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

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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.
This commit is contained in:
Carlos Eduardo Seo 2022-07-07 18:46:43 +00:00 committed by Szabolcs Nagy
parent cec148df6f
commit 3be82efc58
4 changed files with 141 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
stdio-common/printf-parsemb.c
View File

@ -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;

3
stdio-common/printf.h
View File

@ -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. */
};

13
stdio-common/vfprintf-internal.c
View File

@ -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;

121
stdio-common/vfprintf-process-arg.c
View File

@ -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');