Hi Dave,
today I attempted to run 'x86info' on my system, and I was awarded by
a bit unexpected answer:
ppc:~/x# x86info -v
x86info v1.12b. Dave Jones 2001-2003
Feedback to <[email protected]>.
readEntry: Bad address
Found 1 CPUppc:~/x
After some tweaking around I found that I cannot read some pages from /dev/mem -
- I get -EFAULT on them. x86info run to the 0x86000 and 0x87000 pages, as it
scans 0x80000-0x8FFFF range for mptable.
After some thinking I believe that CONFIG_DEBUG_PAGEALLOC
is responsible for this problem. Should x86info (and other programs which
attempt to scan physical memory) cope with this inability to read /dev/mem, or
should be kernel fixed so /dev/mem really accesses physical memory and not kernel's
view of it? Or should I simple stop using CONFIG_DEBUG_PAGEALLOC?
Thanks,
Petr Vandrovec
P.S.: I'm surprised that we handle also incorrect 'from' in copy_to_user() without
oopses.
Test code + output on my system:
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
int main(void) {
int f = open("/dev/mem", O_RDONLY);
unsigned int offs;
for (offs = 0; offs < 0x1000000; offs += 4096) {
char buf[4096];
int rd;
lseek(f, offs, SEEK_SET);
rd = read(f, buf, 4096);
if (rd != 4096) {
printf("Reading at 0x%08X (%u) gives %d/%m\n", offs, offs, rd);
}
}
close(f);
return 0;
}
/*
Reading at 0x00086000 (548864) gives -1/Bad address
Reading at 0x00087000 (552960) gives -1/Bad address
Reading at 0x0042E000 (4382720) gives -1/Bad address
Reading at 0x0042F000 (4386816) gives -1/Bad address
Reading at 0x00444000 (4472832) gives -1/Bad address
Reading at 0x00446000 (4481024) gives -1/Bad address
Reading at 0x00447000 (4485120) gives -1/Bad address
Reading at 0x00448000 (4489216) gives -1/Bad address
Reading at 0x00449000 (4493312) gives -1/Bad address
Reading at 0x00454000 (4538368) gives -1/Bad address
Reading at 0x00455000 (4542464) gives -1/Bad address
Reading at 0x00458000 (4554752) gives -1/Bad address
Reading at 0x00459000 (4558848) gives -1/Bad address
Reading at 0x0045C000 (4571136) gives -1/Bad address
Reading at 0x0045D000 (4575232) gives -1/Bad address
Reading at 0x0045E000 (4579328) gives -1/Bad address
Reading at 0x0045F000 (4583424) gives -1/Bad address
Reading at 0x00460000 (4587520) gives -1/Bad address
Reading at 0x00461000 (4591616) gives -1/Bad address
Reading at 0x00462000 (4595712) gives -1/Bad address
Reading at 0x00463000 (4599808) gives -1/Bad address
Reading at 0x00464000 (4603904) gives -1/Bad address
Reading at 0x00465000 (4608000) gives -1/Bad address
Reading at 0x00468000 (4620288) gives -1/Bad address
Reading at 0x00469000 (4624384) gives -1/Bad address
Reading at 0x0046A000 (4628480) gives -1/Bad address
Reading at 0x0046B000 (4632576) gives -1/Bad address
Reading at 0x0046C000 (4636672) gives -1/Bad address
Reading at 0x0046D000 (4640768) gives -1/Bad address
Reading at 0x00472000 (4661248) gives -1/Bad address
Reading at 0x00473000 (4665344) gives -1/Bad address
Reading at 0x00478000 (4685824) gives -1/Bad address
Reading at 0x00479000 (4689920) gives -1/Bad address
Reading at 0x004D2000 (5054464) gives -1/Bad address
Reading at 0x004D3000 (5058560) gives -1/Bad address
Reading at 0x004D6000 (5070848) gives -1/Bad address
Reading at 0x004D7000 (5074944) gives -1/Bad address
Reading at 0x004E0000 (5111808) gives -1/Bad address
Reading at 0x004E1000 (5115904) gives -1/Bad address
Reading at 0x004E6000 (5136384) gives -1/Bad address
Reading at 0x004E7000 (5140480) gives -1/Bad address
Reading at 0x00506000 (5267456) gives -1/Bad address
Reading at 0x00507000 (5271552) gives -1/Bad address
Reading at 0x0050E000 (5300224) gives -1/Bad address
Reading at 0x0050F000 (5304320) gives -1/Bad address
Reading at 0x00514000 (5324800) gives -1/Bad address
Reading at 0x00515000 (5328896) gives -1/Bad address
Reading at 0x00516000 (5332992) gives -1/Bad address
Reading at 0x00517000 (5337088) gives -1/Bad address
Reading at 0x0051C000 (5357568) gives -1/Bad address
Reading at 0x0051D000 (5361664) gives -1/Bad address
Reading at 0x00534000 (5455872) gives -1/Bad address
Reading at 0x00535000 (5459968) gives -1/Bad address
Reading at 0x00536000 (5464064) gives -1/Bad address
Reading at 0x00537000 (5468160) gives -1/Bad address
Reading at 0x0053A000 (5480448) gives -1/Bad address
Reading at 0x0053B000 (5484544) gives -1/Bad address
Reading at 0x00542000 (5513216) gives -1/Bad address
Reading at 0x00543000 (5517312) gives -1/Bad address
Reading at 0x0054A000 (5545984) gives -1/Bad address
Reading at 0x0054B000 (5550080) gives -1/Bad address
Reading at 0x00552000 (5578752) gives -1/Bad address
Reading at 0x00553000 (5582848) gives -1/Bad address
Reading at 0x00558000 (5603328) gives -1/Bad address
Reading at 0x00559000 (5607424) gives -1/Bad address
Reading at 0x00560000 (5636096) gives -1/Bad address
Reading at 0x00561000 (5640192) gives -1/Bad address
Reading at 0x00566000 (5660672) gives -1/Bad address
Reading at 0x00567000 (5664768) gives -1/Bad address
Reading at 0x00568000 (5668864) gives -1/Bad address
Reading at 0x00569000 (5672960) gives -1/Bad address
Reading at 0x0056A000 (5677056) gives -1/Bad address
Reading at 0x0056B000 (5681152) gives -1/Bad address
Reading at 0x0056C000 (5685248) gives -1/Bad address
Reading at 0x0056D000 (5689344) gives -1/Bad address
Reading at 0x0056E000 (5693440) gives -1/Bad address
Reading at 0x0056F000 (5697536) gives -1/Bad address
Reading at 0x00570000 (5701632) gives -1/Bad address
Reading at 0x00571000 (5705728) gives -1/Bad address
Reading at 0x00572000 (5709824) gives -1/Bad address
Reading at 0x00573000 (5713920) gives -1/Bad address
Reading at 0x00576000 (5726208) gives -1/Bad address
Reading at 0x00577000 (5730304) gives -1/Bad address
Reading at 0x0057B000 (5746688) gives -1/Bad address
Reading at 0x0057E000 (5758976) gives -1/Bad address
Reading at 0x0057F000 (5763072) gives -1/Bad address
Reading at 0x00586000 (5791744) gives -1/Bad address
Reading at 0x00587000 (5795840) gives -1/Bad address
Reading at 0x00588000 (5799936) gives -1/Bad address
Reading at 0x00589000 (5804032) gives -1/Bad address
Reading at 0x0059A000 (5873664) gives -1/Bad address
Reading at 0x0059B000 (5877760) gives -1/Bad address
Reading at 0x005A8000 (5931008) gives -1/Bad address
Reading at 0x005A9000 (5935104) gives -1/Bad address
Reading at 0x005AA000 (5939200) gives -1/Bad address
Reading at 0x005AB000 (5943296) gives -1/Bad address
Reading at 0x005AE000 (5955584) gives -1/Bad address
Reading at 0x005AF000 (5959680) gives -1/Bad address
Reading at 0x005B4000 (5980160) gives -1/Bad address
Reading at 0x005B5000 (5984256) gives -1/Bad address
Reading at 0x005C2000 (6037504) gives -1/Bad address
Reading at 0x005C3000 (6041600) gives -1/Bad address
Reading at 0x005C6000 (6053888) gives -1/Bad address
Reading at 0x005C7000 (6057984) gives -1/Bad address
Reading at 0x005D0000 (6094848) gives -1/Bad address
Reading at 0x005D1000 (6098944) gives -1/Bad address
Reading at 0x005D2000 (6103040) gives -1/Bad address
Reading at 0x005D3000 (6107136) gives -1/Bad address
Reading at 0x005DC000 (6144000) gives -1/Bad address
Reading at 0x005DD000 (6148096) gives -1/Bad address
Reading at 0x005E0000 (6160384) gives -1/Bad address
Reading at 0x005E1000 (6164480) gives -1/Bad address
Reading at 0x005EA000 (6201344) gives -1/Bad address
Reading at 0x005EB000 (6205440) gives -1/Bad address
Reading at 0x005EC000 (6209536) gives -1/Bad address
Reading at 0x005ED000 (6213632) gives -1/Bad address
Reading at 0x005EE000 (6217728) gives -1/Bad address
Reading at 0x005EF000 (6221824) gives -1/Bad address
Reading at 0x005FE000 (6283264) gives -1/Bad address
Reading at 0x005FF000 (6287360) gives -1/Bad address
Reading at 0x00622000 (6430720) gives -1/Bad address
Reading at 0x00634000 (6504448) gives -1/Bad address
Reading at 0x00635000 (6508544) gives -1/Bad address
Reading at 0x00637000 (6516736) gives -1/Bad address
Reading at 0x00638000 (6520832) gives -1/Bad address
Reading at 0x00658000 (6651904) gives -1/Bad address
Reading at 0x00659000 (6656000) gives -1/Bad address
Reading at 0x0065A000 (6660096) gives -1/Bad address
Reading at 0x0065B000 (6664192) gives -1/Bad address
Reading at 0x0065C000 (6668288) gives -1/Bad address
Reading at 0x0065D000 (6672384) gives -1/Bad address
Reading at 0x0065E000 (6676480) gives -1/Bad address
Reading at 0x0065F000 (6680576) gives -1/Bad address
Reading at 0x00668000 (6717440) gives -1/Bad address
Reading at 0x00669000 (6721536) gives -1/Bad address
Reading at 0x0066A000 (6725632) gives -1/Bad address
Reading at 0x0066B000 (6729728) gives -1/Bad address
Reading at 0x0069C000 (6930432) gives -1/Bad address
Reading at 0x0069D000 (6934528) gives -1/Bad address
Reading at 0x0069E000 (6938624) gives -1/Bad address
Reading at 0x0069F000 (6942720) gives -1/Bad address
Reading at 0x006AA000 (6987776) gives -1/Bad address
Reading at 0x006AB000 (6991872) gives -1/Bad address
Reading at 0x006C0000 (7077888) gives -1/Bad address
Reading at 0x006C1000 (7081984) gives -1/Bad address
Reading at 0x006C4000 (7094272) gives -1/Bad address
Reading at 0x006C5000 (7098368) gives -1/Bad address
Reading at 0x006E6000 (7233536) gives -1/Bad address
Reading at 0x006E7000 (7237632) gives -1/Bad address
Reading at 0x006F0000 (7274496) gives -1/Bad address
Reading at 0x006F1000 (7278592) gives -1/Bad address
Reading at 0x00721000 (7475200) gives -1/Bad address
Reading at 0x00759000 (7704576) gives -1/Bad address
Reading at 0x0078C000 (7913472) gives -1/Bad address
Reading at 0x0078D000 (7917568) gives -1/Bad address
Reading at 0x0078E000 (7921664) gives -1/Bad address
Reading at 0x0078F000 (7925760) gives -1/Bad address
Reading at 0x0079A000 (7970816) gives -1/Bad address
Reading at 0x0079B000 (7974912) gives -1/Bad address
Reading at 0x007AA000 (8036352) gives -1/Bad address
Reading at 0x007B2000 (8069120) gives -1/Bad address
Reading at 0x007B3000 (8073216) gives -1/Bad address
Reading at 0x007BA000 (8101888) gives -1/Bad address
Reading at 0x007BB000 (8105984) gives -1/Bad address
Reading at 0x007BC000 (8110080) gives -1/Bad address
Reading at 0x007BD000 (8114176) gives -1/Bad address
Reading at 0x007BE000 (8118272) gives -1/Bad address
Reading at 0x007C8000 (8159232) gives -1/Bad address
Reading at 0x007C9000 (8163328) gives -1/Bad address
Reading at 0x007CA000 (8167424) gives -1/Bad address
Reading at 0x007CB000 (8171520) gives -1/Bad address
Reading at 0x007EC000 (8306688) gives -1/Bad address
Reading at 0x007ED000 (8310784) gives -1/Bad address
Reading at 0x00800000 (8388608) gives -1/Bad address
Reading at 0x00801000 (8392704) gives -1/Bad address
Reading at 0x00802000 (8396800) gives -1/Bad address
Reading at 0x00803000 (8400896) gives -1/Bad address
Reading at 0x00804000 (8404992) gives -1/Bad address
Reading at 0x00805000 (8409088) gives -1/Bad address
Reading at 0x00806000 (8413184) gives -1/Bad address
Reading at 0x00807000 (8417280) gives -1/Bad address
Reading at 0x00808000 (8421376) gives -1/Bad address
Reading at 0x00809000 (8425472) gives -1/Bad address
Reading at 0x0080A000 (8429568) gives -1/Bad address
Reading at 0x0080B000 (8433664) gives -1/Bad address
Reading at 0x0080C000 (8437760) gives -1/Bad address
Reading at 0x0080D000 (8441856) gives -1/Bad address
Reading at 0x0080E000 (8445952) gives -1/Bad address
Reading at 0x0080F000 (8450048) gives -1/Bad address
Reading at 0x00810000 (8454144) gives -1/Bad address
Reading at 0x00811000 (8458240) gives -1/Bad address
Reading at 0x00812000 (8462336) gives -1/Bad address
Reading at 0x00813000 (8466432) gives -1/Bad address
Reading at 0x00814000 (8470528) gives -1/Bad address
Reading at 0x00815000 (8474624) gives -1/Bad address
Reading at 0x00816000 (8478720) gives -1/Bad address
Reading at 0x00817000 (8482816) gives -1/Bad address
Reading at 0x00818000 (8486912) gives -1/Bad address
Reading at 0x00819000 (8491008) gives -1/Bad address
Reading at 0x0081A000 (8495104) gives -1/Bad address
Reading at 0x0081B000 (8499200) gives -1/Bad address
Reading at 0x0081C000 (8503296) gives -1/Bad address
Reading at 0x0081D000 (8507392) gives -1/Bad address
Reading at 0x0081E000 (8511488) gives -1/Bad address
Reading at 0x0081F000 (8515584) gives -1/Bad address
Reading at 0x00820000 (8519680) gives -1/Bad address
Reading at 0x00821000 (8523776) gives -1/Bad address
Reading at 0x00822000 (8527872) gives -1/Bad address
Reading at 0x00823000 (8531968) gives -1/Bad address
Reading at 0x00824000 (8536064) gives -1/Bad address
Reading at 0x00825000 (8540160) gives -1/Bad address
Reading at 0x00826000 (8544256) gives -1/Bad address
Reading at 0x00827000 (8548352) gives -1/Bad address
Reading at 0x00828000 (8552448) gives -1/Bad address
Reading at 0x00829000 (8556544) gives -1/Bad address
Reading at 0x0082A000 (8560640) gives -1/Bad address
Reading at 0x0082B000 (8564736) gives -1/Bad address
Reading at 0x0082C000 (8568832) gives -1/Bad address
Reading at 0x0082D000 (8572928) gives -1/Bad address
Reading at 0x0082E000 (8577024) gives -1/Bad address
Reading at 0x0082F000 (8581120) gives -1/Bad address
Reading at 0x00830000 (8585216) gives -1/Bad address
Reading at 0x00831000 (8589312) gives -1/Bad address
Reading at 0x00832000 (8593408) gives -1/Bad address
Reading at 0x00833000 (8597504) gives -1/Bad address
Reading at 0x00834000 (8601600) gives -1/Bad address
Reading at 0x00835000 (8605696) gives -1/Bad address
Reading at 0x00836000 (8609792) gives -1/Bad address
Reading at 0x00837000 (8613888) gives -1/Bad address
Reading at 0x00838000 (8617984) gives -1/Bad address
Reading at 0x00839000 (8622080) gives -1/Bad address
Reading at 0x0083A000 (8626176) gives -1/Bad address
Reading at 0x0083B000 (8630272) gives -1/Bad address
Reading at 0x0083C000 (8634368) gives -1/Bad address
Reading at 0x0083D000 (8638464) gives -1/Bad address
Reading at 0x0083E000 (8642560) gives -1/Bad address
Reading at 0x0083F000 (8646656) gives -1/Bad address
Reading at 0x00840000 (8650752) gives -1/Bad address
Reading at 0x00841000 (8654848) gives -1/Bad address
Reading at 0x00842000 (8658944) gives -1/Bad address
Reading at 0x00843000 (8663040) gives -1/Bad address
Reading at 0x00844000 (8667136) gives -1/Bad address
Reading at 0x00845000 (8671232) gives -1/Bad address
Reading at 0x00846000 (8675328) gives -1/Bad address
Reading at 0x00847000 (8679424) gives -1/Bad address
Reading at 0x00870000 (8847360) gives -1/Bad address
Reading at 0x00871000 (8851456) gives -1/Bad address
Reading at 0x00872000 (8855552) gives -1/Bad address
Reading at 0x00873000 (8859648) gives -1/Bad address
Reading at 0x00874000 (8863744) gives -1/Bad address
Reading at 0x00875000 (8867840) gives -1/Bad address
Reading at 0x00876000 (8871936) gives -1/Bad address
Reading at 0x00877000 (8876032) gives -1/Bad address
Reading at 0x00878000 (8880128) gives -1/Bad address
Reading at 0x00879000 (8884224) gives -1/Bad address
Reading at 0x0087A000 (8888320) gives -1/Bad address
Reading at 0x0087B000 (8892416) gives -1/Bad address
Reading at 0x0087C000 (8896512) gives -1/Bad address
Reading at 0x0087D000 (8900608) gives -1/Bad address
Reading at 0x0087E000 (8904704) gives -1/Bad address
Reading at 0x0087F000 (8908800) gives -1/Bad address
Reading at 0x00888000 (8945664) gives -1/Bad address
Reading at 0x00889000 (8949760) gives -1/Bad address
Reading at 0x0088A000 (8953856) gives -1/Bad address
Reading at 0x0088B000 (8957952) gives -1/Bad address
Reading at 0x0088C000 (8962048) gives -1/Bad address
Reading at 0x0088D000 (8966144) gives -1/Bad address
Reading at 0x0088E000 (8970240) gives -1/Bad address
Reading at 0x0088F000 (8974336) gives -1/Bad address
Reading at 0x00890000 (8978432) gives -1/Bad address
Reading at 0x00891000 (8982528) gives -1/Bad address
Reading at 0x00892000 (8986624) gives -1/Bad address
Reading at 0x00893000 (8990720) gives -1/Bad address
Reading at 0x00894000 (8994816) gives -1/Bad address
Reading at 0x00895000 (8998912) gives -1/Bad address
Reading at 0x00896000 (9003008) gives -1/Bad address
Reading at 0x00897000 (9007104) gives -1/Bad address
Reading at 0x00898000 (9011200) gives -1/Bad address
Reading at 0x00899000 (9015296) gives -1/Bad address
Reading at 0x0089A000 (9019392) gives -1/Bad address
Reading at 0x0089B000 (9023488) gives -1/Bad address
Reading at 0x0089C000 (9027584) gives -1/Bad address
Reading at 0x0089D000 (9031680) gives -1/Bad address
Reading at 0x0089E000 (9035776) gives -1/Bad address
Reading at 0x0089F000 (9039872) gives -1/Bad address
Reading at 0x008B0000 (9109504) gives -1/Bad address
Reading at 0x008C0000 (9175040) gives -1/Bad address
Reading at 0x008C1000 (9179136) gives -1/Bad address
Reading at 0x008C2000 (9183232) gives -1/Bad address
Reading at 0x008C3000 (9187328) gives -1/Bad address
Reading at 0x008C4000 (9191424) gives -1/Bad address
Reading at 0x008C5000 (9195520) gives -1/Bad address
Reading at 0x008C6000 (9199616) gives -1/Bad address
Reading at 0x008C7000 (9203712) gives -1/Bad address
Reading at 0x008C8000 (9207808) gives -1/Bad address
Reading at 0x008C9000 (9211904) gives -1/Bad address
Reading at 0x008CA000 (9216000) gives -1/Bad address
Reading at 0x008CB000 (9220096) gives -1/Bad address
Reading at 0x008CC000 (9224192) gives -1/Bad address
Reading at 0x008CD000 (9228288) gives -1/Bad address
Reading at 0x008CE000 (9232384) gives -1/Bad address
Reading at 0x008CF000 (9236480) gives -1/Bad address
Reading at 0x008E0000 (9306112) gives -1/Bad address
Reading at 0x008E1000 (9310208) gives -1/Bad address
Reading at 0x008E2000 (9314304) gives -1/Bad address
Reading at 0x008E3000 (9318400) gives -1/Bad address
Reading at 0x008E4000 (9322496) gives -1/Bad address
Reading at 0x008E5000 (9326592) gives -1/Bad address
Reading at 0x008E6000 (9330688) gives -1/Bad address
Reading at 0x008E7000 (9334784) gives -1/Bad address
Reading at 0x008E8000 (9338880) gives -1/Bad address
Reading at 0x008E9000 (9342976) gives -1/Bad address
Reading at 0x008EA000 (9347072) gives -1/Bad address
Reading at 0x008EB000 (9351168) gives -1/Bad address
Reading at 0x008EC000 (9355264) gives -1/Bad address
Reading at 0x008ED000 (9359360) gives -1/Bad address
Reading at 0x008EE000 (9363456) gives -1/Bad address
Reading at 0x008EF000 (9367552) gives -1/Bad address
Reading at 0x00900000 (9437184) gives -1/Bad address
Reading at 0x00901000 (9441280) gives -1/Bad address
Reading at 0x00902000 (9445376) gives -1/Bad address
Reading at 0x00903000 (9449472) gives -1/Bad address
Reading at 0x00904000 (9453568) gives -1/Bad address
Reading at 0x00905000 (9457664) gives -1/Bad address
Reading at 0x00906000 (9461760) gives -1/Bad address
Reading at 0x00907000 (9465856) gives -1/Bad address
Reading at 0x00908000 (9469952) gives -1/Bad address
Reading at 0x00909000 (9474048) gives -1/Bad address
Reading at 0x0090A000 (9478144) gives -1/Bad address
Reading at 0x0090B000 (9482240) gives -1/Bad address
Reading at 0x0090C000 (9486336) gives -1/Bad address
Reading at 0x0090D000 (9490432) gives -1/Bad address
Reading at 0x0090E000 (9494528) gives -1/Bad address
Reading at 0x0090F000 (9498624) gives -1/Bad address
Reading at 0x00910000 (9502720) gives -1/Bad address
Reading at 0x00911000 (9506816) gives -1/Bad address
Reading at 0x00912000 (9510912) gives -1/Bad address
Reading at 0x00913000 (9515008) gives -1/Bad address
Reading at 0x00914000 (9519104) gives -1/Bad address
Reading at 0x00915000 (9523200) gives -1/Bad address
Reading at 0x00916000 (9527296) gives -1/Bad address
Reading at 0x00917000 (9531392) gives -1/Bad address
Reading at 0x00918000 (9535488) gives -1/Bad address
Reading at 0x00919000 (9539584) gives -1/Bad address
Reading at 0x0091A000 (9543680) gives -1/Bad address
Reading at 0x0091B000 (9547776) gives -1/Bad address
Reading at 0x0091C000 (9551872) gives -1/Bad address
Reading at 0x0091D000 (9555968) gives -1/Bad address
Reading at 0x0091E000 (9560064) gives -1/Bad address
Reading at 0x0091F000 (9564160) gives -1/Bad address
Reading at 0x00920000 (9568256) gives -1/Bad address
Reading at 0x00921000 (9572352) gives -1/Bad address
Reading at 0x00922000 (9576448) gives -1/Bad address
Reading at 0x00923000 (9580544) gives -1/Bad address
Reading at 0x00924000 (9584640) gives -1/Bad address
Reading at 0x00925000 (9588736) gives -1/Bad address
Reading at 0x00926000 (9592832) gives -1/Bad address
Reading at 0x00927000 (9596928) gives -1/Bad address
Reading at 0x00928000 (9601024) gives -1/Bad address
Reading at 0x00929000 (9605120) gives -1/Bad address
Reading at 0x0092E000 (9625600) gives -1/Bad address
Reading at 0x0092F000 (9629696) gives -1/Bad address
Reading at 0x00940000 (9699328) gives -1/Bad address
Reading at 0x00941000 (9703424) gives -1/Bad address
Reading at 0x00942000 (9707520) gives -1/Bad address
Reading at 0x00943000 (9711616) gives -1/Bad address
Reading at 0x00944000 (9715712) gives -1/Bad address
Reading at 0x00945000 (9719808) gives -1/Bad address
Reading at 0x00946000 (9723904) gives -1/Bad address
Reading at 0x00947000 (9728000) gives -1/Bad address
Reading at 0x00950000 (9764864) gives -1/Bad address
Reading at 0x00951000 (9768960) gives -1/Bad address
Reading at 0x00952000 (9773056) gives -1/Bad address
Reading at 0x00953000 (9777152) gives -1/Bad address
Reading at 0x00954000 (9781248) gives -1/Bad address
Reading at 0x00955000 (9785344) gives -1/Bad address
Reading at 0x00956000 (9789440) gives -1/Bad address
Reading at 0x00957000 (9793536) gives -1/Bad address
Reading at 0x00958000 (9797632) gives -1/Bad address
Reading at 0x00959000 (9801728) gives -1/Bad address
Reading at 0x0095A000 (9805824) gives -1/Bad address
Reading at 0x0095B000 (9809920) gives -1/Bad address
Reading at 0x0095C000 (9814016) gives -1/Bad address
Reading at 0x0095D000 (9818112) gives -1/Bad address
Reading at 0x0095E000 (9822208) gives -1/Bad address
Reading at 0x0095F000 (9826304) gives -1/Bad address
Reading at 0x00970000 (9895936) gives -1/Bad address
Reading at 0x00971000 (9900032) gives -1/Bad address
Reading at 0x00972000 (9904128) gives -1/Bad address
Reading at 0x00973000 (9908224) gives -1/Bad address
Reading at 0x00974000 (9912320) gives -1/Bad address
Reading at 0x00975000 (9916416) gives -1/Bad address
Reading at 0x00976000 (9920512) gives -1/Bad address
Reading at 0x00977000 (9924608) gives -1/Bad address
Reading at 0x00978000 (9928704) gives -1/Bad address
Reading at 0x00979000 (9932800) gives -1/Bad address
Reading at 0x0097A000 (9936896) gives -1/Bad address
Reading at 0x0097B000 (9940992) gives -1/Bad address
Reading at 0x0097C000 (9945088) gives -1/Bad address
Reading at 0x0097D000 (9949184) gives -1/Bad address
Reading at 0x0097E000 (9953280) gives -1/Bad address
Reading at 0x0097F000 (9957376) gives -1/Bad address
Reading at 0x00988000 (9994240) gives -1/Bad address
Reading at 0x00989000 (9998336) gives -1/Bad address
Reading at 0x0098A000 (10002432) gives -1/Bad address
Reading at 0x0098B000 (10006528) gives -1/Bad address
Reading at 0x00990000 (10027008) gives -1/Bad address
Reading at 0x00991000 (10031104) gives -1/Bad address
Reading at 0x00992000 (10035200) gives -1/Bad address
Reading at 0x00993000 (10039296) gives -1/Bad address
Reading at 0x00994000 (10043392) gives -1/Bad address
Reading at 0x00995000 (10047488) gives -1/Bad address
Reading at 0x00996000 (10051584) gives -1/Bad address
Reading at 0x00997000 (10055680) gives -1/Bad address
Reading at 0x00998000 (10059776) gives -1/Bad address
Reading at 0x00999000 (10063872) gives -1/Bad address
Reading at 0x0099A000 (10067968) gives -1/Bad address
Reading at 0x0099B000 (10072064) gives -1/Bad address
Reading at 0x0099C000 (10076160) gives -1/Bad address
Reading at 0x0099D000 (10080256) gives -1/Bad address
Reading at 0x0099E000 (10084352) gives -1/Bad address
Reading at 0x0099F000 (10088448) gives -1/Bad address
Reading at 0x009B3000 (10170368) gives -1/Bad address
Reading at 0x009C3000 (10235904) gives -1/Bad address
Reading at 0x009F4000 (10436608) gives -1/Bad address
Reading at 0x009F5000 (10440704) gives -1/Bad address
Reading at 0x009FC000 (10469376) gives -1/Bad address
Reading at 0x009FD000 (10473472) gives -1/Bad address
Reading at 0x00A26000 (10641408) gives -1/Bad address
Reading at 0x00A44000 (10764288) gives -1/Bad address
Reading at 0x00A45000 (10768384) gives -1/Bad address
Reading at 0x00A46000 (10772480) gives -1/Bad address
Reading at 0x00A47000 (10776576) gives -1/Bad address
Reading at 0x00A78000 (10977280) gives -1/Bad address
Reading at 0x00A79000 (10981376) gives -1/Bad address
Reading at 0x00A7A000 (10985472) gives -1/Bad address
Reading at 0x00A7B000 (10989568) gives -1/Bad address
Reading at 0x00A95000 (11096064) gives -1/Bad address
Reading at 0x00A9C000 (11124736) gives -1/Bad address
Reading at 0x00A9D000 (11128832) gives -1/Bad address
Reading at 0x00A9E000 (11132928) gives -1/Bad address
Reading at 0x00A9F000 (11137024) gives -1/Bad address
Reading at 0x00AA0000 (11141120) gives -1/Bad address
Reading at 0x00AAD000 (11194368) gives -1/Bad address
Reading at 0x00AAF000 (11202560) gives -1/Bad address
Reading at 0x00AB5000 (11227136) gives -1/Bad address
Reading at 0x00ACC000 (11321344) gives -1/Bad address
Reading at 0x00ACD000 (11325440) gives -1/Bad address
Reading at 0x00ACE000 (11329536) gives -1/Bad address
Reading at 0x00ACF000 (11333632) gives -1/Bad address
Reading at 0x00AD0000 (11337728) gives -1/Bad address
Reading at 0x00AD1000 (11341824) gives -1/Bad address
Reading at 0x00AD2000 (11345920) gives -1/Bad address
Reading at 0x00AD3000 (11350016) gives -1/Bad address
Reading at 0x00AF0000 (11468800) gives -1/Bad address
Reading at 0x00AF1000 (11472896) gives -1/Bad address
Reading at 0x00AF2000 (11476992) gives -1/Bad address
Reading at 0x00AF3000 (11481088) gives -1/Bad address
Reading at 0x00B12000 (11608064) gives -1/Bad address
Reading at 0x00B9C000 (12173312) gives -1/Bad address
Reading at 0x00B9D000 (12177408) gives -1/Bad address
Reading at 0x00B9E000 (12181504) gives -1/Bad address
Reading at 0x00B9F000 (12185600) gives -1/Bad address
Reading at 0x00BC4000 (12337152) gives -1/Bad address
Reading at 0x00BC5000 (12341248) gives -1/Bad address
Reading at 0x00BC6000 (12345344) gives -1/Bad address
Reading at 0x00BC7000 (12349440) gives -1/Bad address
Reading at 0x00C22000 (12722176) gives -1/Bad address
Reading at 0x00C23000 (12726272) gives -1/Bad address
Reading at 0x00CB2000 (13312000) gives -1/Bad address
Reading at 0x00CB4000 (13320192) gives -1/Bad address
Reading at 0x00CB5000 (13324288) gives -1/Bad address
Reading at 0x00CB6000 (13328384) gives -1/Bad address
Reading at 0x00CB7000 (13332480) gives -1/Bad address
Reading at 0x00CBC000 (13352960) gives -1/Bad address
Reading at 0x00CBD000 (13357056) gives -1/Bad address
Reading at 0x00CBE000 (13361152) gives -1/Bad address
Reading at 0x00CBF000 (13365248) gives -1/Bad address
Reading at 0x00CC4000 (13385728) gives -1/Bad address
Reading at 0x00CC5000 (13389824) gives -1/Bad address
Reading at 0x00CC6000 (13393920) gives -1/Bad address
Reading at 0x00CC7000 (13398016) gives -1/Bad address
Reading at 0x00CF3000 (13578240) gives -1/Bad address
Reading at 0x00CF8000 (13598720) gives -1/Bad address
Reading at 0x00CF9000 (13602816) gives -1/Bad address
Reading at 0x00CFA000 (13606912) gives -1/Bad address
Reading at 0x00CFB000 (13611008) gives -1/Bad address
Reading at 0x00D04000 (13647872) gives -1/Bad address
Reading at 0x00D05000 (13651968) gives -1/Bad address
Reading at 0x00D06000 (13656064) gives -1/Bad address
Reading at 0x00D07000 (13660160) gives -1/Bad address
Reading at 0x00D13000 (13709312) gives -1/Bad address
Reading at 0x00D33000 (13840384) gives -1/Bad address
Reading at 0x00DB0000 (14352384) gives -1/Bad address
Reading at 0x00DB1000 (14356480) gives -1/Bad address
Reading at 0x00DB2000 (14360576) gives -1/Bad address
Reading at 0x00DB3000 (14364672) gives -1/Bad address
Reading at 0x00E30000 (14876672) gives -1/Bad address
Reading at 0x00E31000 (14880768) gives -1/Bad address
Reading at 0x00E32000 (14884864) gives -1/Bad address
Reading at 0x00E33000 (14888960) gives -1/Bad address
Reading at 0x00E44000 (14958592) gives -1/Bad address
Reading at 0x00E45000 (14962688) gives -1/Bad address
Reading at 0x00E4C000 (14991360) gives -1/Bad address
Reading at 0x00E58000 (15040512) gives -1/Bad address
Reading at 0x00E64000 (15089664) gives -1/Bad address
Reading at 0x00E65000 (15093760) gives -1/Bad address
Reading at 0x00E88000 (15237120) gives -1/Bad address
Reading at 0x00E89000 (15241216) gives -1/Bad address
Reading at 0x00E8A000 (15245312) gives -1/Bad address
Reading at 0x00E8B000 (15249408) gives -1/Bad address
Reading at 0x00EC8000 (15499264) gives -1/Bad address
Reading at 0x00EC9000 (15503360) gives -1/Bad address
Reading at 0x00EE4000 (15613952) gives -1/Bad address
Reading at 0x00EE5000 (15618048) gives -1/Bad address
Reading at 0x00F10000 (15794176) gives -1/Bad address
Reading at 0x00F11000 (15798272) gives -1/Bad address
Reading at 0x00F12000 (15802368) gives -1/Bad address
Reading at 0x00F13000 (15806464) gives -1/Bad address
Reading at 0x00F44000 (16007168) gives -1/Bad address
Reading at 0x00F45000 (16011264) gives -1/Bad address
Reading at 0x00F4C000 (16039936) gives -1/Bad address
Reading at 0x00F4D000 (16044032) gives -1/Bad address
Reading at 0x00F70000 (16187392) gives -1/Bad address
Reading at 0x00F71000 (16191488) gives -1/Bad address
Reading at 0x00F72000 (16195584) gives -1/Bad address
Reading at 0x00F73000 (16199680) gives -1/Bad address
Reading at 0x00FB6000 (16474112) gives -1/Bad address
Reading at 0x00FDE000 (16637952) gives -1/Bad address
Reading at 0x00FDF000 (16642048) gives -1/Bad address
Reading at 0x00FE8000 (16678912) gives -1/Bad address
Reading at 0x00FE9000 (16683008) gives -1/Bad address
Reading at 0x00FF5000 (16732160) gives -1/Bad address
*/
On Sat, 8 Nov 2003, Petr Vandrovec wrote:
> Hi Dave,
> today I attempted to run 'x86info' on my system, and I was awarded by
> a bit unexpected answer:
>
> ppc:~/x# x86info -v
> x86info v1.12b. Dave Jones 2001-2003
> Feedback to <[email protected]>.
>
> readEntry: Bad address
> Found 1 CPUppc:~/x
>
>
> After some tweaking around I found that I cannot read some pages from /dev/mem -
> - I get -EFAULT on them. x86info run to the 0x86000 and 0x87000 pages, as it
> scans 0x80000-0x8FFFF range for mptable.
>
Your code works on 2.4.22 and probably somewhat higher versions. However,
as I understand it, the new kernels no longer mmap everything by default.
In other words, there are no PTEs unless you or a driver sets them.
In user-mode, you need to mmap() and in kernel mode, you use ioremap_*().
Since you can mmap() something that is already mmapped() without any
problem, the code should probably be "fixed" to mmap everything it
tries to read, page-by-page.
If this is not correct, I'm sure somebody will respond.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.22 on an i686 machine (797.90 BogoMips).
Note 96.31% of all statistics are fiction.
On Sat, Nov 08, 2003 at 05:27:37PM +0100, Petr Vandrovec wrote:
> After some tweaking around I found that I cannot read some pages from /dev/mem -
> - I get -EFAULT on them. x86info run to the 0x86000 and 0x87000 pages, as it
> scans 0x80000-0x8FFFF range for mptable.
>
> After some thinking I believe that CONFIG_DEBUG_PAGEALLOC
> is responsible for this problem. Should x86info (and other programs which
> attempt to scan physical memory) cope with this inability to read /dev/mem, or
> should be kernel fixed so /dev/mem really accesses physical memory and not kernel's
> view of it? Or should I simple stop using CONFIG_DEBUG_PAGEALLOC?
I don't really have much insight into the behind the scenes going on's of
DEBUG_PAGEALLOC, so I don't know if your suggestion has merit or not.
Maybe Manfred can shed some insight? This does seem to be a regression IMO
(Though I am somewhat biased as this breaks my app 8-)
Dave
Dave Jones wrote:
>I don't really have much insight into the behind the scenes going on's of
>DEBUG_PAGEALLOC, so I don't know if your suggestion has merit or not.
>Maybe Manfred can shed some insight?
>
DEBUG_PAGEALLOC is not the only user of change_page_attr: gart also
removes it's pages from the linear mapping.
I think x86info should accept the -EFAULT as an indication that the
targeted page is in use for other purpose, and definitively doesn't
contain a mptable. The other option would be to change both
DEBUG_PAGEALLOC and the AGP gart driver
> This does seem to be a regression IMO
>(Though I am somewhat biased as this breaks my app 8-)
>
It breaks either your app or your AGP driver - what's simpler to fix?
I'm biased, because if you update the AGP driver, then I must figure out
how to fix DEBUG_PAGEALLOC 8-)
--
Manfred
On Mon, Nov 10, 2003 at 05:50:25PM +0100, Manfred Spraul wrote:
> It breaks either your app or your AGP driver - what's simpler to fix?
> I'm biased, because if you update the AGP driver, then I must figure out
> how to fix DEBUG_PAGEALLOC 8-)
I'm not convinced changing agpgart is worth the pain.
The only userspace app that actually grovels through the aperture
in this way is the agpgart test code, so this shouldn't be an issue.
I thought the DEBUG_PAGEALLOC stuff just unmapped pages that had been
kmalloc'd ? The area of memory we're trying to read those mptables from
shouldn't be unmapped in the first place should they ? Confused.
Dave
Dave Jones wrote:
>On Mon, Nov 10, 2003 at 05:50:25PM +0100, Manfred Spraul wrote:
> > It breaks either your app or your AGP driver - what's simpler to fix?
> > I'm biased, because if you update the AGP driver, then I must figure out
> > how to fix DEBUG_PAGEALLOC 8-)
>
>I'm not convinced changing agpgart is worth the pain.
>The only userspace app that actually grovels through the aperture
>in this way is the agpgart test code, so this shouldn't be an issue.
>
>
You misunderstood my objection:
we cannot assume that every page is mapped in the kernel linear mapping:
- with DEBUG_PAGEALLOC, lots of pages are removed from the linear mapping
- even without it, all pages that are used for AGP are removed from the
mapping.
Thus if something fails with DEBUG_PAGEALLOC, it will fail sometimes
with AGP gart as well.
>I thought the DEBUG_PAGEALLOC stuff just unmapped pages that had been
>kmalloc'd ? The area of memory we're trying to read those mptables from
>shouldn't be unmapped in the first place should they ? Confused.
>
>
DEBUG_PAGEALLOC unmaps pages on kmem_cache_free and __free_pages(). The
pages are mapped again during get_free_pages and kmem_cache_alloc.
0x86000 looks like a normal page - what guarantees that it's not used by
the kernel?
--
Manfred
On Mon, Nov 10, 2003 at 06:17:37PM +0100, Manfred Spraul wrote:
> DEBUG_PAGEALLOC unmaps pages on kmem_cache_free and __free_pages(). The
> pages are mapped again during get_free_pages and kmem_cache_alloc.
>
> 0x86000 looks like a normal page - what guarantees that it's not used by
> the kernel?
With DEBUG_PAGEALLOC there is no problem with page if it is USED by the kernel.
Problem is if page is NOT USED - in this case kernel does not have it in its
mapping, and bad thing happen.
x86info (and other simillar tools for dumping different BIOS structures) just
scans physical memory for some well known signatures - hoping that kernel did
not smash these structures.
Up to now it was possible to read whole physical memory from userspace - some
pages by reading /dev/mem, some pages by mmaping /dev/mem. Now it is not possible
anymore - which I think is bad, as /dev/mem has semantic of it. Manual (mem(4))
says that "mem is a character device file that is an image of the main memory
of the computer. It may be used, for example, to examine (and even patch) the
system." I have no idea what POSIX says about /dev/mem being unreadable...
Thanks anyway. As DEBUG_PAGEALLOC did not catch memory corruption I'm seeing,
I'll disable it.
Best regards,
Petr Vandrovec
Petr Vandrovec wrote:
>On Mon, Nov 10, 2003 at 06:17:37PM +0100, Manfred Spraul wrote:
>
>
>>DEBUG_PAGEALLOC unmaps pages on kmem_cache_free and __free_pages(). The
>>pages are mapped again during get_free_pages and kmem_cache_alloc.
>>
>>0x86000 looks like a normal page - what guarantees that it's not used by
>>the kernel?
>>
>>
>
>With DEBUG_PAGEALLOC there is no problem with page if it is USED by the kernel.
>Problem is if page is NOT USED - in this case kernel does not have it in its
>mapping, and bad thing happen.
>
>
If the page is used by AGP, then it won't have a mapping either.
>x86info (and other simillar tools for dumping different BIOS structures) just
>scans physical memory for some well known signatures - hoping that kernel did
>not smash these structures.
>
>
Scanning physical memory is very dangerous: it's undefined what happens
if a page is mapped multiple times with different cache settings. Athlon
cpus prefetch whatever they see, and they speculatively set the dirty
bit in cachelines for WB cacheable pages.
>Up to now it was possible to read whole physical memory from userspace - some
>pages by reading /dev/mem, some pages by mmaping /dev/mem. Now it is not possible
>anymore - which I think is bad, as /dev/mem has semantic of it.
>
I think /dev/mem should lie and return 0x00 for pages that are not in
the linear mapping.
Or /dev/mem users should expect random holes.
--
Manfred
Manfred Spraul wrote:
> Petr Vandrovec wrote:
>
>> On Mon, Nov 10, 2003 at 06:17:37PM +0100, Manfred Spraul wrote:
>>
>>
>>> DEBUG_PAGEALLOC unmaps pages on kmem_cache_free and __free_pages().
>>> The pages are mapped again during get_free_pages and kmem_cache_alloc.
>>>
>>> 0x86000 looks like a normal page - what guarantees that it's not
>>> used by the kernel?
>>>
>>
>>
>> With DEBUG_PAGEALLOC there is no problem with page if it is USED by
>> the kernel.
>> Problem is if page is NOT USED - in this case kernel does not have it
>> in its
>> mapping, and bad thing happen.
>>
>>
> If the page is used by AGP, then it won't have a mapping either.
>
afaics, agp uses change_apge_attr() to turn on NOCACHE bit, and doesn't
remove the mapping.
--Mika
Mika Penttil? wrote:
> afaics, agp uses change_apge_attr() to turn on NOCACHE bit, and
> doesn't remove the mapping.
Ops, you are right. Hmm. I'll add code to /dev/mem for DEBUG_PAGEALLOC,
but it might take some time.
--
Manfred
On Mon, Nov 10, 2003 at 08:47:54PM +0100, Manfred Spraul wrote:
> >afaics, agp uses change_apge_attr() to turn on NOCACHE bit, and
> >doesn't remove the mapping.
> Ops, you are right.
*grin*, I was beginning to think you knew something I didn't..
My cloud of confusion just drifted away 8-)
Dave