From: Matthias Kruk <m@m10k.eu>
Date: Mon, 2 Dec 2019 08:12:40 +0000 (+0900)
Subject: Implement sbrk() POSIX syscall
X-Git-Url: https://git.corax.cc/?a=commitdiff_plain;h=67e8287d7033a2e9dac0cf8ff2ef1f729f269720;p=corax

Implement sbrk() POSIX syscall
 - Implement sys_sbrk() syscall handler
 - Add brk() and sbrk() syscall stubs to klibc
 - Add prototypes for brk() and sbrk() to unistd.h
---

diff --git a/include/corax/syscall.h b/include/corax/syscall.h
index d8e20df..ba39618 100644
--- a/include/corax/syscall.h
+++ b/include/corax/syscall.h
@@ -23,6 +23,7 @@
 #define SYS_WAITID     5
 #define SYS_SETSID     6
 #define SYS_SLEEP      7
+#define SYS_SBRK       8
 
 /* Corax-specific variations of POSIX syscalls */
 #define SYS_EXECFVE    128
diff --git a/include/unistd.h b/include/unistd.h
index 5c9d929..4b87539 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -8,5 +8,7 @@ extern pid_t fork(void);
 extern pid_t vfork(void);
 extern int execfve(void*, const char**, const char**);
 extern unsigned int sleep(unsigned int);
+extern int brk(void*);
+extern void* sbrk(int);
 
 #endif /* _UNISTD_H */
diff --git a/kernel/core/posixcall.c b/kernel/core/posixcall.c
index 76a8fcc..8d3985d 100644
--- a/kernel/core/posixcall.c
+++ b/kernel/core/posixcall.c
@@ -49,6 +49,27 @@ int sys_fork(stack_frame_t *stk)
 	return(ret_val);
 }
 
+int sys_sbrk(ssize_t increment)
+{
+	process_t *cproc;
+	pg_dir_t *pgdir;
+	int ret_val;
+
+	cproc = process_get_current();
+
+	process_lock(cproc);
+
+	ret_val = process_get_pagedir(cproc, &pgdir);
+
+	if(!ret_val) {
+		ret_val = (int)pg_dir_sbrk(pgdir, increment);
+	}
+
+	process_unlock(cproc);
+
+	return(ret_val);
+}
+
 #if FEATURE(ELF)
 int sys_execelf(stack_frame_t *stk)
 {
@@ -366,6 +387,10 @@ int sys_posixcall(stack_frame_t *stk)
 		ret_val = sys_sleep((unsigned int)stk->ebx);
 		break;
 
+	case SYS_SBRK:
+		ret_val = sys_sbrk((ssize_t)stk->ebx);
+		break;
+
 	case SYS_EXECFVE:
 		ret_val = sys_execfve(stk);
 		break;
diff --git a/kernel/klibc/posixcall.S b/kernel/klibc/posixcall.S
index 0b455c2..f54608b 100644
--- a/kernel/klibc/posixcall.S
+++ b/kernel/klibc/posixcall.S
@@ -9,6 +9,8 @@
 
 	.global fork
 	.global execfve
+	.global brk
+	.global sbrk
 
 fork:
 	pushl	%ebx
@@ -31,4 +33,32 @@ execfve:
 	popl	%ebx
 	ret
 
+brk:
+	pushl	$0
+	call	sbrk
+
+	/*
+	 * The eax register contains the current sbrk, 8(%esp) the desired sbrk.
+	 * We have to pass the difference to sbrk() to increase or decrease it.
+	 */
+	movl	8(%esp), %edx
+	subl	%eax, %edx
+
+	/* sbrk(8(%esp) - sbrk(0)) */
+	movl	%edx, (%esp)
+	call	sbrk
+
+	addl	$4, %esp
+	ret
+
+sbrk:
+	pushl	%ebx
+
+	movl	$SYS_SBRK, %eax
+	movl	8(%esp), %ebx
+	int		$SYSCALL_POSIX
+
+	popl	%ebx
+	ret
+
 #endif /* FEATURE(POSIX) */