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Add a validbcd() routine that uses the bcd2bin_data[] array and returns a

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bool indicating whether the input value represents a valid BCD byte.

The existing bcd2bin() routine will KASSERT if asked to convert a bad value,
but sometimes the kernel has to handle BCD data from untrusted sources, so
this will provide a mechanism to validate data before attempting conversion.

This would be have easier/cleaner if the bcd2bin_data[] array contained an
out-of-range value (such as 0xff) in the infill locations that aren't valid,
but it's a global symbol that might be referenced by out-of-tree code
relying on the current scheme, so I'm leaving that alone.
This commit is contained in:
ian 2017-12-31 22:43:24 +00:00
parent 73ace5c469
commit 97b17432b4
2 changed files with 8 additions and 0 deletions
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1
stand/libsa/stand.h
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@ -354,6 +354,7 @@ extern char const hex2ascii_data[];
#define bcd2bin(bcd) (bcd2bin_data[bcd])
#define bin2bcd(bin) (bin2bcd_data[bin])
#define hex2ascii(hex) (hex2ascii_data[hex])
#define validbcd(bcd) (bcd == 0 || (bcd > 0 && bcd <= 0x99 && bcd2bin_data[bcd] != 0))
/* min/max (undocumented) */
static __inline int imax(int a, int b) { return (a > b ? a : b); }

7
sys/sys/libkern.h
View File

@ -82,6 +82,13 @@ hex2ascii(int hex)
return (hex2ascii_data[hex]);
}
static inline bool
validbcd(int bcd)
{
return (bcd == 0 || (bcd > 0 && bcd <= 0x99 && bcd2bin_data[bcd] != 0));
}
static __inline int imax(int a, int b) { return (a > b ? a : b); }
static __inline int imin(int a, int b) { return (a < b ? a : b); }
static __inline long lmax(long a, long b) { return (a > b ? a : b); }