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UserspaceEmulator: Add support for UNIX signals :^)

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The emulator will now register signal handlers for all possible signals
and act as a translation layer between the kernel and the emulated
process.

To get an accurate simulation of signal handling, we duplicate the same
trampoline mechanism used by the kernel's signal delivery system, and
also use the "sigreturn" syscall to return from a signal handler.

Signal masking is not fully implemented yet, but this is pretty cool!
This commit is contained in:
Andreas Kling 2020-08-05 19:36:24 +02:00
parent ce95628b7f
commit 8dea25d974
3 changed files with 269 additions and 0 deletions
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22
DevTools/UserspaceEmulator/Emulator.h
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@ -33,6 +33,7 @@
#include <LibDebug/DebugInfo.h>
#include <LibELF/Loader.h>
#include <LibX86/Instruction.h>
#include <signal.h>
#include <sys/types.h>
namespace UserspaceEmulator {
@ -59,6 +60,8 @@ public:
bool is_in_malloc_or_free() const;
void did_receive_signal(int signum) { m_pending_signals |= (1 << signum); }
private:
NonnullRefPtr<ELF::Loader> m_elf;
OwnPtr<DebugInfo> m_debug_info;
@ -69,9 +72,13 @@ private:
OwnPtr<MallocTracer> m_malloc_tracer;
void setup_stack(const Vector<String>& arguments, const Vector<String>& environment);
void register_signal_handlers();
void setup_signal_trampoline();
int virt$fork();
int virt$execve(FlatPtr);
int virt$sigaction(int, FlatPtr, FlatPtr);
int virt$sigreturn();
int virt$get_dir_entries(int fd, FlatPtr buffer, ssize_t);
int virt$ioctl(int fd, unsigned, FlatPtr);
int virt$stat(FlatPtr);
@ -128,9 +135,12 @@ private:
int virt$connect(int sockfd, FlatPtr address, socklen_t address_size);
void virt$exit(int);
ssize_t virt$getrandom(FlatPtr buffer, size_t buffer_size, unsigned int flags);
int virt$sleep(unsigned);
FlatPtr allocate_vm(size_t size, size_t alignment);
void dispatch_one_pending_signal();
bool m_shutdown { false };
int m_exit_status { 0 };
@ -138,6 +148,18 @@ private:
FlatPtr m_malloc_symbol_end { 0 };
FlatPtr m_free_symbol_start { 0 };
FlatPtr m_free_symbol_end { 0 };
sigset_t m_pending_signals { 0 };
sigset_t m_signal_mask { 0 };
struct SignalHandlerInfo {
FlatPtr handler { 0 };
sigset_t mask { 0 };
int flags { 0 };
};
SignalHandlerInfo m_signal_handler[NSIG];
FlatPtr m_signal_trampoline { 0 };
};
void report(const char*, ...);