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Kernel: Implement read functionality for MemoryDevice

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So far we only had mmap(2) functionality on the /dev/mem device, but now
we can also do read(2) on it.

The test unit was updated to check we are doing it safely.
This commit is contained in:
Liav A 2021-12-23 21:49:31 +02:00 • committed by Idan Horowitz
parent 6feb07fe43
commit ca254699ec
4 changed files with 81 additions and 18 deletions
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76
Tests/Kernel/TestMemoryDeviceMmap.cpp
View file

@ -9,12 +9,16 @@
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
static u8 read_buffer[0x100000];
static ALWAYS_INLINE bool mem_chunk(int fd, u64 base, u64 length)
{
u64 mmoffset = base % sysconf(_SC_PAGESIZE);
@ -22,30 +26,80 @@ static ALWAYS_INLINE bool mem_chunk(int fd, u64 base, u64 length)
return mmp != MAP_FAILED;
}
enum class ReadResult {
SeekFailure,
ReadFailure,
ReadSuccess,
};
static ALWAYS_INLINE ReadResult read_chunk(int fd, u64 base, u64 length)
{
VERIFY(length <= sizeof(read_buffer));
auto rs = lseek(fd, base, SEEK_SET);
if (rs < 0) {
fprintf(stderr, "Couldn't seek to offset %" PRIi64 " while verifying: %s\n", base, strerror(errno));
return ReadResult::SeekFailure;
}
if (read(fd, read_buffer, length) < 0)
return ReadResult::ReadFailure;
return ReadResult::ReadSuccess;
}
TEST_CASE(test_memory_access_device_read)
{
int rc = geteuid();
EXPECT_EQ(rc, 0);
int fd = open("/dev/mem", O_RDONLY);
EXPECT(fd >= 0);
// FIXME: This is expected to work on QEMU machines (both 440FX and Q35),
// however, it will be much nicer to have some sort of a node in the ProcFS
// to expose physical memory ranges (e820 memory map).
auto read_result = read_chunk(fd, 0x0, 0x100000);
EXPECT_EQ(read_result, ReadResult::ReadFailure);
read_result = read_chunk(fd, 0xe0000, 0x100000 - 0xe0000);
EXPECT_EQ(read_result, ReadResult::ReadSuccess);
read_result = read_chunk(fd, 0x100000, 0x200000 - 0x100000);
EXPECT_EQ(read_result, ReadResult::ReadFailure);
read_result = read_chunk(fd, 0xf0000, 70000);
EXPECT_EQ(read_result, ReadResult::ReadFailure);
read_result = read_chunk(fd, 0xfffc0000, 16384);
EXPECT_EQ(read_result, ReadResult::ReadSuccess);
read_result = read_chunk(fd, 0xfffc0000, 0x100000);
EXPECT_EQ(read_result, ReadResult::ReadFailure);
}
TEST_CASE(test_memory_access_device_mmap)
{
int rc = geteuid();
EXPECT_EQ(rc, 0);
int fd = open("/dev/mem", O_RDONLY);
EXPECT_EQ(fd < 0, false);
EXPECT(fd >= 0);
// FIXME: This is expected to work on QEMU machines (both 440FX and Q35),
// however, it will be much nicer to have some sort of a node in the ProcFS
// to expose physical memory ranges (e820 memory map).
auto result = mem_chunk(fd, 0xe0000, 0x100000 - 0xe0000);
EXPECT_EQ(result, true);
auto mmap_result = mem_chunk(fd, 0xe0000, 0x100000 - 0xe0000);
EXPECT_EQ(mmap_result, true);
result = mem_chunk(fd, 0x100000, 0x200000 - 0x100000);
EXPECT_EQ(result, false);
mmap_result = mem_chunk(fd, 0x100000, 0x200000 - 0x100000);
EXPECT_EQ(mmap_result, false);
result = mem_chunk(fd, 0xf0000, 70000);
EXPECT_EQ(result, false);
mmap_result = mem_chunk(fd, 0xf0000, 70000);
EXPECT_EQ(mmap_result, false);
result = mem_chunk(fd, 0xfffc0000, 16384);
EXPECT_EQ(result, true);
mmap_result = mem_chunk(fd, 0xfffc0000, 16384);
EXPECT_EQ(mmap_result, true);
result = mem_chunk(fd, 0xfffc0000, 0x100000);
EXPECT_EQ(result, false);
mmap_result = mem_chunk(fd, 0xfffc0000, 0x100000);
EXPECT_EQ(mmap_result, false);
}