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Smbios (FreeBSD): unifies pread/mmap handling

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Don't try `pread(/dev/mem)` on FreeBSD, which causes kernel panic
This commit is contained in:
Carter Li
2026-04-14 16:04:20 +08:00
parent 08de5eabed
commit 683e90cec6
1 changed files with 55 additions and 40 deletions
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src/common/impl/smbios.c
+55 -40
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@@ -1,6 +1,5 @@
#include "common/smbios.h"
#include "common/io.h"
#include "common/unused.h"
#include "common/mallocHelper.h"
#include "common/debug.h"
@@ -138,14 +137,54 @@ static bool parseSmbiosTable(const uint8_t* data, uint32_t length) {
# include "common/properties.h"
# elif defined(__FreeBSD__)
# include "common/settings.h"
# define loff_t off_t // FreeBSD doesn't have loff_t
# elif defined(__sun)
# define loff_t off_t
# elif defined(__sun) || defined(__OpenBSD__)
# define loff_t off_t
# elif defined(__NetBSD__)
# include "common/sysctl.h"
# define loff_t off_t
# endif
static bool readPhysicalMemory(int fd, loff_t address, size_t length, void* buffer) {
# if !defined(__FreeBSD__) // Either causes kernel panic or returns EFAULT
// -1: unknown, 0: failed before (stop trying), 1: succeeded before
static int preadState = -1;
if (preadState != 0) {
ssize_t bytesRead = pread(fd, buffer, length, address);
if (bytesRead == (ssize_t) length) {
preadState = 1;
return true;
}
FF_DEBUG("pread failed at address 0x%lx for %zu bytes: %s. Falling back to mmap%s",
(unsigned long) address,
length,
strerror(errno),
preadState < 0 ? " and caching failure" : "");
preadState = 0;
} else {
FF_DEBUG("Skipping pread due to cached failure; using mmap");
}
# endif
loff_t alignedAddress = address & ~((loff_t) instance.state.platform.sysinfo.pageSize - 1);
size_t pageOffset = (size_t) (address - alignedAddress);
size_t mapLength = pageOffset + length;
void* p = mmap(NULL, mapLength, PROT_READ, MAP_SHARED, fd, alignedAddress);
if (p == MAP_FAILED) {
FF_DEBUG("mmap failed at aligned address 0x%lx for %zu bytes: %s",
(unsigned long) alignedAddress,
mapLength,
strerror(errno));
return false;
}
memcpy(buffer, (const uint8_t*) p + pageOffset, length);
munmap(p, mapLength);
return true;
}
# ifdef __linux__
bool ffGetSmbiosValue(const char* devicesPath, const char* classPath, FFstrbuf* buffer) {
// /sys/class/dmi/id/* are all pseudo-files with very small content
@@ -291,22 +330,10 @@ const FFSmbiosHeaderTable* ffGetSmbiosHeaderTable() {
FF_DEBUG("Attempting to read %zu bytes from physical address 0x%lx",
sizeof(entryPoint),
(unsigned long) entryAddress);
if (pread(fd, &entryPoint, sizeof(entryPoint), entryAddress) < 0x10) {
FF_DEBUG("pread failed: %s. Trying mmap", strerror(errno));
// `pread /dev/mem` returns EFAULT in FreeBSD
// https://stackoverflow.com/questions/69372330/how-to-read-dev-mem-using-read
void* p = mmap(NULL, sizeof(entryPoint), PROT_READ, MAP_SHARED, fd, entryAddress);
if (p == MAP_FAILED) {
FF_DEBUG("mmap failed: %s", strerror(errno));
return NULL;
}
memcpy(&entryPoint, p, sizeof(entryPoint));
munmap(p, sizeof(entryPoint));
FF_DEBUG("Successfully read entry point data via mmap");
} else {
FF_DEBUG("Successfully read entry point data via pread");
if (!readPhysicalMemory(fd, entryAddress, sizeof(entryPoint), &entryPoint)) {
return NULL;
}
FF_DEBUG("Successfully read SMBIOS entry point data");
# else
// Sun or NetBSD
FF_DEBUG("Using %s specific implementation",
@@ -388,37 +415,25 @@ const FFSmbiosHeaderTable* ffGetSmbiosHeaderTable() {
ffStrbufEnsureFixedLengthFree(&buffer, tableLength);
FF_DEBUG("Attempting to read SMBIOS table data: %u bytes at 0x%lx", tableLength, (unsigned long) tableAddress);
if (pread(fd, buffer.chars, tableLength, tableAddress) == (ssize_t) tableLength) {
if (readPhysicalMemory(fd, tableAddress, tableLength, buffer.chars)) {
buffer.length = tableLength;
buffer.chars[buffer.length] = '\0';
FF_DEBUG("Successfully read SMBIOS table data: %u bytes", tableLength);
} else {
FF_DEBUG("pread failed, trying mmap");
// entryPoint.StructureTableAddress must be page aligned.
// Unaligned physical memory access results in all kinds of crashes.
void* p = mmap(NULL, tableLength, PROT_READ, MAP_SHARED, fd, tableAddress);
if (p == MAP_FAILED) {
FF_DEBUG("mmap failed: %s", strerror(errno));
ffStrbufDestroy(&buffer); // free buffer and reset state
return NULL;
}
ffStrbufSetNS(&buffer, tableLength, (char*) p);
munmap(p, tableLength);
FF_DEBUG("Successfully read SMBIOS table data via mmap: %u bytes", tableLength);
ffStrbufDestroy(&buffer); // free buffer and reset state
return NULL;
}
}
return NULL;
# endif
fallback:
if (buffer.length == 0) {
const char* devMem =
# if __HAIKU__
# if __HAIKU__
"/dev/misc/mem";
# else
# else
"/dev/mem"; // kern.securelevel must be -1
# endif
# endif
FF_DEBUG("Using physical memory searching implementation: %s", devMem);
uint32_t tableLength = 0;
@@ -436,8 +451,8 @@ const FFSmbiosHeaderTable* ffGetSmbiosHeaderTable() {
// However, to acquire SMBIOS entry point, we need EFI configuration table (provided by EFI system table)
// which is not available via EFIIOC_GET_TABLE.
FF_AUTO_FREE uint8_t* smBiosBase = malloc(0x10000);
if (pread(fd, smBiosBase, 0x10000, 0xF0000) != 0x10000) {
FF_DEBUG("Failed to read SMBIOS memory region: %s", strerror(errno));
if (!readPhysicalMemory(fd, 0xF0000, 0x10000, smBiosBase)) {
FF_DEBUG("Failed to read SMBIOS memory region");
return NULL;
}
FF_DEBUG("Successfully read 0x10000 bytes from physical address 0xF0000");
@@ -486,12 +501,12 @@ const FFSmbiosHeaderTable* ffGetSmbiosHeaderTable() {
ffStrbufEnsureFixedLengthFree(&buffer, tableLength);
FF_DEBUG("Attempting to read SMBIOS table data: %u bytes at 0x%lx", tableLength, (unsigned long) tableAddress);
if (pread(fd, buffer.chars, tableLength, tableAddress) == tableLength) {
if (readPhysicalMemory(fd, (loff_t) tableAddress, tableLength, buffer.chars)) {
buffer.length = tableLength;
buffer.chars[buffer.length] = '\0';
FF_DEBUG("Successfully read SMBIOS table data: %u bytes", tableLength);
} else {
FF_DEBUG("Failed to read SMBIOS table data: %s", strerror(errno));
FF_DEBUG("Failed to read SMBIOS table data");
return NULL;
}
}