Support alternate signal stack

regression/apps/signal_c/signal_test.c

@@ -265,6 +265,7 @@ int test_sigchld() {
         // child process
         printf("create a new proces successfully (pid = %d)\n", getpid());
         fflush(stdout);
+        exit(0);
     } else {
         // parent process
         wait(NULL);
@@ -274,11 +275,82 @@ int test_sigchld() {
     return 0;
 }
 
+// ============================================================================
+// Test handle signal on alternate signal stack
+// ============================================================================
+
+#define MAX_ALTSTACK_RECURSION_LEVEL    2
+
+stack_t g_old_ss;
+
+static void handle_sigpipe(int num, siginfo_t *info, void *context) {
+    static volatile int recursion_level = 0;
+    printf("Hello from SIGPIPE signal handler on the alternate signal stack (recursion_level = %d)\n",
+           recursion_level);
+
+    // save old_ss to check if we are on stack
+    stack_t old_ss;
+    sigaltstack(NULL, &old_ss);
+    g_old_ss = old_ss;
+
+    recursion_level++;
+    if (recursion_level <= MAX_ALTSTACK_RECURSION_LEVEL) {
+        raise(SIGPIPE);
+    }
+    recursion_level--;
+}
+
+#define SIGSTACKSIZE (4*4096)
+
+int test_sigaltstack() {
+    static char stack[SIGSTACKSIZE];
+    stack_t expected_ss = {
+        .ss_size = SIGSTACKSIZE,
+        .ss_sp = stack,
+        .ss_flags = 0,
+    };
+    if (sigaltstack(&expected_ss, NULL) < 0) {
+        THROW_ERROR("failed to call sigaltstack");
+    }
+    stack_t actual_ss;
+    if (sigaltstack(NULL, &actual_ss) < 0) {
+        THROW_ERROR("failed to call sigaltstack");
+    }
+    if (actual_ss.ss_size != expected_ss.ss_size
+            || actual_ss.ss_sp != expected_ss.ss_sp
+            || actual_ss.ss_flags != expected_ss.ss_flags) {
+        THROW_ERROR("failed to check the signal stack after set");
+    }
+
+    struct sigaction new_action, old_action;
+    memset(&new_action, 0, sizeof(struct sigaction));
+    memset(&old_action, 0, sizeof(struct sigaction));
+    new_action.sa_sigaction = handle_sigpipe;
+    new_action.sa_flags = SA_SIGINFO | SA_NODEFER | SA_ONSTACK;
+    if (sigaction(SIGPIPE, &new_action, &old_action) < 0) {
+        THROW_ERROR("registering new signal handler failed");
+    }
+    if (old_action.sa_handler != SIG_DFL) {
+        THROW_ERROR("unexpected old sig handler");
+    }
+
+    raise(SIGPIPE);
+    if (g_old_ss.ss_flags != SS_ONSTACK) {
+        THROW_ERROR("check stack flags failed");
+    }
+
+    if (sigaction(SIGPIPE, &old_action, NULL) < 0) {
+        THROW_ERROR("restoring old signal handler failed");
+    }
+    return 0;
+}
+
 int main() {
     test_sigprocmask();
     test_raise();
     test_handle_sigfpe();
     test_handle_sigsegv();
     test_sigchld();
+    test_sigaltstack();
     return 0;
 }

services/libs/jinux-std/src/process/posix_thread/builder.rs

@@ -92,7 +92,6 @@ impl PosixThreadBuilder {
         let thread = Arc::new_cyclic(|thread_ref| {
             let task = create_new_user_task(user_space, thread_ref.clone());
             let status = ThreadStatus::Init;
-            let sig_context = Mutex::new(None);
             let posix_thread = PosixThread {
                 process,
                 is_main_thread,
@@ -102,7 +101,8 @@ impl PosixThreadBuilder {
                 credentials,
                 sig_mask: Mutex::new(sig_mask),
                 sig_queues: Mutex::new(sig_queues),
-                sig_context,
+                sig_context: Mutex::new(None),
+                sig_stack: Mutex::new(None),
                 robust_list: Mutex::new(None),
             };
 

services/libs/jinux-std/src/process/posix_thread/mod.rs

@@ -3,7 +3,7 @@ use super::signal::sig_mask::SigMask;
 use super::signal::sig_num::SigNum;
 use super::signal::sig_queues::SigQueues;
 use super::signal::signals::Signal;
-use super::signal::{SigEvents, SigEventsFilter};
+use super::signal::{SigEvents, SigEventsFilter, SigStack};
 use super::{do_exit_group, Credentials, Process, TermStatus};
 use crate::events::Observer;
 use crate::prelude::*;
@@ -51,6 +51,7 @@ pub struct PosixThread {
     /// Signal handler ucontext address
     /// FIXME: This field may be removed. For glibc applications with RESTORER flag set, the sig_context is always equals with rsp.
     sig_context: Mutex<Option<Vaddr>>,
+    sig_stack: Mutex<Option<SigStack>>,
 }
 
 impl PosixThread {
@@ -152,6 +153,10 @@ impl PosixThread {
         &self.sig_context
     }
 
+    pub fn sig_stack(&self) -> &Mutex<Option<SigStack>> {
+        &self.sig_stack
+    }
+
     pub fn robust_list(&self) -> &Mutex<Option<RobustListHead>> {
         &self.robust_list
     }

services/libs/jinux-std/src/process/signal/mod.rs

@@ -8,30 +8,27 @@ pub mod sig_disposition;
 pub mod sig_mask;
 pub mod sig_num;
 pub mod sig_queues;
+mod sig_stack;
 pub mod signals;
 
 pub use events::{SigEvents, SigEventsFilter};
 pub use pauser::Pauser;
 pub use poll::{Pollee, Poller};
-
-use core::mem;
+pub use sig_stack::{SigStack, SigStackFlags, SigStackStatus};
 
 use align_ext::AlignExt;
-use jinux_frame::{cpu::UserContext, task::Task};
+use core::mem;
+use jinux_frame::cpu::UserContext;
+use jinux_frame::task::Task;
 
-use self::c_types::siginfo_t;
-use self::sig_mask::SigMask;
-use self::sig_num::SigNum;
-use crate::current_thread;
-use crate::process::posix_thread::PosixThreadExt;
-use crate::process::signal::c_types::ucontext_t;
-use crate::process::signal::sig_action::SigActionFlags;
+use super::posix_thread::{PosixThread, PosixThreadExt};
+use crate::prelude::*;
 use crate::process::{do_exit_group, TermStatus};
 use crate::util::{write_bytes_to_user, write_val_to_user};
-use crate::{
-    prelude::*,
-    process::signal::sig_action::{SigAction, SigDefaultAction},
-};
+use c_types::{siginfo_t, ucontext_t};
+use sig_action::{SigAction, SigActionFlags, SigDefaultAction};
+use sig_mask::SigMask;
+use sig_num::SigNum;
 
 /// Handle pending signal for current process
 pub fn handle_pending_signal(context: &mut UserContext) -> Result<()> {
@@ -134,19 +131,24 @@ pub fn handle_user_signal(
     // block signals in sigmask when running signal handler
     posix_thread.sig_mask().lock().block(mask.as_u64());
 
-    // Set up signal stack in user stack,
-    // to avoid corrupting user stack, we minus 128 first.
-    let mut user_rsp = context.rsp() as u64;
-    user_rsp -= 128;
+    // Set up signal stack.
+    let mut stack_pointer = if let Some(sp) = use_alternate_signal_stack(posix_thread) {
+        sp as u64
+    } else {
+        // just use user stack
+        context.rsp() as u64
+    };
+
+    // To avoid corrupting signal stack, we minus 128 first.
+    stack_pointer -= 128;
 
     // 1. write siginfo_t
-    user_rsp -= mem::size_of::<siginfo_t>() as u64;
-    write_val_to_user(user_rsp as _, &sig_info)?;
-    let siginfo_addr = user_rsp;
-    // debug!("siginfo_addr = 0x{:x}", siginfo_addr);
+    stack_pointer -= mem::size_of::<siginfo_t>() as u64;
+    write_val_to_user(stack_pointer as _, &sig_info)?;
+    let siginfo_addr = stack_pointer;
 
     // 2. write ucontext_t.
-    user_rsp = alloc_aligned_in_user_stack(user_rsp, mem::size_of::<ucontext_t>(), 16)?;
+    stack_pointer = alloc_aligned_in_user_stack(stack_pointer, mem::size_of::<ucontext_t>(), 16)?;
     let mut ucontext = ucontext_t {
         uc_sigmask: mask.as_u64(),
         ..Default::default()
@@ -159,18 +161,17 @@ pub fn handle_user_signal(
         ucontext.uc_link = 0;
     }
     // TODO: store fp regs in ucontext
-    write_val_to_user(user_rsp as _, &ucontext)?;
-    let ucontext_addr = user_rsp;
-    // Store the ucontext addr in sig context of current process.
+    write_val_to_user(stack_pointer as _, &ucontext)?;
+    let ucontext_addr = stack_pointer;
+    // Store the ucontext addr in sig context of current thread.
     *sig_context = Some(ucontext_addr as Vaddr);
-    // current.sig_context().lock().push_back(ucontext_addr as _);
 
     // 3. Set the address of the trampoline code.
     if flags.contains(SigActionFlags::SA_RESTORER) {
         // If contains SA_RESTORER flag, trampoline code is provided by libc in restorer_addr.
         // We just store restorer_addr on user stack to allow user code just to trampoline code.
-        user_rsp = write_u64_to_user_stack(user_rsp, restorer_addr as u64)?;
-        trace!("After set restorer addr: user_rsp = 0x{:x}", user_rsp);
+        stack_pointer = write_u64_to_user_stack(stack_pointer, restorer_addr as u64)?;
+        trace!("After set restorer addr: user_rsp = 0x{:x}", stack_pointer);
     } else {
         // Otherwise we create a trampoline.
         // FIXME: This may cause problems if we read old_context from rsp.
@@ -179,14 +180,14 @@ pub fn handle_user_signal(
             0x0f, 0x05, // syscall (call rt_sigreturn)
             0x90, // nop (for alignment)
         ];
-        user_rsp -= TRAMPOLINE.len() as u64;
-        let trampoline_rip = user_rsp;
-        write_bytes_to_user(user_rsp as Vaddr, TRAMPOLINE)?;
-        user_rsp = write_u64_to_user_stack(user_rsp, trampoline_rip)?;
+        stack_pointer -= TRAMPOLINE.len() as u64;
+        let trampoline_rip = stack_pointer;
+        write_bytes_to_user(stack_pointer as Vaddr, TRAMPOLINE)?;
+        stack_pointer = write_u64_to_user_stack(stack_pointer, trampoline_rip)?;
     }
     // 4. Set correct register values
     context.set_rip(handler_addr as _);
-    context.set_rsp(user_rsp as usize);
+    context.set_rsp(stack_pointer as usize);
     // parameters of signal handler
     context.set_rdi(sig_num.as_u8() as usize); // signal number
     if flags.contains(SigActionFlags::SA_SIGINFO) {
@@ -200,6 +201,34 @@ pub fn handle_user_signal(
     Ok(())
 }
 
+/// Use an alternate signal stack, which was installed by sigaltstack.
+/// It the stack is already active, we just increase the handler counter and return None, since
+/// the stack pointer can be read from context.
+/// It the stack is not used by any handler, we will return the new sp in alternate signal stack.
+fn use_alternate_signal_stack(posix_thread: &PosixThread) -> Option<usize> {
+    let mut sig_stack = posix_thread.sig_stack().lock();
+
+    let Some(sig_stack) = &mut *sig_stack else {
+        return None;
+    };
+
+    if sig_stack.is_disabled() {
+        return None;
+    }
+
+    if sig_stack.is_active() {
+        // The stack is already active, so we just use sp in context.
+        sig_stack.increase_handler_counter();
+        return None;
+    }
+
+    sig_stack.increase_handler_counter();
+
+    // Make sp align at 16. FIXME: is this required?
+    let stack_pointer = (sig_stack.base() + sig_stack.size()).align_down(16);
+    Some(stack_pointer)
+}
+
 fn write_u64_to_user_stack(rsp: u64, value: u64) -> Result<u64> {
     let rsp = rsp - 8;
     write_val_to_user(rsp as Vaddr, &value)?;

services/libs/jinux-std/src/process/signal/sig_action.rs

@@ -103,7 +103,6 @@ impl SigActionFlags {
         self.intersects(
             SigActionFlags::SA_NOCLDSTOP
                 | SigActionFlags::SA_NOCLDWAIT
-                | SigActionFlags::SA_ONSTACK
                 | SigActionFlags::SA_RESETHAND,
         )
     }

services/libs/jinux-std/src/process/signal/sig_stack.rs

@@ -0,0 +1,93 @@
+use crate::prelude::*;
+
+/// User-provided signal stack. `SigStack` is per-thread, and each thread can have
+/// at most one `SigStack`. If one signal handler specifying the `SA_ONSTACK` flag,
+/// the handler should be executed on the `SigStack`, instead of on the default stack.
+///
+/// SigStack can be registered and unregistered by syscall `sigaltstack`.
+#[derive(Debug, Clone)]
+pub struct SigStack {
+    base: Vaddr,
+    flags: SigStackFlags,
+    size: usize,
+    /// The number of handlers that are currently using the stack
+    handler_counter: usize,
+}
+
+bitflags! {
+    pub struct SigStackFlags: u32 {
+        const SS_AUTODISARM = 1 << 31;
+    }
+}
+
+#[repr(u8)]
+#[allow(non_camel_case_types)]
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub enum SigStackStatus {
+    #[default]
+    SS_INACTIVE = 0,
+    // The thread is currently executing on the alternate signal stack
+    SS_ONSTACK = 1,
+    // The stack is currently disabled.
+    SS_DISABLE = 2,
+}
+
+impl SigStack {
+    pub fn new(base: Vaddr, flags: SigStackFlags, size: usize) -> Self {
+        Self {
+            base,
+            flags,
+            size,
+            handler_counter: 0,
+        }
+    }
+
+    pub fn base(&self) -> Vaddr {
+        self.base
+    }
+
+    pub fn flags(&self) -> SigStackFlags {
+        self.flags
+    }
+
+    pub fn size(&self) -> usize {
+        self.size
+    }
+
+    pub fn status(&self) -> SigStackStatus {
+        if self.handler_counter == 0 {
+            return SigStackStatus::SS_INACTIVE;
+        }
+
+        // Learning From [sigaltstack doc](https://man7.org/linux/man-pages/man2/sigaltstack.2.html):
+        // If the stack is currently executed on,
+        // 1. If the stack was established with flag SS_AUTODISARM, the stack status is DISABLE,
+        // 2. otherwise, the stack status is ONSTACK
+        if self.flags.contains(SigStackFlags::SS_AUTODISARM) {
+            SigStackStatus::SS_DISABLE
+        } else {
+            SigStackStatus::SS_ONSTACK
+        }
+    }
+
+    /// Mark the stack is currently used by a signal handler.    
+    pub fn increase_handler_counter(&mut self) {
+        self.handler_counter += 1;
+    }
+
+    // Mark the stack is freed by current handler.
+    pub fn decrease_handler_counter(&mut self) {
+        // FIXME: deal with SS_AUTODISARM flag
+        self.handler_counter -= 1
+    }
+
+    /// Determins whether the stack is executed on by any signal handler
+    pub fn is_active(&self) -> bool {
+        // FIXME: can DISABLE stack be used?
+        self.handler_counter != 0 && !self.flags.contains(SigStackFlags::SS_AUTODISARM)
+    }
+
+    pub fn is_disabled(&self) -> bool {
+        self.handler_counter != 0 && self.flags.contains(SigStackFlags::SS_AUTODISARM)
+    }
+}

services/libs/jinux-std/src/syscall/mod.rs

@@ -99,6 +99,7 @@ use self::setsid::sys_setsid;
 use self::setsockopt::sys_setsockopt;
 use self::setuid::sys_setuid;
 use self::shutdown::sys_shutdown;
+use self::sigaltstack::sys_sigaltstack;
 use self::socket::sys_socket;
 use self::socketpair::sys_socketpair;
 
@@ -185,6 +186,7 @@ mod setsid;
 mod setsockopt;
 mod setuid;
 mod shutdown;
+mod sigaltstack;
 mod socket;
 mod socketpair;
 mod stat;
@@ -316,6 +318,7 @@ define_syscall_nums!(
     SYS_SETFSUID = 122,
     SYS_SETFSGID = 123,
     SYS_GETSID = 124,
+    SYS_SIGALTSTACK = 131,
     SYS_STATFS = 137,
     SYS_FSTATFS = 138,
     SYS_PRCTL = 157,
@@ -491,6 +494,7 @@ pub fn syscall_dispatch(
         SYS_SETFSUID => syscall_handler!(1, sys_setfsuid, args),
         SYS_SETFSGID => syscall_handler!(1, sys_setfsgid, args),
         SYS_GETSID => syscall_handler!(1, sys_getsid, args),
+        SYS_SIGALTSTACK => syscall_handler!(2, sys_sigaltstack, args),
         SYS_STATFS => syscall_handler!(2, sys_statfs, args),
         SYS_FSTATFS => syscall_handler!(2, sys_fstatfs, args),
         SYS_PRCTL => syscall_handler!(5, sys_prctl, args),

services/libs/jinux-std/src/syscall/rt_sigreturn.rs

@@ -23,6 +23,15 @@ pub fn sys_rt_sigreturn(context: &mut UserContext) -> Result<SyscallReturn> {
     debug_assert!(sig_context_addr == context.rsp() as Vaddr);
 
     let ucontext = read_val_from_user::<ucontext_t>(sig_context_addr)?;
+
+    // If the sig stack is active and used by current handler, decrease handler counter.
+    if let Some(sig_stack) = posix_thread.sig_stack().lock().as_mut() {
+        let rsp = context.rsp();
+        if rsp >= sig_stack.base() && rsp <= sig_stack.base() + sig_stack.size() {
+            sig_stack.decrease_handler_counter();
+        }
+    }
+
     // Set previous ucontext address
     if ucontext.uc_link == 0 {
         *sig_context = None;
@@ -33,5 +42,6 @@ pub fn sys_rt_sigreturn(context: &mut UserContext) -> Result<SyscallReturn> {
     // unblock sig mask
     let sig_mask = ucontext.uc_sigmask;
     posix_thread.sig_mask().lock().unblock(sig_mask);
+
     Ok(SyscallReturn::NoReturn)
 }

services/libs/jinux-std/src/syscall/sigaltstack.rs

@@ -0,0 +1,112 @@
+use crate::log_syscall_entry;
+use crate::prelude::*;
+use crate::process::posix_thread::PosixThreadExt;
+use crate::process::signal::SigStack;
+use crate::process::signal::SigStackFlags;
+use crate::util::read_val_from_user;
+use crate::util::write_val_to_user;
+
+use super::{SyscallReturn, SYS_SIGALTSTACK};
+
+pub fn sys_sigaltstack(sig_stack_addr: Vaddr, old_sig_stack_addr: Vaddr) -> Result<SyscallReturn> {
+    log_syscall_entry!(SYS_SIGALTSTACK);
+
+    debug!(
+        "sig_stack_addr = 0x{:x}, old_sig_stack_addr: 0x{:x}",
+        sig_stack_addr, old_sig_stack_addr
+    );
+
+    let old_stack = {
+        let current_thread = current_thread!();
+        let posix_thread = current_thread.as_posix_thread().unwrap();
+        let sig_stack = posix_thread.sig_stack().lock();
+        sig_stack.clone()
+    };
+
+    get_old_stack(old_sig_stack_addr, old_stack.as_ref())?;
+    set_new_stack(sig_stack_addr, old_stack.as_ref())?;
+
+    Ok(SyscallReturn::Return(0))
+}
+
+fn get_old_stack(old_sig_stack_addr: Vaddr, old_stack: Option<&SigStack>) -> Result<()> {
+    if old_sig_stack_addr == 0 {
+        return Ok(());
+    }
+
+    let Some(old_stack) = old_stack else {
+        return Ok(());
+    };
+
+    debug!("old stack = {:?}", old_stack);
+
+    let stack = stack_t::from(old_stack.clone());
+    write_val_to_user(old_sig_stack_addr, &stack)
+}
+
+fn set_new_stack(sig_stack_addr: Vaddr, old_stack: Option<&SigStack>) -> Result<()> {
+    if sig_stack_addr == 0 {
+        return Ok(());
+    }
+
+    if let Some(old_stack) = old_stack && old_stack.is_active() {
+        return_errno_with_message!(Errno::EPERM, "the old stack is active now");
+    }
+
+    let new_stack = {
+        let stack = read_val_from_user::<stack_t>(sig_stack_addr)?;
+        SigStack::try_from(stack)?
+    };
+
+    debug!("new_stack = {:?}", new_stack);
+
+    let current_thread = current_thread!();
+    let posix_thread = current_thread.as_posix_thread().unwrap();
+    *posix_thread.sig_stack().lock() = Some(new_stack);
+
+    Ok(())
+}
+
+#[allow(non_camel_case_types)]
+#[derive(Debug, Clone, Copy, Pod)]
+#[repr(C)]
+struct stack_t {
+    // Base address of stack
+    sp: Vaddr,
+    flags: i32,
+    // Number of bytes in stack
+    size: usize,
+}
+
+impl TryFrom<stack_t> for SigStack {
+    type Error = Error;
+
+    fn try_from(stack: stack_t) -> Result<Self> {
+        if stack.flags < 0 {
+            return_errno_with_message!(Errno::EINVAL, "negative flags");
+        }
+
+        let flags = SigStackFlags::from_bits(stack.flags as u32)
+            .ok_or_else(|| Error::with_message(Errno::EINVAL, "invalid flags"))?;
+
+        if stack.size < MINSTKSZ {
+            return_errno_with_message!(Errno::ENOMEM, "stack size is less than MINSTKSZ");
+        }
+
+        Ok(Self::new(stack.sp, flags, stack.size))
+    }
+}
+
+impl From<SigStack> for stack_t {
+    fn from(stack: SigStack) -> Self {
+        let flags = stack.flags().bits() as i32 | stack.status() as i32;
+        Self {
+            sp: stack.base(),
+            flags,
+            size: stack.size(),
+        }
+    }
+}
+
+const SIGSTKSZ: usize = 8192;
+const MINSTKSZ: usize = 2048;