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fix(guest-arena): throw when the Linux reservation cannot be placed 

Throw when /proc/self/maps cannot be read or parsed, and when the kernel
places a reservation chunk at another address (MAP_FIXED_NOREPLACE
treated as a hint). Remove the unused PageSize and keep the POSIX-only
headers in the non-Windows block.
This commit is contained in:
Dean Galvin 2026-10-10 22:40:00 +13:00
parent d9f8400351
commit cf85a72024
1 changed files with 11 additions and 16 deletions
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27
core/libs/prx/libc/src/GuestArena.cpp
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@ -5,12 +5,12 @@
#include <atomic>
#include <cstdint>
#ifndef _WIN32
#include <unistd.h>
#include <cerrno>
#include <fstream>
#include <sstream>
#include <string>
#include <sys/mman.h>
#endif
#include <sstream>
#include <fstream>
#include <cstdio>
#include <iterator>
#include <map>
@ -167,12 +167,13 @@ private:
#if defined(__linux__)
void SeedLinuxUsedRanges() {
std::ifstream maps("/proc/self/maps");
if (!maps.is_open()) throw std::runtime_error("guest arena: cannot open /proc/self/maps");
std::string line;
while (std::getline(maps, line)) {
std::istringstream fields(line);
std::uintptr_t begin = 0, end = 0;
char dash = 0;
if (!(fields >> std::hex >> begin >> dash >> end) || end <= begin) continue;
if (!(fields >> std::hex >> begin >> dash >> end) || dash != '-' || end <= begin) throw std::runtime_error("guest arena: malformed /proc/self/maps line: " + line);
if (end <= ArenaStart || begin >= ApplicationAreaEnd) continue;
const auto first = std::max(begin, ArenaStart);
const auto last = std::min(end, ApplicationAreaEnd);
@ -190,10 +191,12 @@ private:
constexpr std::uintptr_t kChunk = 1ULL << 30;
for (std::uintptr_t cursor = from; cursor < to; cursor += kChunk) {
const auto end = std::min(cursor + kChunk, to);
if (mmap(reinterpret_cast<void*>(cursor), end - cursor, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_FIXED_NOREPLACE, -1, 0) != MAP_FAILED)
continue;
const int failed = errno;
void* const wanted = reinterpret_cast<void*>(cursor);
void* const placed = mmap(wanted, end - cursor, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_FIXED_NOREPLACE, -1, 0);
if (placed == wanted) continue;
const int failed = placed == MAP_FAILED ? errno : EINVAL;
if (placed != MAP_FAILED) munmap(placed, end - cursor);
if (failed != EEXIST) {
char message[128];
std::snprintf(message, sizeof(message), "guest arena: cannot reserve 0x%llx+0x%llx",
@ -219,14 +222,6 @@ private:
_hostRegions.emplace_back(from, to);
}
}
static std::uintptr_t PageSize() {
static const std::uintptr_t value = [] {
const long configured = sysconf(_SC_PAGESIZE);
return configured > 0 ? static_cast<std::uintptr_t>(configured) : 4096u;
}();
return value;
}
#endif
std::mutex _lock;