CPU Identification For OS Developers...

[Brynet-Inc]

Recently when working on a OS-Dev project I wrote code for detecting both AMD and Intel 32bit x86 CPU's, The code is written in C(with one line of inline asm..) and compiles in GCC with with OS-Dev projects in mind.

Features
Detects basically every x86 cpu supporting the CPUID instruction.
Supports 386/486 CPU's with CPUID (There are a few..)

Supports The following CPU's..
Intel 486/586/686 and compatible AMD CPU's..
Also supports Pentium Pro/Pentium 1/2/3/4 and later AMD models including Athlon,Duron,Athlon MP/Mobile, K6, K6-2, K6-III, and early K5's..

Example Output on an Athlon XP 2600+
AMD-specific functions
Family: 6 Model: 10 [Duron/Athlon model 10]
Detected Processor Name: AMD Athlon(TM) XP 2600+

Only has 1 external dependency! requires a fairly(ish) compliant printf, Decimal and String support like %s and %d and this is truly all you need!


Comments/Questions? Death Threats? Post them here

(All under the BSD license so feel free to use this in your closed source OS also..)

[Habbit]

Well, I haven't had time to test it, but I must say it looks like quite a good and thorough job. Keep it up!

[piranha]

Wow! That works great!
All I had to do was adapt it for my prinf() function, then it worked without problems! ;D

[Brynet-Inc]

Wow! That works great!
All I had to do was adapt it for my prinf() function, then it worked without problems! ;D

I'm very glad it worked out for you, Enjoy it.

[Candamir]

Looks like a fine piece of code. Nice job!

Candamir

[Shecks]

Hi,

First off, nice piece of code.

There might be a little potential bug there though. I notice in detect_cpu() you declare an unsigned long 'maxi' and pass it to both do_intel() and do_amd() but it is never initailised (unless i've missed something) . Both sub functions test maxi for >= 1 but it is never explicitly set?

Is this a typo? or am i loosing the plot :-\

Shecks

[Brynet-Inc]

Hi,

First off, nice piece of code.

There might be a little potential bug there though. I notice in detect_cpu() you declare an unsigned long 'maxi' and pass it to both do_intel() and do_amd() but it is never initailised (unless i've missed something) . Both sub functions test maxi for >= 1 but it is never explicitly set?

Is this a typo? or am i loosing the plot :-\

Shecks

Yes, Sorry, Thanks for pointing this out, The codebase used to be much larger and that variable was actually used for something at one time ::).

[proxy]

generally a good piece of code, and a solid example of how to properly detect CPU types and such.

Now here's come the nit-picking

Control reaches the end of several functions defined to return int.

A few funtions are defined to return int for no apparent reason (some of these overlap with the ones which reach the end with no return!)

some functions (int do_intel and int do_amd) are used before the defintion in the file, which is technically ok in c89, but produces an avoidable warning.

finally, the integer constant 0x80000002 is unsigned but being used in a for loop where j is signed, thus you get an avoidable warning involving comparison of signed/unsigned comparison mis-match.

like i said, good code overall, just had to get out my pedantic side for a bit

good job

proxy

[Brynet-Inc]

generally a good piece of code, and a solid example of how to properly detect CPU types and such.

Now here's come the nit-picking

Control reaches the end of several functions defined to return int.

A few funtions are defined to return int for no apparent reason (some of these overlap with the ones which reach the end with no return!)

some functions (int do_intel and int do_amd) are used before the defintion in the file, which is technically ok in c89, but produces an avoidable warning.

finally, the integer constant 0x80000002 is unsigned but being used in a for loop where j is signed, thus you get an avoidable warning involving comparison of signed/unsigned comparison mis-match.

like i said, good code overall, just had to get out my pedantic side for a bit

good job

proxy

Thanks for the criticism and the compliments , I'm generally a bad at keeping with whats standard C89 and C99, But from my POV I don't get any errors, or warnings, So I'm happy as a clam.



Take care, And Thanks again.

[proxy]

if you are not getting warnings in with this code, then you are not compiling with a reasonable warning level. gcc you shoudl be using "-Wall" (preferably "-W -Wall" if you wanna be extra strict), and in msvc you should be using something like warning level 3 for decent useful warnings.

every compiler worth using will warn about code like this:

Code: Select all

int f() {
}

because it is declared as returning an int, but there is no actual return statement.

proxy

[srg_13]

Looks pretty cool. I'll have to try it out!

Thanks,

-Stephen

[Brynet-Inc]

if you are not getting warnings in with this code, then you are not compiling with a reasonable warning level. gcc you shoudl be using "-Wall" (preferably "-W -Wall" if you wanna be extra strict), and in msvc you should be using something like warning level 3 for decent useful warnings.

every compiler worth using will warn about code like this:

Code: Select all

int f() {
}

because it is declared as returning an int, but there is no actual return statement.

proxy

Alright, Alright, I made some cleanup's, Hopefully this is acceptable , Compiles with no warnings/errors with -Wall and -W.

Thanks Again

[smiddy]

Here's what I get with C++ 6.0:

Code: Select all

Deleting intermediate files and output files for project 'cpudet-fix - Win32 Debug'.
--------------------Configuration: cpudet-fix - Win32 Debug--------------------
Compiling...
cpudet-fix.c
c:\smiddyos\cpuid c\cpudet-fix.c(55) : warning C4013: 'asm' undefined; assuming extern returning int
c:\smiddyos\cpuid c\cpudet-fix.c(55) : error C2143: syntax error : missing ')' before ':'
c:\smiddyos\cpuid c\cpudet-fix.c(65) : warning C4013: 'printf' undefined; assuming extern returning int
c:\smiddyos\cpuid c\cpudet-fix.c(75) : error C2143: syntax error : missing ';' before 'type'
c:\smiddyos\cpuid c\cpudet-fix.c(76) : error C2143: syntax error : missing ';' before 'type'
c:\smiddyos\cpuid c\cpudet-fix.c(77) : error C2143: syntax error : missing ';' before 'type'
c:\smiddyos\cpuid c\cpudet-fix.c(78) : error C2143: syntax error : missing ')' before ':'
c:\smiddyos\cpuid c\cpudet-fix.c(79) : error C2065: 'stepping' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(79) : error C2065: 'eax' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(80) : error C2065: 'model' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(81) : error C2065: 'family' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(82) : error C2065: 'type' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(83) : error C2065: 'reserved' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(122) : error C2065: 'extended_family' : undeclared identifier
c:\smiddyos\cpuid c\cpudet-fix.c(228) : error C2143: syntax error : missing ';' before 'type'
c:\smiddyos\cpuid c\cpudet-fix.c(229) : error C2143: syntax error : missing ';' before 'type'
c:\smiddyos\cpuid c\cpudet-fix.c(230) : error C2143: syntax error : missing ')' before ':'
c:\smiddyos\cpuid c\cpudet-fix.c(287) : error C2143: syntax error : missing ')' before ':'
c:\smiddyos\cpuid c\cpudet-fix.c(299) : error C2143: syntax error : missing ')' before ':'
Error executing cl.exe.

cpudet-fix.exe - 17 error(s), 2 warning(s)

[oswizard]

The code uses GCC-specific assembly language syntax. You will probably need to redefine the asm macro.

[Brynet-Inc]

Yeah smiddy, I use OpenBSD and if you can see from my signature I do not care for Windows, This is for OSdev projects..It should compile safely in MinGW/GCC if you absolutely have to compile it in Windows, But I never recommend using Windows for anything at all, ;D

Definitely not meant for usage in MSVC pal, Why anyone would want to use MSVC for OS Development is beyond me.. ::)