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Make font loading use mmap().

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This exposed a serious race condition in page_in_from_inode().
Reordered the logic and added a paging lock to VMObject.
Now, only one process can page in from a VMObject at a time.
There are definitely ways to optimize this, for instance by making
the locking be per-page instead. It's not something that I'm going
to worry about right now though.
This commit is contained in:
Andreas Kling 2019-02-03 01:36:25 +01:00
parent 7f91aec25c
commit abe3f515b1
4 changed files with 65 additions and 39 deletions
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49
SharedGraphics/Font.cpp
View file

@ -10,6 +10,7 @@
#include <LibC/stdio.h>
#include <LibC/fcntl.h>
#include <LibC/errno.h>
#include <LibC/mman.h>
#endif
#define DEFAULT_FONT_NAME Liza8x10
@ -101,43 +102,26 @@ struct FontFileHeader {
char name[64];
} PACKED;
RetainPtr<Font> Font::load_from_file(const String& path)
RetainPtr<Font> Font::load_from_memory(const byte* data)
{
int fd = open(path.characters(), O_RDONLY, 0644);
if (fd < 0) {
dbgprintf("open(%s) got fd=%d, failed: %s\n", path.characters(), fd, strerror(errno));
perror("open");
return nullptr;
}
FontFileHeader header;
ssize_t nread = read(fd, &header, sizeof(FontFileHeader));
if (nread != sizeof(FontFileHeader)) {
dbgprintf("nread != sizeof(FontFileHeader)=%u\n", sizeof(FontFileHeader));
return nullptr;
}
auto& header = *reinterpret_cast<const FontFileHeader*>(data);
if (memcmp(header.magic, "!Fnt", 4)) {
dbgprintf("header.magic != '!Fnt'\n");
dbgprintf("header.magic != '!Fnt', instead it's '%c%c%c%c'\n", header.magic[0], header.magic[1], header.magic[2], header.magic[3]);
return nullptr;
}
if (header.name[63] != '\0') {
dbgprintf("Font name not fully null-terminated\n");
return nullptr;
}
auto* glyphs_ptr = reinterpret_cast<const unsigned*>(data + sizeof(FontFileHeader));
char** new_glyphs = static_cast<char**>(kmalloc(sizeof(char*) * 256));
for (unsigned glyph_index = 0; glyph_index < 256; ++glyph_index) {
new_glyphs[glyph_index] = static_cast<char*>(kmalloc(header.glyph_width * header.glyph_height));
char* bitptr = new_glyphs[glyph_index];
for (unsigned y = 0; y < header.glyph_height; ++y) {
unsigned pattern;
ssize_t nread = read(fd, &pattern, sizeof(unsigned));
if (nread != sizeof(unsigned)) {
// FIXME: free() things and return nullptr.
ASSERT_NOT_REACHED();
}
unsigned pattern = *(glyphs_ptr++);
for (unsigned x = 0; x < header.glyph_width; ++x) {
if (pattern & (1u << x)) {
*(bitptr++) = '#';
@ -151,6 +135,25 @@ RetainPtr<Font> Font::load_from_file(const String& path)
return adopt(*new Font(String(header.name), new_glyphs, header.glyph_width, header.glyph_height, 0, 255));
}
RetainPtr<Font> Font::load_from_file(const String& path)
{
int fd = open(path.characters(), O_RDONLY, 0644);
if (fd < 0) {
dbgprintf("open(%s) got fd=%d, failed: %s\n", path.characters(), fd, strerror(errno));
perror("open");
return nullptr;
}
auto* mapped_file = (byte*)mmap(nullptr, 4096 * 3, PROT_READ, MAP_SHARED, fd, 0);
if (mapped_file == MAP_FAILED)
return nullptr;
auto font = load_from_memory(mapped_file);
int rc = munmap(mapped_file, 4096 * 3);
ASSERT(rc == 0);
return font;
}
bool Font::write_to_file(const String& path)
{
int fd = open(path.characters(), O_WRONLY | O_CREAT, 0644);