minecraft-pi-reborn/runtime
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Remove PTrace

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This commit is contained in:
TheBrokenRail 2024-06-08 04:46:07 -04:00
parent 50d94d5299
commit 54b79db457
11 changed files with 16 additions and 203 deletions
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2
CMakeLists.txt
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@ -15,6 +15,8 @@ if(NOT TRAMPOLINE_HEADERS_ONLY)
check_symbol_exists("__x86_64__" "" USE_QEMU_TRAMPOLINE)
# Include Correct Sub-Project
set(TRAMPOLINE_RPATH "$ORIGIN/../lib/native")
set(TRAMPOLINE_EXTRA_LINK_FLAG "--disable-new-dtags")
if(USE_NATIVE_TRAMPOLINE)
add_subdirectory(native)
target_compile_definitions(trampoline-headers INTERFACE MCPI_USE_NATIVE_TRAMPOLINE)

5
include/trampoline/types.h
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@ -2,11 +2,10 @@
#include <stdint.h>
// Switch Between Pipe/PTrace Mode
#define TRAMPOLINE_USE_PIPES_ENV "_MCPI_TRAMPOLINE_USE_PIPES"
// Maximum Arguments Length
#define MAX_TRAMPOLINE_ARGS_SIZE 2097152 // 2 MiB
// System Call Constants
#define MAX_TRAMPOLINE_ARGS_SIZE 2097152 // 2 MiB
#define TRAMPOLINE_SYSCALL 0x1337
// Pipe Constants

6
native/CMakeLists.txt
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@ -7,7 +7,7 @@ add_executable(trampoline
src/trampoline.cpp
src/ptrace/loop.cpp
src/ptrace/init.cpp
src/pipe/pipe.cpp
src/pipe.cpp
src/signals.cpp
)
@ -18,8 +18,8 @@ target_compile_options(trampoline PRIVATE -Wall -Wextra -Werror -Wpointer-arith
target_link_libraries(trampoline dl rt trampoline-headers)
# RPath
set_target_properties(trampoline PROPERTIES INSTALL_RPATH "$ORIGIN/../lib/native")
target_link_options(trampoline PRIVATE "LINKER:--disable-new-dtags")
set_target_properties(trampoline PROPERTIES INSTALL_RPATH "${TRAMPOLINE_RPATH}")
target_link_options(trampoline PRIVATE "LINKER:${TRAMPOLINE_EXTRA_LINK_FLAG}")
# Install
function(install_trampoline bin_dir)

16
native/src/main.cpp
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@ -6,8 +6,7 @@
#include "log.h"
#include "memory.h"
#include "trampoline.h"
#include "ptrace/ptrace.h"
#include "pipe/pipe.h"
#include "pipe.h"
#include "signals.h"
// Main
@ -16,11 +15,8 @@ int main(__attribute__((unused)) int argc, char *argv[]) {
if (argc < 2) {
ERR("Invalid Arguments");
}
bool use_ptrace = getenv(TRAMPOLINE_USE_PIPES_ENV) == nullptr;
// Setup
if (!use_ptrace) {
init_pipe_common();
}
// Fork
pid_t pid = fork();
if (pid == -1) {
@ -28,11 +24,7 @@ int main(__attribute__((unused)) int argc, char *argv[]) {
} else if (pid == 0) {
// Setup
setpgid(0, 0);
if (use_ptrace) {
init_ptrace_guest();
} else {
init_pipe_guest();
}
// Execute Program
execvp(argv[1], (char *const *) &argv[1]);
ERR("Unable To Execute Program: %s: %s", argv[1], strerror(errno));
@ -44,11 +36,7 @@ int main(__attribute__((unused)) int argc, char *argv[]) {
init_memory(pid);
init_trampoline();
// Start PTrace
if (use_ptrace) {
init_ptrace_host(pid);
} else {
// Start Pipes
init_pipe_host(pid);
}
}
}

6
native/src/pipe/pipe.cpp → native/src/pipe.cpp
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@ -8,9 +8,9 @@
#include "pipe.h"
#include "../log.h"
#include "../trampoline.h"
#include "../memory.h"
#include "log.h"
#include "trampoline.h"
#include "memory.h"
// Setup Pipes
#define PIPE_READ 0

0
native/src/pipe/pipe.h → native/src/pipe.h
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46
native/src/ptrace/init.cpp
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@ -1,46 +0,0 @@
#include <linux/seccomp.h>
#include <linux/filter.h>
#include <sys/prctl.h>
#include <cstddef>
#include <cerrno>
#include <cstring>
#include <trampoline/types.h>
#include "ptrace.h"
#include "../log.h"
// Init
void init_ptrace_host(pid_t guest_pid) {
// Wait For PTrace
safe_wait(guest_pid, nullptr);
// Configure PTrace
safe_ptrace(PTRACE_SETOPTIONS, guest_pid, nullptr, (void *) (PTRACE_O_EXITKILL | PTRACE_O_TRACESECCOMP));
// Start Loop
loop_ptrace(guest_pid);
}
void init_ptrace_guest() {
// seccomp Filter
sock_filter filter[] = {
// Load Syscall Number To Accumulator
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(seccomp_data, nr)),
// If Syscall Does Not Match The Trampoline, Then Skip The Next Instruction
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, TRAMPOLINE_SYSCALL, 0, 1),
// Trigger PTrace And End Filter
BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_TRACE),
// Allow Syscall And End Filter
BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ALLOW)
};
sock_fprog prog = {
.len = (unsigned short) (sizeof(filter) / sizeof(filter[0])),
.filter = filter
};
// Setup PTrace
safe_ptrace(PTRACE_TRACEME, 0, nullptr, nullptr);
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
ERR("Unable To Prepare Process For Seccomp: %s", strerror(errno));
}
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) == -1) {
ERR("Unable To Set Seccomp Filter: %s", strerror(errno));
}
}

116
native/src/ptrace/loop.cpp
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@ -1,116 +0,0 @@
#include <sys/wait.h>
#include <sys/uio.h>
#include <cstring>
#include <cerrno>
#include <elf.h>
#ifndef __aarch64__
#error "Unsupported Host Architecture"
#endif
#include "ptrace.h"
#include "../log.h"
#include "../trampoline.h"
#include "../memory.h"
// Helper Functions
void safe_ptrace(__ptrace_request request, pid_t pid, void *addr, void *data) {
if (ptrace(request, pid, addr, data) == -1) {
ERR("PTrace Error: %s", strerror(errno));
}
}
void safe_wait(pid_t guest_pid, int *status) {
int real_status;
if (waitpid(guest_pid, &real_status, 0) == -1) {
ERR("Unable To Wait For Guest");
}
if (WIFEXITED(real_status)) {
// Process Exited
exit(WEXITSTATUS(real_status));
}
if (status != nullptr) {
*status = real_status;
}
}
static void ptrace_wait_syscall(pid_t guest_pid) {
while (true) {
safe_ptrace(PTRACE_CONT, guest_pid, nullptr, nullptr);
int status;
safe_wait(guest_pid, &status);
if ((status >> 8) == (SIGTRAP | (PTRACE_EVENT_SECCOMP << 8))) {
return;
}
}
}
// Registers
struct arm32_pt_regs {
uint32_t regs[18];
};
static bool check_syscall(pid_t guest_pid, arm32_pt_regs *out) {
// Read Registers
arm32_pt_regs regs = {};
iovec io = {
.iov_base = &regs,
.iov_len = sizeof(regs)
};
safe_ptrace(PTRACE_GETREGSET, guest_pid, (void *) NT_PRSTATUS, &io);
if (io.iov_len != sizeof(regs)) {
ERR("Guest Must Be 32-Bit");
}
// Check Syscall
if (regs.regs[7] != TRAMPOLINE_SYSCALL) {
// Not Trampoline
return false;
}
// Block Syscall
int new_syscall = -1;
iovec syscall_io = {
.iov_base = &new_syscall,
.iov_len = sizeof(int),
};
safe_ptrace(PTRACE_SETREGSET, guest_pid, (void *) NT_ARM_SYSTEM_CALL, &syscall_io);
// Export Registers
*out = regs;
// Return
return true;
}
static void get_arguments(arm32_pt_regs *regs, uint32_t *arg1, uint32_t *arg2, uint32_t *arg3) {
*arg1 = regs->regs[0];
*arg2 = regs->regs[1];
*arg3 = regs->regs[2];
}
static void set_syscall_return(pid_t guest_pid, arm32_pt_regs *regs) {
regs->regs[0] = 0;
iovec io = {
.iov_base = regs,
.iov_len = sizeof(arm32_pt_regs)
};
safe_ptrace(PTRACE_SETREGSET, guest_pid, (void *) NT_PRSTATUS, &io);
}
// Main Loop
void loop_ptrace(pid_t guest_pid) {
while (true) {
// Wait For Syscall
ptrace_wait_syscall(guest_pid);
// Handle Syscall
arm32_pt_regs regs = {};
bool is_trampoline = check_syscall(guest_pid, &regs);
if (is_trampoline) {
// Get Arguments
uint32_t id;
uint32_t length;
uint32_t args_addr;
get_arguments(&regs, &id, &length, &args_addr);
unsigned char args[MAX_TRAMPOLINE_ARGS_SIZE];
memory_reader(args_addr, args, length);
// Run Trampoline
const uint32_t ret = trampoline(id, args);
memory_writer(args_addr, &ret, sizeof(uint32_t));
// Set Syscall Return
set_syscall_return(guest_pid, &regs);
}
}
}

10
native/src/ptrace/ptrace.h
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@ -1,10 +0,0 @@
#pragma once
#include <sys/types.h>
#include <sys/ptrace.h>
void safe_ptrace(__ptrace_request request, pid_t pid, void *addr, void *data);
void safe_wait(pid_t guest_pid, int *status);
void init_ptrace_host(pid_t guest_pid);
void init_ptrace_guest();
void loop_ptrace(pid_t guest_pid);

4
native/src/signals.cpp
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@ -2,10 +2,6 @@
#include "signals.h"
#include <cstdio>
#include <cstring>
#include <cerrno>
// Signal Handlers
static pid_t guest_pid = -1;
static void exit_handler(__attribute__((unused)) int signal_id) {

2
qemu/CMakeLists.txt
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@ -36,7 +36,7 @@ ExternalProject_Add(qemu
"--cross-prefix="
"--cc=${CMAKE_C_COMPILER}"
"--cxx=${CMAKE_CXX_COMPILER}"
"--extra-ldflags=-ldl -Wl,-rpath=$ORIGIN/../lib/native -Wl,--disable-new-dtags"
"--extra-ldflags=-ldl -Wl,-rpath=${TRAMPOLINE_RPATH} -Wl,${TRAMPOLINE_EXTRA_LINK_FLAG}"
"--disable-debug-info"
"--target-list=arm-linux-user"
"--without-default-features"