Currently the string functions grub_strtol(), grub_strtoul(), and
grub_strtoull() don't declare the "end" pointer in such a way as to
require the pointer itself or the character array to be immutable to the
implementation, nor does the C standard do so in its similar functions,
though it does require us not to change any of it.
The typical declarations of these functions follow this pattern:
long
strtol(const char * restrict nptr, char ** restrict endptr, int base);
Much of the reason for this is historic, and a discussion of that
follows below, after the explanation of this change. (GRUB currently
does not include the "restrict" qualifiers, and we name the arguments a
bit differently.)
The implementation is semantically required to treat the character array
as immutable, but such accidental modifications aren't stopped by the
compiler, and the semantics for both the callers and the implementation
of these functions are sometimes also helped by adding that requirement.
This patch changes these declarations to follow this pattern instead:
long
strtol(const char * restrict nptr,
const char ** const restrict endptr,
int base);
This means that if any modification to these functions accidentally
introduces either an errant modification to the underlying character
array, or an accidental assignment to endptr rather than *endptr, the
compiler should generate an error. (The two uses of "restrict" in this
case basically mean strtol() isn't allowed to modify the character array
by going through *endptr, and endptr isn't allowed to point inside the
array.)
It also means the typical use case changes to:
char *s = ...;
const char *end;
long l;
l = strtol(s, &end, 10);
Or even:
const char *p = str;
while (p && *p) {
long l = strtol(p, &p, 10);
...
}
This fixes 26 places where we discard our attempts at treating the data
safely by doing:
const char *p = str;
long l;
l = strtol(p, (char **)&ptr, 10);
It also adds 5 places where we do:
char *p = str;
while (p && *p) {
long l = strtol(p, (const char ** const)&p, 10);
...
/* more calls that need p not to be pointer-to-const */
}
While moderately distasteful, this is a better problem to have.
With one minor exception, I have tested that all of this compiles
without relevant warnings or errors, and that /much/ of it behaves
correctly, with gcc 9 using 'gcc -W -Wall -Wextra'. The one exception
is the changes in grub-core/osdep/aros/hostdisk.c , which I have no idea
how to build.
Because the C standard defined type-qualifiers in a way that can be
confusing, in the past there's been a slow but fairly regular stream of
churn within our patches, which add and remove the const qualifier in many
of the users of these functions. This change should help avoid that in
the future, and in order to help ensure this, I've added an explanation
in misc.h so that when someone does get a compiler warning about a type
error, they have the fix at hand.
The reason we don't have "const" in these calls in the standard is
purely anachronistic: C78 (de facto) did not have type qualifiers in the
syntax, and the "const" type qualifier was added for C89 (I think; it
may have been later). strtol() appears to date from 4.3BSD in 1986,
which means it could not be added to those functions in the standard
without breaking compatibility, which is usually avoided.
The syntax chosen for type qualifiers is what has led to the churn
regarding usage of const, and is especially confusing on string
functions due to the lack of a string type. Quoting from C99, the
syntax is:
declarator:
pointer[opt] direct-declarator
direct-declarator:
identifier
( declarator )
direct-declarator [ type-qualifier-list[opt] assignment-expression[opt] ]
...
direct-declarator [ type-qualifier-list[opt] * ]
...
pointer:
* type-qualifier-list[opt]
* type-qualifier-list[opt] pointer
type-qualifier-list:
type-qualifier
type-qualifier-list type-qualifier
...
type-qualifier:
const
restrict
volatile
So the examples go like:
const char foo; // immutable object
const char *foo; // mutable pointer to object
char * const foo; // immutable pointer to mutable object
const char * const foo; // immutable pointer to immutable object
const char const * const foo; // XXX extra const keyword in the middle
const char * const * const foo; // immutable pointer to immutable
// pointer to immutable object
const char ** const foo; // immutable pointer to mutable pointer
// to immutable object
Making const left-associative for * and right-associative for everything
else may not have been the best choice ever, but here we are, and the
inevitable result is people using trying to use const (as they should!),
putting it at the wrong place, fighting with the compiler for a bit, and
then either removing it or typecasting something in a bad way. I won't
go into describing restrict, but its syntax has exactly the same issue
as with const.
Anyway, the last example above actually represents the *behavior* that's
required of strtol()-like functions, so that's our choice for the "end"
pointer.
Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The following are two use cases from Rajat Jain <rajatjain@juniper.net>:
1) We have a board that boots Linux and this board itself can be plugged
into one of different chassis types. We need to pass different
parameters to the kernel based on the "CHASSIS_TYPE" information
that is passed by the bios in the DMI/SMBIOS tables.
2) We may have a USB stick that can go into multiple boards, and the
exact kernel to be loaded depends on the machine information
(PRODUCT_NAME etc) passed via the DMI.
Signed-off-by: David Michael <fedora.dm0@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
In order to be able to read from and write to model-specific registers,
two new modules are added. They are i386 specific, as the cpuid module.
rdmsr module registers the command rdmsr that allows reading from a MSR.
wrmsr module registers the command wrmsr that allows writing to a MSR.
wrmsr module is disabled if UEFI secure boot is enabled.
Please note that on SMP systems, interacting with a MSR that has a scope
per hardware thread, implies that the value only applies to the
particular cpu/core/thread that ran the command.
Also, if you specify a reserved or unimplemented MSR address, it will
cause a general protection exception (which is not currently being
handled) and the system will reboot.
Signed-off-by: Jesús Diéguez Fernández <jesusdf@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Let's provide file type info to the I/O layer. This way verifiers
framework and its users will be able to differentiate files and verify
only required ones.
This is preparatory patch.
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
PIT isn't available on some of new hardware including Hyper-V. So
use pmtimer for calibration. Moreover pmtimer calibration is faster, so
use it on coreboor where booting time is important.
Based on patch by Michael Chang.
Add the descriptions of the “core”, that means no vendorcode or payload,
coreboot time stamps added up to coreboot commit a7d92441 (timestamps:
You can never have enough of them!) [1].
Running `coreboot_boottime` in the GRUB command line interface now shows
descriptions for all time stamps again on the ASRock E350M1.
[1] http://review.coreboot.org/9608
EBDA layout is not standardized so we cannot assume first two bytes
are length. Neither is it required by ACPI standard. HP 8710W is known
to contain zeroes here.
Closes: 45002
"Command for ...".
* grub-core/commands/hdparm.c (options): Use "Display" rather than
"Check" since we don't check anything.
* grub-core/commands/i386/cpuid.c (options): Clarify that long mode
is 64-bit one.
* grub-core/commands/search_wrap.c (options): Clarify the conditions.
* grub-core/disk/geli.c (grub_md_sha256_real): Fix typo.
(grub_md_sha512_real): Likewise.
