From 85480faf9a155ccc280b817f5cfa76eafe082837 Mon Sep 17 00:00:00 2001
From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Thu, 12 Feb 2026 01:05:00 -0300
Subject: [PATCH] =?utf8?q?feat:=20flock()=20syscall=20(87)=20=E2=80=94=20a?=
 =?utf8?q?dvisory=20file=20locking=20no-op=20stub=20+=20ulibc=20wrapper?=
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---
 include/syscall.h            |  1 +
 src/kernel/syscall.c         | 10 ++++++++++
 user/ulibc/include/syscall.h |  1 +
 user/ulibc/include/unistd.h  |  5 +++++
 user/ulibc/src/unistd.c      |  4 ++++
 5 files changed, 21 insertions(+)

diff --git a/include/syscall.h b/include/syscall.h
index 9f16ebc..33d63ba 100644
--- a/include/syscall.h
+++ b/include/syscall.h
@@ -110,6 +110,7 @@ enum {
     SYSCALL_TIMES     = 84,
     SYSCALL_FUTEX     = 85,
     SYSCALL_SIGALTSTACK = 86,
+    SYSCALL_FLOCK     = 87,
 };
 
 #endif
diff --git a/src/kernel/syscall.c b/src/kernel/syscall.c
index c2940b7..b876c4e 100644
--- a/src/kernel/syscall.c
+++ b/src/kernel/syscall.c
@@ -2272,6 +2272,16 @@ void syscall_handler(struct registers* regs) {
         return;
     }
 
+    if (syscall_no == SYSCALL_FLOCK) {
+        int fd = (int)regs->ebx;
+        if (!current_process || fd < 0 || fd >= PROCESS_MAX_FILES || !current_process->files[fd]) {
+            regs->eax = (uint32_t)-EBADF;
+        } else {
+            regs->eax = 0; /* advisory lock — no-op stub */
+        }
+        return;
+    }
+
     if (syscall_no == SYSCALL_SIGALTSTACK ||
         syscall_no == SYSCALL_TIMES || syscall_no == SYSCALL_FUTEX) {
         posix_ext_syscall_dispatch(regs, syscall_no);
diff --git a/user/ulibc/include/syscall.h b/user/ulibc/include/syscall.h
index 568e79f..f322fdd 100644
--- a/user/ulibc/include/syscall.h
+++ b/user/ulibc/include/syscall.h
@@ -69,6 +69,7 @@ enum {
     SYS_TIMES = 84,
     SYS_FUTEX = 85,
     SYS_SIGALTSTACK = 86,
+    SYS_FLOCK = 87,
 };
 
 /* 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 e2bb132..e993417 100644
--- a/user/ulibc/include/unistd.h
+++ b/user/ulibc/include/unistd.h
@@ -43,6 +43,11 @@ int     setgid(int gid);
 int     truncate(const char* path, int length);
 int     ftruncate(int fd, int length);
 unsigned int alarm(unsigned int seconds);
+#define LOCK_SH 1
+#define LOCK_EX 2
+#define LOCK_UN 8
+#define LOCK_NB 4
+int     flock(int fd, int operation);
 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 609de9f..8d6294c 100644
--- a/user/ulibc/src/unistd.c
+++ b/user/ulibc/src/unistd.c
@@ -126,6 +126,10 @@ unsigned int alarm(unsigned int seconds) {
     return (unsigned int)_syscall1(SYS_ALARM, (int)seconds);
 }
 
+int flock(int fd, int operation) {
+    return __syscall_ret(_syscall2(SYS_FLOCK, fd, operation));
+}
+
 void* brk(void* addr) {
     return (void*)_syscall1(SYS_BRK, (int)addr);
 }
-- 
2.43.0