Skip to content

tools: PAGE_SIZE mmap fallback for CONFIG_IO_STRICT_DEVMEM kernels #172

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
widgetii merged 1 commit into from
Jun 4, 2026
Merged

tools: PAGE_SIZE mmap fallback for CONFIG_IO_STRICT_DEVMEM kernels #172

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
39 changes: 24 additions & 15 deletions src/tools.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -41,18 +41,20 @@ bool mem_reg(uint32_t addr, uint32_t *data, enum REG_OPS op) {
return true;
}

uint32_t offset = addr & 0xffff0000;
uint32_t size = 0xffff;
if (!addr || (loaded_area && offset != loaded_offset)) {
bool in_cache = loaded_area && addr >= loaded_offset &&
addr - loaded_offset < loaded_size;
if (!addr || (loaded_area && !in_cache)) {
int res = munmap(loaded_area, loaded_size);
if (res) {
fprintf(stderr, "read_mem_reg error: %s (%d)\n", strerror(errno),
errno);
}
loaded_area = NULL;
}

if (!addr) {
close(mem_fd);
mem_fd = 0;
return true;
}

Expand All @@ -65,16 +67,23 @@ bool mem_reg(uint32_t addr, uint32_t *data, enum REG_OPS op) {
}

volatile char *mapped_area;
if (offset != loaded_offset) {
mapped_area =
mmap(NULL, // Any adddress in our space will do
size, // Map length
PROT_READ |
PROT_WRITE, // Enable reading & writting to mapped memory
MAP_SHARED, // Shared with other processes
mem_fd, // File to map
offset // Offset to base address
);
if (!loaded_area) {
uint32_t offset = addr & 0xffff0000;
uint32_t size = 0xffff;
mapped_area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
if (mapped_area == MAP_FAILED && errno == EPERM) {
// CONFIG_IO_STRICT_DEVMEM blocks any /dev/mem mmap whose range
// overlaps a driver-claimed page. Retry with a single page so
// the read at least succeeds when our target page itself isn't
// claimed (the 64 KiB window may have caught an unrelated
// sibling). See OpenIPC firmware PR for the kernel-side fix.
uint32_t page = (uint32_t)sysconf(_SC_PAGESIZE);
offset = addr & ~(page - 1);
size = page;
mapped_area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
}
if (mapped_area == MAP_FAILED) {
fprintf(stderr, "read_mem_reg mmap error: %s (%d)\n",
strerror(errno), errno);
Expand All @@ -87,9 +96,9 @@ bool mem_reg(uint32_t addr, uint32_t *data, enum REG_OPS op) {
mapped_area = loaded_area;

if (op == OP_READ)
*data = *(volatile uint32_t *)(mapped_area + (addr - offset));
*data = *(volatile uint32_t *)(mapped_area + (addr - loaded_offset));
else if (op == OP_WRITE)
*(volatile uint32_t *)(mapped_area + (addr - offset)) = *data;
*(volatile uint32_t *)(mapped_area + (addr - loaded_offset)) = *data;

return true;
}
Expand Down
Loading