shoelace源代码分析，bochs调试-67870
在readkernel里面有调用0x67870处的一个call，而0x67870里面有一个jmp 9020:0000的跳转，
这正是我们要找的，并没有加载完运行startminix()函数，因为那是为启动minix要做的。
最后一个断点0x67870
b 0x6101f
c
s
最后在附上：readkernel的反汇编代码，里面为适应linux-0.11启动而改动的部分加红
<bochs:29> u /180
00060e7e: ( ): push bp ; 55
00060e7f: ( ): mov bp, sp ; 89e5
00060e81: ( ): push di ; 57
00060e82: ( ): push si ; 56
00060e83: ( ): add sp, 0xfffffffa ; 83c4fa
00060e86: ( ): mov al, byte ptr [ds:0x9f0c] ; a00c9f
00060e89: ( ): test al, al ; 84c0
00060e8b: ( ): jnz 0xe95 ; 7508
00060e8d: ( ): xor ax, ax ; 31c0
00060e8f: ( ): mov word ptr ss:[bp+0xfff6], ax ; 8946f6
00060e92: ( ): jmp 0xf42 ; e9ad00
00060e95: ( ): xor al, al ; 30c0
00060e97: ( ): mov byte ptr [ds:0x9f0c], al ; a20c9f
00060e9a: ( ): mov ax, 0x1f8 ; b8f801
00060e9d: ( ): mov word ptr ss:[bp+0xfffa], ax ; 8946fa
00060ea0: ( ): mov ax, 0x2 ; b80200
00060ea3: ( ): push ax ; 50
00060ea4: ( ): mov bx, 0x8506 ; bb0685
00060ea7: ( ): push bx ; 53
00060ea8: ( ): mov bx, word ptr ss:[bp+0x4] ; 8b5e04
00060eab: ( ): add bx, 0x1fe ; 81c3fe01
00060eaf: ( ): push bx ; 53
00060eb0: ( ): call 0x78ac ; e8f969
00060eb3: ( ): add sp, 0x6 ; 83c406
00060eb6: ( ): test ax, ax ; 85c0
00060eb8: ( ): jnz 0xec2 ; 7508
00060eba: ( ): mov ax, word ptr ss:[bp+0xfffa] ; 8b46fa
00060ebd: ( ): dec ax ; 48
00060ebe: ( ): dec ax ; 48
00060ebf: ( ): mov word ptr ss:[bp+0xfffa], ax ; 8946fa
00060ec2: ( ): mov ax, word ptr ss:[bp+0xfffa] ; 8b46fa
00060ec5: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00060ec8: ( ): mov bx, ax ; 89c3
00060eca: ( ): mov bx, word ptr ds:[bx] ; 8b1f
00060ecc: ( ): mov ax, bx ; 89d8
00060ece: ( ): inc ax ; 40
00060ecf: ( ): xor bx, bx ; 31db
00060ed1: ( ): push bx ; 53
00060ed2: ( ): push ax ; 50
00060ed3: ( ): mov ax, 0x200 ; b80002
00060ed6: ( ): xor bx, bx ; 31db
00060ed8: ( ): push bx ; 53
00060ed9: ( ): push ax ; 50
00060eda: ( ): mov ax, word ptr ss:[bp+0xfff2] ; 8b46f2
00060edd: ( ): mov bx, word ptr ss:[bp+0xfff4] ; 8b5ef4
00060ee0: ( ): lea di, word ptr ss:[bp+0xffee] ; 8d7eee
00060ee3: ( ): call 0x82bc ; e8d673
00060ee6: ( ): add sp, 0x8 ; 83c408
00060ee9: ( ): mov di, 0xaedc ; bfdcae
00060eec: ( ): call 0x8270 ; e88173
00060eef: ( ): jz 0xf0a ; 7419
00060ef1: ( ): mov ax, 0x1 ; b80100
00060ef4: ( ): mov [ds:0x8504], ax ; a30485
00060ef7: ( ): xor ax, ax ; 31c0
00060ef9: ( ): mov bx, 0x9 ; bb0900
00060efc: ( ): mov [ds:0x9f08], ax ; a3089f
00060eff: ( ): mov word ptr [ds:0x9f0a], bx ; 891e0a9f
00060f03: ( ): xor ax, ax ; 31c0
00060f05: ( ): mov word ptr ss:[bp+0xfff6], ax ; 8946f6
00060f08: ( ): jmp 0xf42 ; eb38
00060f0a: ( ): mov ax, word ptr ss:[bp+0xfffa] ; 8b46fa
00060f0d: ( ): inc ax ; 40
00060f0e: ( ): inc ax ; 40
00060f0f: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00060f12: ( ): mov bx, ax ; 89c3
00060f14: ( ): mov bx, word ptr ds:[bx] ; 8b1f
00060f16: ( ): mov word ptr [ds:0xae98], bx ; 891e98ae
00060f1a: ( ): mov ax, word ptr ss:[bp+0xfffa] ; 8b46fa
00060f1d: ( ): add ax, 0x4 ; 050400
00060f20: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00060f23: ( ): mov bx, ax ; 89c3
00060f25: ( ): mov bx, word ptr ds:[bx] ; 8b1f
00060f27: ( ): mov word ptr [ds:0xae94], bx ; 891e94ae
00060f2b: ( ): mov ax, word ptr ss:[bp+0xfffa] ; 8b46fa
00060f2e: ( ): add ax, 0x6 ; 050600
00060f31: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00060f34: ( ): mov bx, ax ; 89c3
00060f36: ( ): mov bx, word ptr ds:[bx] ; 8b1f
00060f38: ( ): mov word ptr [ds:0xae9c], bx ; 891e9cae
00060f3c: ( ): mov ax, 0x200 ; b80002
00060f3f: ( ): mov word ptr ss:[bp+0xfff6], ax ; 8946f6
00060f42: ( ): mov ax, 0x400 ; b80004
00060f45: ( ): sub ax, word ptr ss:[bp+0xfff6] ; 2b46f6
00060f48: ( ): mov word ptr ss:[bp+0xfff8], ax ; 8946f8
00060f4b: ( ): mov ax, word ptr ss:[bp+0xfff8] ; 8b46f8
00060f4e: ( ): xor bx, bx ; 31db
00060f50: ( ): mov di, 0xaedc ; bfdcae
00060f53: ( ): call 0x8270 ; e81a73
00060f56: ( ): jb 0xf5b ; 7203
00060f58: ( ): jmp 0xff3 ; e99800
00060f5b: ( ): push word ptr ss:[bp+0xfff8] ; ff76f8
00060f5e: ( ): push word ptr [ds:0x9f0a] ; ff360a9f
00060f62: ( ): push word ptr [ds:0x9f08] ; ff36089f
00060f66: ( ): mov ax, word ptr ss:[bp+0xfff6] ; 8b46f6
00060f69: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00060f6c: ( ): push ax ; 50
00060f6d: ( ): call 0xea ; e87af1
00060f70: ( ): add sp, 0x8 ; 83c408
00060f73: ( ): mov ax, word ptr ss:[bp+0xfff8] ; 8b46f8
00060f76: ( ): xor bx, bx ; 31db
00060f78: ( ): push bx ; 53
00060f79: ( ): push ax ; 50
00060f7a: ( ): mov ax, [ds:0xaedc] ; a1dcae
00060f7d: ( ): mov bx, word ptr [ds:0xaede] ; 8b1edeae
00060f81: ( ): lea di, word ptr ss:[bp+0xfff2] ; 8d7ef2
00060f84: ( ): call 0x8328 ; e8a173
00060f87: ( ): mov [ds:0xaedc], ax ; a3dcae
00060f8a: ( ): mov word ptr [ds:0xaede], bx ; 891edeae
00060f8e: ( ): add sp, 0x4 ; 83c404
00060f91: ( ): mov ax, word ptr ss:[bp+0xfff8] ; 8b46f8
00060f94: ( ): xor bx, bx ; 31db
00060f96: ( ): mov di, 0x9f08 ; bf089f
00060f99: ( ): call 0x8260 ; e8c472
00060f9c: ( ): mov [ds:0x9f08], ax ; a3089f
00060f9f: ( ): mov word ptr [ds:0x9f0a], bx ; 891e0a9f
00060fa3: ( ): mov ax, [ds:0x8504] ; a10485
00060fa6: ( ): test ax, ax ; 85c0
00060fa8: ( ): jz 0xfea ; 7440
00060faa: ( ): mov ax, 0xc00 ; b8000c
00060fad: ( ): mov bx, 0x9 ; bb0900
00060fb0: ( ): push bx ; 53
00060fb1: ( ): push ax ; 50
00060fb2: ( ): mov ax, [ds:0x9f08] ; a1089f
00060fb5: ( ): mov bx, word ptr [ds:0x9f0a] ; 8b1e0a9f
00060fb9: ( ): lea di, word ptr ss:[bp+0xfff2] ; 8d7ef2
00060fbc: ( ): call 0x8270 ; e8b172
00060fbf: ( ): lea sp, word ptr ss:[bp+0xfff6] ; 8d66f6
00060fc2: ( ): jnz 0xfea ; 7526
00060fc4: ( ): mov ax, 0x200 ; b80002
00060fc7: ( ): push ax ; 50
00060fc8: ( ): xor ax, ax ; 31c0
00060fca: ( ): mov bx, 0x1 ; bb0100
00060fcd: ( ): push bx ; 53
00060fce: ( ): push ax ; 50
00060fcf: ( ): mov bx, word ptr ss:[bp+0x4] ; 8b5e04
00060fd2: ( ): add bx, 0x200 ; 81c30002
00060fd6: ( ): push bx ; 53
00060fd7: ( ): call 0xea ; e810f1
00060fda: ( ): add sp, 0x8 ; 83c408
00060fdd: ( ): mov ax, 0x200 ; b80002
00060fe0: ( ): mov bx, 0x1 ; bb0100
00060fe3: ( ): mov [ds:0x9f08], ax ; a3089f
00060fe6: ( ): mov word ptr [ds:0x9f0a], bx ; 891e0a9f
00060fea: ( ): xor ax, ax ; 31c0
00060fec: ( ): add sp, 0x6 ; 83c406
00060fef: ( ): pop si ; 5e
00060ff0: ( ): pop di ; 5f
00060ff1: ( ): pop bp ; 5d
00060ff2: ( ): retn ; c3
00060ff3: ( ): push word ptr [ds:0xaedc] ; ff36dcae
00060ff7: ( ): push word ptr [ds:0x9f0a] ; ff360a9f
00060ffb: ( ): push word ptr [ds:0x9f08] ; ff36089f
00060fff: ( ): mov ax, word ptr ss:[bp+0xfff6] ; 8b46f6
00061002: ( ): add ax, word ptr ss:[bp+0x4] ; 034604
00061005: ( ): push ax ; 50
00061006: ( ): call 0xea ; e8e1f0
00061009: ( ): add sp, 0x8 ; 83c408
0006100c: ( ): mov ax, 0x1 ; b80100
0006100f: ( ): xor bx, bx ; 31db
00061011: ( ): mov [ds:0xaedc], ax ; a3dcae
00061014: ( ): mov word ptr [ds:0xaede], bx ; 891edeae
00061018: ( ): mov ax, [ds:0x8504] ; a10485
0006101b: ( ): test ax, ax ; 85c0
0006101d: ( ): jz 0x1022 ; 7403
0006101f: ( ): call 0x7870 ; e84e68
00061022: ( ): mov ax, 0x1 ; b80100
00061025: ( ): add sp, 0x6 ; 83c406
00061028: ( ): pop si ; 5e
00061029: ( ): pop di ; 5f
0006102a: ( ): pop bp ; 5d
0006102b: ( ): retn ; c3
在没有源码的情况下，猜测是正确的，
今天看到了shoelace.cdif文件的关键的修正部分：
X+ #define SETUPSEG 0x9020
X+ extern void startlinux();
X+ unsigned getdev();
X+
X static inode_nr
X readkernel F1(buffer *, bp)
X
X***************
X*** 627,641 ****
X
X if ( (long) (* (unsigned int *) (&((char *) bp)[build_base]) + 1)
X * SECTOR_SIZE != filesize) {
X! printf("%s conflicting size information\n", filename);
X! longjmp(errjmp, 1);
X! }
X!
X! fsck_ds = * (unsigned int *) (&((char *) bp)[build_base+2]);
X! fsck_pc = * (unsigned int *) (&((char *) bp)[build_base+4]);
X! fsck_cs = * (unsigned int *) (&((char *) bp)[build_base+6]);
X!
X! bpinx = SECTOR_SIZE;
X }
X
X bpsize = sizeof(*bp) - bpinx;
X--- 634,667 ----
X
X if ( (long) (* (unsigned int *) (&((char *) bp)[build_base]) + 1)
X * SECTOR_SIZE != filesize) {
X! /* printf("%s conflicting size information\n", filename);
X! longjmp(errjmp, 1);*/
X! unsigned *myptr = (unsigned int *) (&((char *) bp)[508]);
X! /*char *myroot = getenvs(SaveConfigPtr,"rootdev");
X! if (strcmp(myroot,"bootdev"))
X! *myptr = atoi(myroot);
X! else
X! *myptr = 0;
X! if (*myptr == 0)
X! { if (diskcode)
X! *myptr = DEV_HD0 + bootpart;
X! else
X! if (n_sectors = 15)
X! *myptr = 0x208;
X! else
X! *myptr = 0x21c;
X! }*/
X! Linux = 1;
X! LoadPoint = 0x90000;
X! bpinx = 0;
X! }
X! else {
X! fsck_ds = * (unsigned int *) (&((char *) bp)[build_base+2]);
X! fsck_pc = * (unsigned int *) (&((char *) bp)[build_base+4]);
X! fsck_cs = * (unsigned int *) (&((char *) bp)[build_base+6]);
X! bpinx = SECTOR_SIZE;
X! }
X!
X }
X
X bpsize = sizeof(*bp) - bpinx;
X***************
X*** 644,654 ****
X--- 670,687 ----
X copyto((char *) bp + bpinx, LoadPoint, bpsize);
X filesize -= bpsize;
X LoadPoint += bpsize;
X+ if (Linux && (LoadPoint==0x90C00))
X+ {
X+ copyto((char *) bp + SECTOR_SIZE, (ADDRESS)0x10000, SECTOR_SIZE);
X+ LoadPoint = 0x10200;
X+ }
X return 0;
X }
X
X copyto((char *) bp + bpinx, LoadPoint, (unsigned int) filesize);
X filesize = 1;
X+ if (Linux)
X+ startlinux();
X return ROOT_INODE;
X }
X.text
X.define _startlinux
X.text
X
XSETUPLEN = 4 | nr of setup-sectors
XBOOTSEG = 0x07c0 | original address of boot-sector
XINITSEG = 0x9000 | we move boot here - out of the way
XSETUPSEG = 0x9020 | setup starts here
XSYSSEG = 0x1000 | system loaded at 0x10000 (65536).
X
X| ROOT_DEV: 0x000 - same type of floppy as boot.
X| 0x301 - first partition on first drive etc
XROOT_DEV = 0x302 | 0x306
X
X_startlinux:
X mov ax,#BOOTSEG
X mov ds,ax
X mov ax,#INITSEG
X mov es,ax
Xgo: mov ax,cs
X mov ds,ax
X mov es,ax
X| put stack at 0x9ff00.
X mov ss,ax
X mov sp,#0xFF00 | arbitrary value >>512
X
Xok_load_setup:
X
X| Get disk drive parameters, specifically nr of sectors/track
X
X mov ch,#0x00
X seg cs
X| mov sectors,cx
X mov ax,#INITSEG
X mov es,ax
X
X
X
X seg cs
X
X| after that (everyting loaded), we jump to
X| the setup-routine loaded directly after
X| the bootblock:
X
X jmpi 0,SETUPSEG
X
X
X