cheri: stdio-common: add support for printing CHERI capabilities

This adds a new modifier %#p for printing capability information
according to the CHERI C Programming guide:

https://github.com/CTSRD-CHERI/cheri-c-programming/wiki/Displaying-Capabilities

A %#p option in printf will display:

  <address> [<permissions>,<base>-<top>] (<attr>)

   * address: Virtual address of capability displayed as a hexadecimal
     value with a 0x prefix.
   * permissions: Zero or more of the following characters:
      r: LOAD permission
      w: STORE permission
      x: EXECUTE permission
      R: LOAD_CAP permission
      W: STORE_CAP permission
      E: EXECUTIVE permission (Morello only)
   * base: Lower bound of capability displayed as a hexadecimal value
     with a 0x prefix.
   * top: Upper bound of capability plus 1 displayed as a hexadecimal
     value with a 0x prefix.
   * attr: Zero or more of the following comma-separated attributes. If
     none of the attributes are present, this field is omitted (along
     with the enclosing parentheses/brackets).
      invalid: Capability's tag is clear.
      sentry: Capability is a sealed entry.
      sealed: Capability is sealed with a type other than the sealed
              entry object type.

A %p option in printf will display the capability value (address) normally.

diff --git a/stdio-common/printf-parsemb.c b/stdio-common/printf-parsemb.c
index 386e2a27bb6a3512b599dbab29d64216a0e41b36..e9e395c2deb988eca43ff14b9337fae8d83d76be 100644 (file)
--- a/stdio-common/printf-parsemb.c
+++ b/stdio-common/printf-parsemb.c
@@ -80,6 +80,7 @@ __parse_one_specmb (const UCHAR_T *format, size_t posn,
   spec->info.pad = ' ';
   spec->info.wide = sizeof (UCHAR_T) > 1;
   spec->info.is_binary128 = 0;
+  spec->info.is_cap = 0;
 
   /* Test for positional argument.  */
   if (ISDIGIT (*format))
@@ -371,6 +372,10 @@ __parse_one_specmb (const UCHAR_T *format, size_t posn,
          break;
        case L'p':
          spec->data_arg_type = PA_POINTER;
+#ifdef __CHERI_PURE_CAPABILITY__
+         if (spec->info.alt)
+           spec->info.is_cap = 1;
+#endif
          break;
        case L'n':
          spec->data_arg_type = PA_INT|PA_FLAG_PTR;

diff --git a/stdio-common/printf.h b/stdio-common/printf.h
index 46993e031e178fd6baa0149731f58773452b46e2..815dc95779e3da1229a58ebf50c7eed7ec9a4588 100644 (file)
--- a/stdio-common/printf.h
+++ b/stdio-common/printf.h
@@ -50,7 +50,8 @@ struct printf_info
   unsigned int i18n:1;         /* I flag.  */
   unsigned int is_binary128:1; /* Floating-point argument is ABI-compatible
                                   with IEC 60559 binary128.  */
-  unsigned int __pad:3;                /* Unused so far.  */
+  unsigned int is_cap:1;       /* CHERI capability.  */
+  unsigned int __pad:2;                /* Unused so far.  */
   unsigned short int user;     /* Bits for user-installed modifiers.  */
   wchar_t pad;                 /* Padding character.  */
 };

diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
index fb94961f37265940b19f909901a10d89672988e9..6bda3a2b278c6ea40f66f7a69aed8635b160d660 100644 (file)
--- a/stdio-common/vfprintf-internal.c
+++ b/stdio-common/vfprintf-internal.c
@@ -116,6 +116,10 @@
   while (0)
 #endif
 
+#ifdef __CHERI_PURE_CAPABILITY__
+# include <cheri_perms.h>
+#endif
+
 /* Add LENGTH to DONE.  Return the new value of DONE, or -1 on
    overflow (and set errno accordingly).  */
 static inline int
@@ -792,6 +796,9 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap, unsigned int mode_flags)
       int base;
       union printf_arg the_arg;
       CHAR_T *string;  /* Pointer to argument string.  */
+#ifdef __CHERI_PURE_CAPABILITY__
+      const void *cap = 0;
+#endif
       int alt = 0;     /* Alternate format.  */
       int space = 0;   /* Use space prefix if no sign is needed.  */
       int left = 0;    /* Left-justify output.  */
@@ -805,6 +812,8 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap, unsigned int mode_flags)
       int is_char = 0; /* Argument is promoted (unsigned) char.  */
       int width = 0;   /* Width of output; 0 means none specified.  */
       int prec = -1;   /* Precision of output; -1 means none specified.  */
+      int is_cap = 0;  /* Argument is a capability.  */
+
       /* This flag is set by the 'I' modifier and selects the use of the
         `outdigits' as determined by the current locale.  */
       int use_outdigits = 0;
@@ -1324,6 +1333,9 @@ printf_positional (FILE *s, const CHAR_T *format, int readonly_format,
       } number;
       int base;
       CHAR_T *string;          /* Pointer to argument string.  */
+#ifdef __CHERI_PURE_CAPABILITY__
+      const void *cap = 0;
+#endif
 
       /* Fill variables from values in struct.  */
       int alt = specs[nspecs_done].info.alt;
@@ -1338,6 +1350,7 @@ printf_positional (FILE *s, const CHAR_T *format, int readonly_format,
       int is_long = specs[nspecs_done].info.is_long;
       int width = specs[nspecs_done].info.width;
       int prec = specs[nspecs_done].info.prec;
+      int is_cap = specs[nspecs_done].info.is_cap;
       int use_outdigits = specs[nspecs_done].info.i18n;
       char pad = specs[nspecs_done].info.pad;
       CHAR_T spec = specs[nspecs_done].info.spec;

diff --git a/stdio-common/vfprintf-process-arg.c b/stdio-common/vfprintf-process-arg.c
index 4fe369e111692da13b04115792543fe75424d68f..709d2c7db7cb11b06cf85c50692ad93820778e6e 100644 (file)
--- a/stdio-common/vfprintf-process-arg.c
+++ b/stdio-common/vfprintf-process-arg.c
@@ -25,6 +25,115 @@
 {
   /* Start real work.  We know about all flags and modifiers and
      now process the wanted format specifier.  */
+
+/* Process capability information according to the CHERI C Programming guide:
+   https://github.com/CTSRD-CHERI/cheri-c-programming/wiki/Displaying-Capabilities */
+#ifdef __CHERI_PURE_CAPABILITY__
+LABEL (capability):
+  /* CHERI capability.  */
+  {
+       uint64_t cap_perm = 0;
+       uint64_t cap_base = 0;
+       uint64_t cap_limit = 0;
+       uint64_t cap_tag = 0;
+       uint64_t cap_type = 0;
+       outchar (L_(' '));
+       outchar (L_('['));
+       cap_perm = __builtin_cheri_perms_get (cap);
+       if (cap_perm & CAP_PERM_LOAD)
+         outchar (L_('r'));
+       if (cap_perm & CAP_PERM_STORE)
+         outchar (L_('w'));
+       if (cap_perm & CAP_PERM_EXECUTE)
+         outchar (L_('x'));
+       if (cap_perm & CAP_PERM_LOAD_CAP)
+         outchar (L_('R'));
+       if (cap_perm & CAP_PERM_STORE_CAP)
+         outchar (L_('W'));
+       if (cap_perm & CAP_PERM_EXECUTIVE)
+         outchar (L_('E'));
+       outchar (L_(','));
+       cap_base = __builtin_cheri_base_get (cap);
+       number.word = (unsigned long int) cap_base;
+       if (prec < 0)
+         prec = 1;
+       else
+         pad = L_(' ');
+       string = _itoa_word (number.word, workend, base, spec == L_('X'));
+       prec = MAX (0, prec - (workend - string));
+       width -= workend - string + prec;
+       if (number.word != 0)
+         width -= 2;
+       if (pad == L_(' '))
+         {
+           PAD (L_(' '));
+           width = 0;
+         }
+       if (number.word != 0)
+         {
+           outchar (L_('0'));
+           outchar (spec);
+         }
+       width += prec;
+       PAD (L_('0'));
+       outstring (string, workend - string);
+       outchar (L_('-'));
+       cap_limit = __builtin_cheri_length_get (cap) + cap_base;
+       number.word = (unsigned long int) cap_limit;
+       if (prec < 0)
+         prec = 1;
+       else
+         pad = L_(' ');
+       string = _itoa_word (number.word, workend, base, spec == L_('X'));
+       prec = MAX (0, prec - (workend - string));
+       width -= workend - string + prec;
+       if (number.word != 0)
+         width -= 2;
+       if (pad == L_(' '))
+         {
+           PAD (L_(' '));
+           width = 0;
+         }
+       if (number.word != 0)
+         {
+           outchar (L_('0'));
+           outchar (spec);
+         }
+       width += prec;
+       PAD (L_('0'));
+       outstring (string, workend - string);
+       outchar (L_(']'));
+       cap_tag = __builtin_cheri_tag_get (cap);
+       if (!cap_tag)
+         {
+           outchar (L_(' '));
+           outchar (L_('('));
+           outstring ("invalid", 8);
+           outchar (L_(')'));
+           break;
+         }
+       cap_type = __builtin_cheri_type_get (cap);
+       if (cap_type != 0)
+         {
+           if (cap_type == 1)
+             {
+               outchar (L_(' '));
+               outchar (L_('('));
+               outstring ("sentry", 7);
+               outchar (L_(')'));
+             }
+           else
+             {
+               outchar (L_(' '));
+               outchar (L_('('));
+               outstring ("sealed", 7);
+               outchar (L_(')'));
+             }
+         }
+      }
+      break;
+#endif
+
 LABEL (form_percent):
   /* Write a literal "%".  */
   outchar (L_('%'));
@@ -212,6 +321,11 @@ LABEL (unsigned_number):      /* Unsigned number of base BASE.  */
 
       outstring (string, workend - string);
 
+#ifdef __CHERI_PURE_CAPABILITY__
+      if (is_cap == 1)
+       goto LABEL(capability);
+#endif
+
       break;
     }
   else
@@ -265,6 +379,13 @@ LABEL (form_pointer):
         base = 16;
         number.word = (unsigned long int) ptr;
         is_negative = 0;
+#ifdef __CHERI_PURE_CAPABILITY__
+       if (alt == 1)
+         {
+           cap = ptr;
+           is_cap = 1;
+         }
+#endif
         alt = 1;
         group = 0;
         spec = L_('x');