflowing it. To make os_info safe to be used by helper threads, use the kernel vscnprintf function into a smallish buffer and write out the information to stderr. Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net> --- arch/um/os-Linux/util.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)