From c5fbfb0a72dd7fb1aa6563347bdc47603df9843f Mon Sep 17 00:00:00 2001
From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Thu, 12 Feb 2026 00:25:31 -0300
Subject: [PATCH] =?utf8?q?feat:=20alarm()=20syscall=20(83)=20=E2=80=94=20p?=
 =?utf8?q?er-process=20SIGALRM=20timer=20via=20scheduler=20tick=20check?=
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---
 include/process.h            |  1 +
 include/syscall.h            |  1 +
 src/kernel/scheduler.c       |  4 ++++
 src/kernel/syscall.c         | 17 +++++++++++++++++
 user/ulibc/include/syscall.h |  1 +
 user/ulibc/include/unistd.h  |  1 +
 user/ulibc/src/unistd.c      |  4 ++++
 7 files changed, 29 insertions(+)

diff --git a/include/process.h b/include/process.h
index 0be6a690..f2d32b70 100644
--- a/include/process.h
+++ b/include/process.h
@@ -66,6 +66,7 @@ struct process {
     int8_t  nice;               // -20 to +19 (maps to priority)
     process_state_t state;
     uint32_t wake_at_tick;
+    uint32_t alarm_tick;
     int exit_status;
 
     int has_user_regs;
diff --git a/include/syscall.h b/include/syscall.h
index adee9486..2cdb5a1c 100644
--- a/include/syscall.h
+++ b/include/syscall.h
@@ -115,6 +115,7 @@ enum {
     SYSCALL_SIGSUSPEND = 80,
     SYSCALL_READV     = 81,
     SYSCALL_WRITEV    = 82,
+    SYSCALL_ALARM     = 83,
 };
 
 #endif
diff --git a/src/kernel/scheduler.c b/src/kernel/scheduler.c
index 9bf571d0..147e7d8d 100644
--- a/src/kernel/scheduler.c
+++ b/src/kernel/scheduler.c
@@ -853,6 +853,10 @@ void process_wake_check(uint32_t current_tick) {
                 rq_enqueue(rq_active, iter);
             }
         }
+        if (iter->alarm_tick != 0 && current_tick >= iter->alarm_tick) {
+            iter->alarm_tick = 0;
+            iter->sig_pending_mask |= (1U << 14); /* SIGALRM */
+        }
         iter = iter->next;
     } while (iter != start);
 
diff --git a/src/kernel/syscall.c b/src/kernel/syscall.c
index 6f647c10..cfc6b941 100644
--- a/src/kernel/syscall.c
+++ b/src/kernel/syscall.c
@@ -2272,6 +2272,23 @@ void syscall_handler(struct registers* regs) {
         return;
     }
 
+    if (syscall_no == SYSCALL_ALARM) {
+        if (!current_process) { regs->eax = 0; return; }
+        uint32_t seconds = regs->ebx;
+        uint32_t now = get_tick_count();
+        uint32_t old_remaining = 0;
+        if (current_process->alarm_tick > now) {
+            old_remaining = (current_process->alarm_tick - now) / 50 + 1;
+        }
+        if (seconds == 0) {
+            current_process->alarm_tick = 0;
+        } else {
+            current_process->alarm_tick = now + seconds * 50;
+        }
+        regs->eax = old_remaining;
+        return;
+    }
+
     if (syscall_no == SYSCALL_SIGSUSPEND) {
         if (!current_process) { regs->eax = (uint32_t)-EINVAL; return; }
         uint32_t new_mask = 0;
diff --git a/user/ulibc/include/syscall.h b/user/ulibc/include/syscall.h
index f43ab027..4598efc3 100644
--- a/user/ulibc/include/syscall.h
+++ b/user/ulibc/include/syscall.h
@@ -74,6 +74,7 @@ enum {
     SYS_SIGSUSPEND = 80,
     SYS_READV = 81,
     SYS_WRITEV = 82,
+    SYS_ALARM = 83,
 };
 
 /* Raw syscall wrappers — up to 5 args via INT 0x80 */
diff --git a/user/ulibc/include/unistd.h b/user/ulibc/include/unistd.h
index af7f24df..6b480f84 100644
--- a/user/ulibc/include/unistd.h
+++ b/user/ulibc/include/unistd.h
@@ -51,6 +51,7 @@ int     setuid(int uid);
 int     setgid(int gid);
 int     truncate(const char* path, int length);
 int     ftruncate(int fd, int length);
+unsigned int alarm(unsigned int seconds);
 void*   brk(void* addr);
 
 void    _exit(int status) __attribute__((noreturn));
diff --git a/user/ulibc/src/unistd.c b/user/ulibc/src/unistd.c
index f1c04483..7ffeb054 100644
--- a/user/ulibc/src/unistd.c
+++ b/user/ulibc/src/unistd.c
@@ -131,6 +131,10 @@ int ftruncate(int fd, int length) {
     return __syscall_ret(_syscall2(SYS_FTRUNCATE, fd, length));
 }
 
+unsigned int alarm(unsigned int seconds) {
+    return (unsigned int)_syscall1(SYS_ALARM, (int)seconds);
+}
+
 void* brk(void* addr) {
     return (void*)_syscall1(SYS_BRK, (int)addr);
 }
-- 
2.43.0