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Site Admin  Joined: Sat Oct 20, 2007 7:58 pm Posts: 454 
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 Chapter 23 Demo ReleaseHello everyone,
Chapter 23 of the OSDev Series has been updated with some additional content and demo release. I apologize for the delay. The next chapter we will be modifying and expanding on the demo provided in this chapter while we support a user mode<>kernel mode single tasking in Chapter 24. _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com |
| Sun Oct 31, 2010 2:41 am |
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Moderator
Joined: Thu Jan 10, 2008 6:43 pm Posts: 95 Location: USA
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Re: Chapter 23 Demo Release Hooray! Thanks!!
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| Sun Oct 31, 2010 11:11 pm |
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Joined: Sun Jul 11, 2010 1:12 pm Posts: 19
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Re: Chapter 23 Demo Release The real question is, when the update for chapter 22 will be released??
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| Mon Nov 01, 2010 2:17 pm |
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Site Admin Joined: Sat Oct 20, 2007 7:58 pm Posts: 454
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Re: Chapter 23 Demo Release Hello,
The updates for Chapter 22 (and actually Chapter 23) should be this weekend. The updates are the same as with the previous demo updates however does take a bit of time to complete. _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com |
| Tue Nov 02, 2010 5:33 am |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release Hi Mike,
About chapter 23: user command causes a page fault. I'm trying to discovery the motive... Thanks _________________ _____________ Think it, build it, bit by bit... |
| Tue Nov 02, 2010 12:09 pm |
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Site Admin Joined: Sat Oct 20, 2007 7:58 pm Posts: 454
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Re: Chapter 23 Demo Release Hello,
Chapter 23 was based off of the Chapter 22 demo, both of which are in need of the bug fix update. Because these are the last two chapters in need for this update at this time, they should be updated this weekend. I suspect this might be the cause of the page fault, which appears in certain emulators (not all). _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com |
| Wed Nov 03, 2010 12:31 am |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release ...before diving into code there is a doubt.
At the moment of TSS register... should not be sizeof(tss_entry)-1 instead of base+sizeof(tss_entry)?(...at transfers, the system will pick up that struct and fill the the entire cpu context?) _________________ _____________ Think it, build it, bit by bit... |
| Wed Nov 03, 2010 8:14 am |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release last question was that so bad?
any way... it crash here (iret instruction): (goto user land procedure) Code: (0) [0x00101378] 0008:00000000c0001378 (unk. ctxt): cli ; fa (0) [0x00101379] 0008:00000000c0001379 (unk. ctxt): mov ax, 0x0023 ; 66b82300 (0) [0x0010137d] 0008:00000000c000137d (unk. ctxt): mov ds, ax ; 668ed8 (0) [0x00101380] 0008:00000000c0001380 (unk. ctxt): mov es, ax ; 668ec0 (0) [0x00101383] 0008:00000000c0001383 (unk. ctxt): mov fs, ax ; 668ee0 (0) [0x00101386] 0008:00000000c0001386 (unk. ctxt): mov gs, ax ; 668ee8 (0) [0x00101389] 0008:00000000c0001389 (unk. ctxt): push 0x00000023 ; 6a23 (0) [0x0010138b] 0008:00000000c000138b (unk. ctxt): push esp ; 54 (0) [0x0010138c] 0008:00000000c000138c (unk. ctxt): pushfd ; 9c (0) [0x0010138d] 0008:00000000c000138d (unk. ctxt): pop eax ; 58 (0) [0x0010138e] 0008:00000000c000138e (unk. ctxt): or eax, 0x00000200 ; 0d00020000 (0) [0x00101393] 0008:00000000c0001393 (unk. ctxt): push eax ; 50 (0) [0x00101394] 0008:00000000c0001394 (unk. ctxt): push 0x0000001b ; 6a1b (0) [0x00101396] 0008:00000000c0001396 (unk. ctxt): lea eax, dword ptr ds:0xc000139e ; 8d059e1300c0 (0) [0x0010139c] 0008:00000000c000139c (unk. ctxt): push eax ; 50 (0) [0x0010139d] 0008:00000000c000139d (unk. ctxt): iretd ; cf registers context (before iret) Code: rax: 0x00000000:c000139e rcx: 0x00000000:00008f1c rdx: 0x00000000:c0008bc0 rbx: 0x00000000:00000001 rsp: 0x00000000:00008f00 rbp: 0x00000000:00008f14 rsi: 0x00000000:00008fd4 rdi: 0x00000000:00000090 r8 : 0x00000000:00000000 r9 : 0x00000000:00000000 r10: 0x00000000:00000000 r11: 0x00000000:00000000 r12: 0x00000000:00000000 r13: 0x00000000:00000000 r14: 0x00000000:00000000 r15: 0x00000000:00000000 rip: 0x00000000:c000139d eflags 0x00000002: id vip vif ac vm rf nt IOPL=0 of df if tf sf zf af pf cf segments context (before iret) Code: es:0x0023, dh=0x00cff300, dl=0x0000ffff, valid=1 Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed cs:0x0008, dh=0x00cf9b00, dl=0x0000ffff, valid=1 Code segment, base=0x00000000, limit=0xffffffff, Execute/Read, Accessed, 32-bit ss:0x0010, dh=0x00cf9300, dl=0x0000ffff, valid=7 Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed ds:0x0023, dh=0x00cff300, dl=0x0000ffff, valid=1 Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed fs:0x0023, dh=0x00cff300, dl=0x0000ffff, valid=1 Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed gs:0x0023, dh=0x00cff300, dl=0x0000ffff, valid=1 Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed ldtr:0x0000, dh=0x00008200, dl=0x0000ffff, valid=1 tr:0x002b, dh=0xc000eb00, dl=0x95d89640, valid=1 gdtr:base=0x00000000c0008d6e, limit=0x2f idtr:base=0x00000000c0008da4, limit=0x7ff Code: .show gdt Idx BaseHI BaseLO BaseMid Flags Grand Limit 0 0 0 0 0 0 0 1 0 0 0 9B CF FFFF 2 0 0 0 92 CF FFFF 3 0 0 0 FA CF FFFF 4 0 0 0 F2 CF FFFF 5 C0 95D8 0 EB 0 9640 .show idt index Enter the IDT index > 128 Idx BaseHI BaseLO Flag Reserved Sel 128 C000 2330 EE 0 8 any clue? _________________ _____________ Think it, build it, bit by bit... |
| Fri Nov 05, 2010 9:21 pm |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release Code: a) [0x001022bf] 0008:00000000c00022bf (unk. ctxt): push 0x0000001b ; 6a1b b) [0x001022c1] 0008:00000000c00022c1 (unk. ctxt): lea eax, dword ptr ds:0xc00022c9 ; 8d05c92200c0 c) [0x001022c7] 0008:00000000c00022c7 (unk. ctxt): push eax ; 50 d) [0x001022c8] 0008:00000000c00022c8 (unk. ctxt): iretd ; cf e) [0x001022c9] 001b:00000000c00022c9 (unk. ctxt): add esp, 0x00000004 ; 83c404 f) [0x00100690] 0008:00000000c0000690 (unk. ctxt): push ebp ; 55 ----------------------------------------------------CS:8 (error handler) I notice that it really goes to the user environment (as you can see at line e)... (CS gets 1B and EIP gets the effective address of label a) ... But, any instructions found there, invokes the page fault error _________________ _____________ Think it, build it, bit by bit... |
| Sat Nov 06, 2010 5:14 pm |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release I believe I found what I think is the problem.
Since the "_mmngr_used_blocks" and "_mmngr_max_blocks" is pointing to the same value, it never reaches the code that sets the pages flags property (I86_PTE_USER)! More, I thing that pmmngr_init should appear before vmmngr_initialize to set values to the variables used in vmmngr_initialize... That is the problem to the "user land" page fault... Lets remember that pages for the kernel remains mapped to "kernel mode-access only" (from loader) (or 3)... (cracking the system: I changed the Loader to ORing by 7d and all works perfect... but, of course isn't the correct solution, since the kernel should run on protected environment) let me knows, please.... _________________ _____________ Think it, build it, bit by bit... |
| Sun Nov 07, 2010 12:20 pm |
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Site Admin Joined: Sat Oct 20, 2007 7:58 pm Posts: 454
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Re: Chapter 23 Demo Release Hello,
Insightsoft wrote: More, I thing that pmmngr_init should appear before vmmngr_initialize to set values to the variables used in vmmngr_initialize... The above is related to the bug fix update mentioned earlier. The bug fix involves some additions to the vmmgr and the above (pmmngr_init should be first) that should resolve the portability issues. An easy way to apply the update is to copy an updated demo's vmmngr.cpp/h and paste it over this demos vmmngr.cpp/h and apply the above change moving the vmmngr_init call right after initializing the pmm. I do not believe there are additional changes that are needed for this patch. Quote: That is the problem to the "user land" page fault... Lets remember that pages for the kernel remains mapped to "kernel mode-access only" (from loader) (or 3) This is the usual case, yes. However this demo sets the I86_PTE_USER bit for kernel pages allowing user mode software this for simplicity. This allows the user mode software the capability of calling kernel functions in this demo without needing to go through system API. The vulnerability of the above is discussed in the chapter and can be rectified once a loader is in place (next chapter). This also means that, after applying the above patch, you will need to update vmmngr.cpp to set the I86_PTE_USER bits for the page directory and page tables. _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com |
| Sun Nov 07, 2010 4:51 pm |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release Thanks Mike,
I remember few months ago (maybe last year) , you was talking about making some changes to some demos to cover also Microsoft Virtual PC... Where can I get specification about, for example, Bochs and MSVPC?? (For me, when something runs in A and doesn't in B: I'm really in trouble!) About chapter 23. It runs in Bochs but doesn't run in MSVPC... I'm stuck! (I wish be able to fix this kind of problem) _________________ _____________ Think it, build it, bit by bit... |
| Thu Nov 11, 2010 5:23 am |
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Site Admin Joined: Sat Oct 20, 2007 7:58 pm Posts: 454
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Re: Chapter 23 Demo Release Hello,
Quote: Where can I get specification about, for example, Bochs and MSVPC? The source code of Bochs can be obtained online as well as documentation. VirtualPC, however, does not provide technical information (disregarding the processor fault code). This is do to VPC not being an emulator. Quote: About chapter 23. It runs in Bochs but doesn't run in MSVPC Please note that the demo provided has been tested in VPC and Bochs. If it fails in VPC, there are a couple of steps that can be taken to find the problem: -In goto_user(), comment out the int 0x80 call and test. If it works, the system API is probably at fault; -If it still fails, it might be crashing on entry to user mode. This can be a #PF or #GPF. The exception code provided by VPC will help in determining what the cause is. Quote: At the moment of TSS register... should not be sizeof(tss_entry)-1 instead of base+sizeof(tss_entry)? You are correct there-that looks like an error. The demo, and Chapter 22's demo are planned for the memory management update this weekend, so this error should be corrected by then. _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com |
| Thu Nov 11, 2010 9:29 pm |
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Joined: Sun Jul 11, 2010 1:12 pm Posts: 19
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Re: Chapter 23 Demo Release What about the Chapter 22 Demo Update?
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| Thu Nov 25, 2010 7:23 pm |
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Joined: Wed Jul 22, 2009 6:44 am Posts: 63
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Re: Chapter 23 Demo Release Hi...
Mike, ...the loader crash at: Code: mov ebx, 0 ; 0x0000 mov ebp, IMAGE_RMODE_BASE ; 0x3000 mov esi, ImageName ; File to load call LoadFile ; load our file | | ... .LOAD_IMAGE: ; load the cluster mov ax, WORD [cluster] ; cluster to read pop es ; bx:bp=es:bx pop bx call ClusterLBA xor cx, cx mov cl, BYTE [bpbSectorsPerCluster] call ReadSectors (crash here) | | call LBACHS ; convert starting sector to CHS mov ah, 0x02 ; BIOS read sector mov al, 0x01 ; read one sector mov ch, BYTE [absoluteTrack] ; track mov cl, BYTE [absoluteSector] ; sector mov dh, BYTE [absoluteHead] ; head mov dl, BYTE [bsDriveNumber] ; drive int 0x13 ; invoke BIOS-------------------------------------------------<b>(crash here)</b> Q: When? A: When the ECX > 103 (in LoadFile) Code: ... pop ecx inc ecx ... if ecx > 103 then, at "call ReadSectors", inside "int 0x13" it crash... Here is the registers values, before the int 13 Code: ah=02 service al=01 number of sectors to read ch=0a track or cylinder cl=05 sector id to read dh=01 head dl=00 a: ES:BX 0000:FE00 the result in bochs is: Code: 00022741396i[FDD ] controller reset in software 00022746580i[CPU0 ] BOUND_GdMa: fails bounds test 00022746582i[CPU0 ] BOUND_GdMa: fails bounds test 00022746584i[CPU0 ] BOUND_GdMa: fails bounds test 00022746586i[CPU0 ] BOUND_GdMa: fails bounds test 00022746588i[CPU0 ] BOUND_GdMa: fails bounds test 00022746590i[CPU0 ] BOUND_GdMa: fails bounds test 00022746592i[CPU0 ] BOUND_GdMa: fails bounds test keep running... It seams to me that the problem is our buffer (0000:FE00) _________________ _____________ Think it, build it, bit by bit... |
| Fri Nov 26, 2010 2:40 pm |
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