[OSy] Podezreni na bug v msimu u syscallu

[Jethro]

Dobre dopoledne,
kdyz nyni finisujeme s rozhranim systemovych volani, zacal se nam nas
system chovat zvlastne a myslime si, ze jde o chybu v msimu. Pri zavolani
syscallu se skoci do kernel modu a v nem by mel (alespon dle manualu,
strana 100) byt v epc ulozena adresa volani syscallu (ten neni v branch
delay slotu). Kdyz se ale o nekolik instrukci nize epc vycte, je na nem
adresa jina. Nize prikladame cast vypisu z msimu s trace=on
 0  00002270    addiu sp, sp, 0xffe8    # sp: 0x42fe0->0x42fc8
 0  00002274    addiu a0, 0, 0x1        # a0: 0xf->0x1
 0  00002278    addiu a1, 0, 0x5e       # 0x5e=94, a1: 0x2270->0x5e
 0  0000227C    sw    s0, 0x10(sp)      # 0x10=16
 0  00002280    addu  a2, 0, 0          # a2: 0x43000->0x0
 0  00002284    lw    s0, 0x28(sp)      # 0x28=40, s0: 0x4242->0x1020
 0  00002288    sw    ra, 0x14(sp)      # 0x14=20
 0  0000228C    jal   +0x428            # 0x428=1064, ra: 0x2270->0x2294
 0  00002290    addu  a3, 0, 0
 0  000010A0    addiu sp, sp, 0xfff8    # sp: 0x42fc8->0x42fc0
 0  000010A4    sw    ra, 0x4(sp)
 0  000010A8    syscall0x0

Raised exception: Syscall

 0  80000180    j     +0x225e           # 0x225e=8798, cp0_cause:
0x80000000->0x00000020
 0  80000184    nop
 0  80008978    lui   k0, 0xb000        # 0xb000=45056, k0:
0x1000ff13->0xb0000000
 0  8000897C    ori   k0, k0, 0x0004    # k0: 0xb0000000->0xb0000004
 0  80008980    lw    k1, (k0)
 0  80008984    sll   k0, k1, 0x0a      # 0xa=10, k0: 0xb0000004->0x0
 0  80008988    lui   k1, 0x8000        # 0x8000=32768, k1: 0x0->0x80000000
 0  8000898C    addu  k1, k1, k0
 0  80008990    addiu k0, 0, 0x400      # 0x400=1024, k0: 0x0->0x400
 0  80008994    addu  k1, k1, k0        # k1: 0x80000000->0x80000400
 0  80008998    mfc0  k0, epc           # k0: 0x400->0x108c

v k0 bychom ocekavali 0x10A8, ale je tam 0x108C. V priloze posilame i
binarku (to doufam nebude problem se sdilenim naseho kodu), kdyby nam nekdo
mel cas a chut pomoci, zdrojak toto zpusobujici je v nasem repozitari pod
commitem 190a474
Budeme radi za pomoc nebo aspon popostrceni spravnym smerem.
Tym BaPoSt
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