This patch tries to make printk more readable and reliable.
Base 16 number printing used digits[33] instead of the more readable 'x' for the "0x" prefix. That means you have to look up an array just to find out what the code does. Change it.
We already write "<NULL>" if printk gets a NULL pointer as string argument. Introduce "<almost NULL>" for string arguments with addresses below 0x400. This error happened in the past when dereferencing a struct member with a string and the struct had the address NULL.
Check if all to-be-printed characters in the string are indeed printable. The idea is to catch garbage strings from stray pointers and print "<GARBAGE>" instead. This is the only part of the patch I'm not so sure about. If a string contains characters outside classic ASCII printable stuff, this will trigger. An example would be characters with diacritic marks like äöüéăçőč. Then again, I don't see localized versions of coreboot on the horizon. Maybe for payloads, but not for coreboot itself.
Signed-off-by: Carl-Daniel Hailfinger c-d.hailfinger.devel.2006@gmx.net
Index: corebootv3-printk_safe_strings/lib/vtxprintf.c =================================================================== --- corebootv3-printk_safe_strings/lib/vtxprintf.c (Revision 1157) +++ corebootv3-printk_safe_strings/lib/vtxprintf.c (Arbeitskopie) @@ -16,6 +16,7 @@ #define isdigit(c) ((c) >= '0' && (c) <= '9') #define is_digit isdigit #define isxdigit(c) (((c) >= '0' && (c) <= '9') || ((c) >= 'a' && (c) <= 'f') || ((c) >= 'A' && (c) <= 'F')) +#define isprint(c) ((c) == '\n' || ((c) >= ' ' && (c) <= '~'))
static int skip_atoi(const char **s) { @@ -87,7 +88,7 @@ tx_byte('0', arg), count++; else if (base==16) { tx_byte('0', arg), count++; - tx_byte(digits[33], arg), count++; + tx_byte('x', arg), count++; } } if (!(type & LEFT)) @@ -194,9 +195,15 @@ s = va_arg(args, char *); if (!s) s = "<NULL>"; + /* Catch almost-NULL pointers as well */ + if ((size_t)s < 0x400) + s = "<almost NULL>";
len = strnlen(s, precision);
+ for (i = 0; i < len; ++i) + if (!isprint(*s[i])) + s = "<GARBAGE>"; if (!(flags & LEFT)) while (len < field_width--) tx_byte(' ', arg), count++;