Styjun

What information about me do stores get via my credit card?

Ubuntu Server install with full GUI

What is this sharp, curved notch on my knife for?

How do I free up internal storage if I don't have any apps downloaded?

What does Linus Torvalds mean when he says that Git "never ever" tracks a file?

Can we generate random numbers using irrational numbers like π and e?

Why don't hard Brexiteers insist on a hard border to prevent illegal immigration after Brexit?

How to display lines in a file like ls displays files in a directory?

writing variables above the numbers in tikz picture

Why can't devices on different VLANs, but on the same subnet, communicate?

Inverse Relationship Between Precision and Recall

Can a flute soloist sit?

A word that means fill it to the required quantity

Did Scotland spend $250,000 for the slogan "Welcome to Scotland"?

How do PCB vias affect signal quality?

How to translate "being like"?

Why “相同意思的词” is called “同义词” instead of "同意词"？

Deal with toxic manager when you can't quit

Did the UK government pay "millions and millions of dollars" to try to snag Julian Assange?

How much of the clove should I use when using big garlic heads?

Relationship between Gromov-Witten and Taubes' Gromov invariant

What do these terms in Caesar's Gallic wars mean?

Is it safe to harvest rainwater that fell on solar panels?

Is it ethical to upload a automatically generated paper to a non peer-reviewed site as part of a larger research?

How to map physical memory safely in Linux?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;

0

I was following a tutorial about DMA, the goal is to move data fromm ddr to another part of ddr. In the example, it just mapped a 512MB physical memory using mmap and dev/mem, starting from some physical address like 0x20000000 and write data to it.

My question is that since we use virtual memory in linux, it is possible that other programs may already use some pages in this part of physical memory, how can we still writing these memory without damaging other programs accidentally?
Thanks.

Here's the part where physical memory is mapp:

 #define DDR_BASE_ADDRESS 0x20000000
 off_t dev_base_1 = DDR_BASE_ADDRESS;

 memfd_1 = open("/dev/mem", O_RDWR | O_SYNC);
 if (memfd_1 == -1)
 
 printf("Can't open /dev/mem.n");
 exit(0);
 
 printf("/dev/mem opened.n");
 mapped_base_1 = mmap(0, DDR_MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, memfd_1, dev_base_1 & ~DDR_MAP_MASK);

linux-kernel mmap

share|improve this question

asked Mar 22 at 4:33

j.youngj.young

164

add a comment | 

0

I was following a tutorial about DMA, the goal is to move data fromm ddr to another part of ddr. In the example, it just mapped a 512MB physical memory using mmap and dev/mem, starting from some physical address like 0x20000000 and write data to it.

My question is that since we use virtual memory in linux, it is possible that other programs may already use some pages in this part of physical memory, how can we still writing these memory without damaging other programs accidentally?
Thanks.

Here's the part where physical memory is mapp:

 #define DDR_BASE_ADDRESS 0x20000000
 off_t dev_base_1 = DDR_BASE_ADDRESS;

 memfd_1 = open("/dev/mem", O_RDWR | O_SYNC);
 if (memfd_1 == -1)
 
 printf("Can't open /dev/mem.n");
 exit(0);
 
 printf("/dev/mem opened.n");
 mapped_base_1 = mmap(0, DDR_MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, memfd_1, dev_base_1 & ~DDR_MAP_MASK);

linux-kernel mmap

share|improve this question

asked Mar 22 at 4:33

j.youngj.young

164

add a comment | 

I was following a tutorial about DMA, the goal is to move data fromm ddr to another part of ddr. In the example, it just mapped a 512MB physical memory using mmap and dev/mem, starting from some physical address like 0x20000000 and write data to it.

My question is that since we use virtual memory in linux, it is possible that other programs may already use some pages in this part of physical memory, how can we still writing these memory without damaging other programs accidentally?
Thanks.

Here's the part where physical memory is mapp:

 #define DDR_BASE_ADDRESS 0x20000000
 off_t dev_base_1 = DDR_BASE_ADDRESS;

 memfd_1 = open("/dev/mem", O_RDWR | O_SYNC);
 if (memfd_1 == -1)
 
 printf("Can't open /dev/mem.n");
 exit(0);
 
 printf("/dev/mem opened.n");
 mapped_base_1 = mmap(0, DDR_MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, memfd_1, dev_base_1 & ~DDR_MAP_MASK);

linux-kernel mmap

share|improve this question

asked Mar 22 at 4:33

j.youngj.young

164

 #define DDR_BASE_ADDRESS 0x20000000
 off_t dev_base_1 = DDR_BASE_ADDRESS;

 memfd_1 = open("/dev/mem", O_RDWR | O_SYNC);
 if (memfd_1 == -1)
 
 printf("Can't open /dev/mem.n");
 exit(0);
 
 printf("/dev/mem opened.n");
 mapped_base_1 = mmap(0, DDR_MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, memfd_1, dev_base_1 & ~DDR_MAP_MASK);

share|improve this question

asked Mar 22 at 4:33

j.youngj.young

164

share|improve this question

asked Mar 22 at 4:33

j.youngj.young

164

asked Mar 22 at 4:33

j.youngj.young

164

asked Mar 22 at 4:33

j.youngj.young

164