Abandon MIPS convention for indicating syscall errors in register a3

12 files changed, 154 insertions, 121 deletions

diff --git a/pk/elf.c b/pk/elf.c
index 607d7ea..79ee756 100644
--- a/pk/elf.c
+++ b/pk/elf.c
@@ -10,13 +10,12 @@
 
 void load_elf(const char* fn, elf_info* info)
 {
-  sysret_t ret = file_open(fn, O_RDONLY, 0);
-  file_t* file = (file_t*)ret.result;
-  if (ret.result == -1)
+  file_t* file = file_open(fn, O_RDONLY, 0);
+  if (IS_ERR_VALUE(file))
     goto fail;
 
   Elf64_Ehdr eh64;
-  ssize_t ehdr_size = file_pread(file, &eh64, sizeof(eh64), 0).result;
+  ssize_t ehdr_size = file_pread(file, &eh64, sizeof(eh64), 0);
   if (ehdr_size < (ssize_t)sizeof(eh64) ||
       !(eh64.e_ident[0] == '\177' && eh64.e_ident[1] == 'E' &&
         eh64.e_ident[2] == 'L'    && eh64.e_ident[3] == 'F'))
@@ -28,7 +27,7 @@ void load_elf(const char* fn, elf_info* info)
     if (info->phdr_top - phdr_size < info->stack_bottom) \
       goto fail; \
     info->phdr = info->phdr_top - phdr_size; \
-    ssize_t ret = file_pread(file, (void*)info->phdr, phdr_size, eh->e_phoff).result; \
+    ssize_t ret = file_pread(file, (void*)info->phdr, phdr_size, eh->e_phoff); \
     if (ret < (ssize_t)phdr_size) goto fail; \
     info->entry = eh->e_entry; \
     info->phnum = eh->e_phnum; \
diff --git a/pk/encoding.h b/pk/encoding.h
index 711ef7b..4ee6e68 100644
--- a/pk/encoding.h
+++ b/pk/encoding.h
@@ -26,19 +26,6 @@
 #define IMPL_SPIKE  1
 #define IMPL_ROCKET 2
 
-#define CAUSE_MISALIGNED_FETCH 0
-#define CAUSE_FAULT_FETCH 1
-#define CAUSE_ILLEGAL_INSTRUCTION 2
-#define CAUSE_PRIVILEGED_INSTRUCTION 3
-#define CAUSE_FP_DISABLED 4
-#define CAUSE_SYSCALL 6
-#define CAUSE_BREAKPOINT 7
-#define CAUSE_MISALIGNED_LOAD 8
-#define CAUSE_MISALIGNED_STORE 9
-#define CAUSE_FAULT_LOAD 10
-#define CAUSE_FAULT_STORE 11
-#define CAUSE_ACCELERATOR_DISABLED 12
-
 // page table entry (PTE) fields
 #define PTE_V    0x001 // Entry is a page Table descriptor
 #define PTE_T    0x002 // Entry is a page Table, not a terminal node
@@ -438,6 +425,18 @@
 #define CSR_CYCLE 0xc00
 #define CSR_TIME 0xc01
 #define CSR_INSTRET 0xc02
+#define CAUSE_MISALIGNED_FETCH 0x0
+#define CAUSE_FAULT_FETCH 0x1
+#define CAUSE_ILLEGAL_INSTRUCTION 0x2
+#define CAUSE_PRIVILEGED_INSTRUCTION 0x3
+#define CAUSE_FP_DISABLED 0x4
+#define CAUSE_SYSCALL 0x6
+#define CAUSE_BREAKPOINT 0x7
+#define CAUSE_MISALIGNED_LOAD 0x8
+#define CAUSE_MISALIGNED_STORE 0x9
+#define CAUSE_FAULT_LOAD 0xa
+#define CAUSE_FAULT_STORE 0xb
+#define CAUSE_ACCELERATOR_DISABLED 0xc
 #endif
 #ifdef DECLARE_INSN
 DECLARE_INSN(fmv_s_x, MATCH_FMV_S_X, MASK_FMV_S_X)
@@ -624,3 +623,31 @@ DECLARE_CSR(cycle, CSR_CYCLE)
 DECLARE_CSR(time, CSR_TIME)
 DECLARE_CSR(instret, CSR_INSTRET)
 #endif
+#ifdef DECLARE_CAUSE
+DECLARE_CAUSE("fflags", CAUSE_FFLAGS)
+DECLARE_CAUSE("frm", CAUSE_FRM)
+DECLARE_CAUSE("fcsr", CAUSE_FCSR)
+DECLARE_CAUSE("sup0", CAUSE_SUP0)
+DECLARE_CAUSE("sup1", CAUSE_SUP1)
+DECLARE_CAUSE("epc", CAUSE_EPC)
+DECLARE_CAUSE("badvaddr", CAUSE_BADVADDR)
+DECLARE_CAUSE("ptbr", CAUSE_PTBR)
+DECLARE_CAUSE("asid", CAUSE_ASID)
+DECLARE_CAUSE("count", CAUSE_COUNT)
+DECLARE_CAUSE("compare", CAUSE_COMPARE)
+DECLARE_CAUSE("evec", CAUSE_EVEC)
+DECLARE_CAUSE("cause", CAUSE_CAUSE)
+DECLARE_CAUSE("status", CAUSE_STATUS)
+DECLARE_CAUSE("hartid", CAUSE_HARTID)
+DECLARE_CAUSE("impl", CAUSE_IMPL)
+DECLARE_CAUSE("fatc", CAUSE_FATC)
+DECLARE_CAUSE("send_ipi", CAUSE_SEND_IPI)
+DECLARE_CAUSE("clear_ipi", CAUSE_CLEAR_IPI)
+DECLARE_CAUSE("stats", CAUSE_STATS)
+DECLARE_CAUSE("reset", CAUSE_RESET)
+DECLARE_CAUSE("tohost", CAUSE_TOHOST)
+DECLARE_CAUSE("fromhost", CAUSE_FROMHOST)
+DECLARE_CAUSE("cycle", CAUSE_CYCLE)
+DECLARE_CAUSE("time", CAUSE_TIME)
+DECLARE_CAUSE("instret", CAUSE_INSTRET)
+#endif
diff --git a/pk/file.c b/pk/file.c
index ca6d1e5..6c3ecda 100644
--- a/pk/file.c
+++ b/pk/file.c
@@ -83,23 +83,24 @@ file_t* file_get(int fd)
   return f;
 }
 
-sysret_t file_open(const char* fn, int flags, int mode)
+file_t* file_open(const char* fn, int flags, int mode)
 {
   file_t* f = file_get_free();
-  if(!f)
-    return (sysret_t){-1,ENOMEM};
+  if (f == NULL)
+    return ERR_PTR(-ENOMEM);
 
   size_t fn_size = strlen(fn)+1;
-  sysret_t ret = frontend_syscall(SYS_open, (long)fn, fn_size, flags, mode);
-  if(ret.result != -1)
+  long ret = frontend_syscall(SYS_open, (long)fn, fn_size, flags, mode);
+  if (ret >= 0)
   {
-    f->kfd = ret.result;
-    ret.result = (long)f;
+    f->kfd = ret;
+    return f;
   }
   else
+  {
     file_decref(f);
-
-  return ret;
+    return ERR_PTR(ret);
+  }
 }
 
 int fd_close(int fd)
@@ -115,37 +116,37 @@ int fd_close(int fd)
   return 0;
 }
 
-sysret_t file_read(file_t* f, void* buf, size_t size)
+ssize_t file_read(file_t* f, void* buf, size_t size)
 {
   populate_mapping(buf, size, PROT_WRITE);
   return frontend_syscall(SYS_read, f->kfd, (uintptr_t)buf, size, 0);
 }
 
-sysret_t file_pread(file_t* f, void* buf, size_t size, off_t offset)
+ssize_t file_pread(file_t* f, void* buf, size_t size, off_t offset)
 {
   populate_mapping(buf, size, PROT_WRITE);
   return frontend_syscall(SYS_pread, f->kfd, (uintptr_t)buf, size, offset);
 }
 
-sysret_t file_write(file_t* f, const void* buf, size_t size)
+ssize_t file_write(file_t* f, const void* buf, size_t size)
 {
   populate_mapping(buf, size, PROT_READ);
   return frontend_syscall(SYS_write, f->kfd, (uintptr_t)buf, size, 0);
 }
 
-sysret_t file_pwrite(file_t* f, const void* buf, size_t size, off_t offset)
+ssize_t file_pwrite(file_t* f, const void* buf, size_t size, off_t offset)
 {
   populate_mapping(buf, size, PROT_READ);
   return frontend_syscall(SYS_pwrite, f->kfd, (uintptr_t)buf, size, offset);
 }
 
-sysret_t file_stat(file_t* f, struct stat* s)
+int file_stat(file_t* f, struct stat* s)
 {
   populate_mapping(s, sizeof(*s), PROT_WRITE);
   return frontend_syscall(SYS_fstat, f->kfd, (uintptr_t)s, 0, 0);
 }
 
-sysret_t file_lseek(file_t* f, size_t ptr, int dir)
+ssize_t file_lseek(file_t* f, size_t ptr, int dir)
 {
   return frontend_syscall(SYS_lseek, f->kfd, ptr, dir, 0);
 }
diff --git a/pk/file.h b/pk/file.h
index 42f47fc..88338e6 100644
--- a/pk/file.h
+++ b/pk/file.h
@@ -16,17 +16,17 @@ typedef struct file
 extern file_t *stdin, *stdout, *stderr;
 
 file_t* file_get(int fd);
-sysret_t file_open(const char* fn, int flags, int mode);
+file_t* file_open(const char* fn, int flags, int mode);
 void file_decref(file_t*);
 void file_incref(file_t*);
 int file_dup(file_t*);
 
-sysret_t file_pwrite(file_t* f, const void* buf, size_t n, off_t off);
-sysret_t file_pread(file_t* f, void* buf, size_t n, off_t off);
-sysret_t file_write(file_t* f, const void* buf, size_t n);
-sysret_t file_read(file_t* f, void* buf, size_t n);
-sysret_t file_stat(file_t* f, struct stat* s);
-sysret_t file_lseek(file_t* f, size_t ptr, int dir);
+ssize_t file_pwrite(file_t* f, const void* buf, size_t n, off_t off);
+ssize_t file_pread(file_t* f, void* buf, size_t n, off_t off);
+ssize_t file_write(file_t* f, const void* buf, size_t n);
+ssize_t file_read(file_t* f, void* buf, size_t n);
+ssize_t file_lseek(file_t* f, size_t ptr, int dir);
+int file_stat(file_t* f, struct stat* s);
 int fd_close(int fd);
 
 void file_init();
diff --git a/pk/frontend.c b/pk/frontend.c
index 3452b23..77d71a6 100644
--- a/pk/frontend.c
+++ b/pk/frontend.c
@@ -5,7 +5,7 @@
 #include "frontend.h"
 #include <stdint.h>
 
-sysret_t frontend_syscall(long n, long a0, long a1, long a2, long a3)
+long frontend_syscall(long n, long a0, long a1, long a2, long a3)
 {
   static volatile uint64_t magic_mem[8];
 
@@ -25,7 +25,7 @@ sysret_t frontend_syscall(long n, long a0, long a1, long a2, long a3)
 
   mb();
 
-  sysret_t ret = {magic_mem[0],magic_mem[1]};
+  long ret = magic_mem[0];
 
   spinlock_unlock(&lock);
   return ret;
diff --git a/pk/frontend.h b/pk/frontend.h
index a3bc4de..9610234 100644
--- a/pk/frontend.h
+++ b/pk/frontend.h
@@ -3,8 +3,6 @@
 #ifndef _RISCV_FRONTEND_H
 #define _RISCV_FRONTEND_H
 
-#include <machine/syscall.h>
-
-sysret_t frontend_syscall(long n, long a0, long a1, long a2, long a3);
+long frontend_syscall(long n, long a0, long a1, long a2, long a3);
 
 #endif
diff --git a/pk/handlers.c b/pk/handlers.c
index 2c50ae6..94a4127 100644
--- a/pk/handlers.c
+++ b/pk/handlers.c
@@ -109,12 +109,8 @@ void handle_fault_store(trapframe_t* tf)
 
 static void handle_syscall(trapframe_t* tf)
 {
-  sysret_t ret = syscall(tf->gpr[18], tf->gpr[19], tf->gpr[20], tf->gpr[21],
-                         tf->gpr[22], tf->gpr[23], tf->gpr[16]);
-
-  tf->gpr[16] = ret.result;
-  tf->gpr[21] = ret.err;
-
+  tf->gpr[16] = syscall(tf->gpr[18], tf->gpr[19], tf->gpr[20], tf->gpr[21],
+                        tf->gpr[22], tf->gpr[23], tf->gpr[16]);
   tf->epc += 4;
 }
 
diff --git a/pk/init.c b/pk/init.c
index 848da65..d6974f7 100644
--- a/pk/init.c
+++ b/pk/init.c
@@ -54,8 +54,8 @@ static void user_init()
   size_t stack_top = current.stack_top;
   struct args* args = (struct args*)(stack_top - argc_argv_size);
   populate_mapping(args, argc_argv_size, PROT_WRITE);
-  sysret_t r = frontend_syscall(SYS_getmainvars, (long)args, argc_argv_size, 0, 0);
-  kassert(r.result == 0);
+  long r = frontend_syscall(SYS_getmainvars, (long)args, argc_argv_size, 0, 0);
+  kassert(r == 0);
 
   // argv[0] is the proxy kernel itself.  skip it and any flags.
   unsigned a0 = 1;
diff --git a/pk/syscall.c b/pk/syscall.c
index 044cc78..6d58be0 100644
--- a/pk/syscall.c
+++ b/pk/syscall.c
@@ -8,7 +8,7 @@
 #include <string.h>
 #include <errno.h>
 
-typedef sysret_t (*syscall_t)(long, long, long, long, long, long, long);
+typedef long (*syscall_t)(long, long, long, long, long, long, long);
 
 #define long_bytes (4 + 4*current.elf64)
 #define get_long(base, i) ({ long res; \
@@ -30,9 +30,9 @@ void sys_exit(int code)
   while (1);
 }
 
-sysret_t sys_read(int fd, char* buf, size_t n)
+ssize_t sys_read(int fd, char* buf, size_t n)
 {
-  sysret_t r = {-1,EBADF};
+  ssize_t r = -EBADF;
   file_t* f = file_get(fd);
 
   if (f)
@@ -44,9 +44,9 @@ sysret_t sys_read(int fd, char* buf, size_t n)
   return r;
 }
 
-sysret_t sys_write(int fd, const char* buf, size_t n)
+ssize_t sys_write(int fd, const char* buf, size_t n)
 {
-  sysret_t r = {-1,EBADF};
+  ssize_t r = -EBADF;
   file_t* f = file_get(fd);
 
   if (f)
@@ -58,27 +58,30 @@ sysret_t sys_write(int fd, const char* buf, size_t n)
   return r;
 }
 
-sysret_t sys_open(const char* name, int flags, int mode)
+int sys_open(const char* name, int flags, int mode)
 {
-  sysret_t ret = file_open(name, flags, mode);
-  if(ret.result == -1)
-    return ret;
+  file_t* file = file_open(name, flags, mode);
+  if (IS_ERR_VALUE(file))
+    return PTR_ERR(file);
 
-  if((ret.result = file_dup((file_t*)ret.result)) == -1)
-    ret.err = ENOMEM;
+  int fd = file_dup(file);
+  if (fd < 0)
+    return -ENOMEM;
 
-  return ret;
+  return fd;
 }
 
-sysret_t sys_close(int fd)
+int sys_close(int fd)
 {
   int ret = fd_close(fd);
-  return (sysret_t){ret, ret & EBADF};
+  if (ret < 0)
+    return -EBADF;
+  return ret;
 }
 
-sysret_t sys_fstat(int fd, void* st)
+int sys_fstat(int fd, void* st)
 {
-  sysret_t r = {-1,EBADF};
+  int r = -EBADF;
   file_t* f = file_get(fd);
 
   if (f)
@@ -90,9 +93,9 @@ sysret_t sys_fstat(int fd, void* st)
   return r;
 }
 
-sysret_t sys_lseek(int fd, size_t ptr, int dir)
+ssize_t sys_lseek(int fd, size_t ptr, int dir)
 {
-  sysret_t r = {-1,EBADF};
+  ssize_t r = -EBADF;
   file_t* f = file_get(fd);
 
   if (f)
@@ -104,21 +107,21 @@ sysret_t sys_lseek(int fd, size_t ptr, int dir)
   return r;
 }
 
-sysret_t sys_stat(const char* name, void* st)
+long sys_stat(const char* name, void* st)
 {
   size_t name_size = strlen(name)+1;
   populate_mapping(st, sizeof(struct stat), PROT_WRITE);
   return frontend_syscall(SYS_stat, (uintptr_t)name, name_size, (uintptr_t)st, 0);
 }
 
-sysret_t sys_lstat(const char* name, void* st)
+long sys_lstat(const char* name, void* st)
 {
   size_t name_size = strlen(name)+1;
   populate_mapping(st, sizeof(struct stat), PROT_WRITE);
   return frontend_syscall(SYS_lstat, (uintptr_t)name, name_size, (uintptr_t)st, 0);
 }
 
-sysret_t sys_link(const char* old_name, const char* new_name)
+long sys_link(const char* old_name, const char* new_name)
 {
   size_t old_size = strlen(old_name)+1;
   size_t new_size = strlen(new_name)+1;
@@ -126,18 +129,18 @@ sysret_t sys_link(const char* old_name, const char* new_name)
                                     (uintptr_t)new_name, new_size);
 }
 
-sysret_t sys_unlink(const char* name, size_t len)
+long sys_unlink(const char* name, size_t len)
 {
   size_t name_size = strlen(name)+1;
   return frontend_syscall(SYS_unlink, (uintptr_t)name, name_size, 0, 0);
 }
 
-sysret_t sys_brk(size_t pos)
+size_t sys_brk(size_t pos)
 {
   return do_brk(pos);
 }
 
-sysret_t sys_uname(void* buf)
+int sys_uname(void* buf)
 {
   const int sz = 65;
   strcpy(buf + 0*sz, "Proxy Kernel");
@@ -146,30 +149,30 @@ sysret_t sys_uname(void* buf)
   strcpy(buf + 3*sz, "");
   strcpy(buf + 4*sz, "");
   strcpy(buf + 5*sz, "");
-  return (sysret_t){0,0};
+  return 0;
 }
 
-sysret_t sys_getuid()
+int sys_getuid()
 {
-  return (sysret_t){0,0};
+  return 0;
 }
 
-sysret_t sys_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset)
+uintptr_t sys_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset)
 {
   return do_mmap(addr, length, prot, flags, fd, offset);
 }
 
-sysret_t sys_munmap(uintptr_t addr, size_t length)
+int sys_munmap(uintptr_t addr, size_t length)
 {
   return do_munmap(addr, length);
 }
 
-sysret_t sys_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags)
+uintptr_t sys_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags)
 {
   return do_mremap(addr, old_size, new_size, flags);
 }
 
-sysret_t sys_rt_sigaction(int sig, const void* act, void* oact, size_t sssz)
+int sys_rt_sigaction(int sig, const void* act, void* oact, size_t sssz)
 {
   if (oact)
   {
@@ -178,21 +181,21 @@ sysret_t sys_rt_sigaction(int sig, const void* act, void* oact, size_t sssz)
     memset(oact, 0, sz);
   }
 
-  return (sysret_t){0, 0};
+  return 0;
 }
 
-sysret_t sys_time(void* loc)
+long sys_time(void* loc)
 {
-  uintptr_t t = rdcycle();
+  uintptr_t t = rdcycle() / CLOCK_FREQ;
   if (loc)
   {
     populate_mapping(loc, long_bytes, PROT_WRITE);
-    put_long(loc, 0, t / CLOCK_FREQ);
+    put_long(loc, 0, t);
   }
-  return (sysret_t){t, 0};
+  return t;
 }
 
-sysret_t sys_times(void* restrict loc)
+int sys_times(void* restrict loc)
 {
   populate_mapping(loc, 4*long_bytes, PROT_WRITE);
 
@@ -203,10 +206,10 @@ sysret_t sys_times(void* restrict loc)
   put_long(loc, 2, 0);
   put_long(loc, 3, 0);
   
-  return (sysret_t){0, 0};
+  return 0;
 }
 
-sysret_t sys_gettimeofday(long* loc)
+int sys_gettimeofday(long* loc)
 {
   populate_mapping(loc, 2*long_bytes, PROT_WRITE);
 
@@ -214,25 +217,25 @@ sysret_t sys_gettimeofday(long* loc)
   put_long(loc, 0, t/CLOCK_FREQ);
   put_long(loc, 1, (t % CLOCK_FREQ) / (CLOCK_FREQ / 1000000));
   
-  return (sysret_t){0, 0};
+  return 0;
 }
 
-sysret_t sys_writev(int fd, const void* iov, int cnt)
+ssize_t sys_writev(int fd, const void* iov, int cnt)
 {
   populate_mapping(iov, cnt*2*long_bytes, PROT_READ);
 
   ssize_t ret = 0;
   for (int i = 0; i < cnt; i++)
   {
-    sysret_t r = sys_write(fd, (void*)get_long(iov, 2*i), get_long(iov, 2*i+1));
-    if (r.result < 0)
+    ssize_t r = sys_write(fd, (void*)get_long(iov, 2*i), get_long(iov, 2*i+1));
+    if (r < 0)
       return r;
-    ret += r.result;
+    ret += r;
   }
-  return (sysret_t){ret, 0};
+  return ret;
 }
 
-sysret_t syscall(long a0, long a1, long a2, long a3, long a4, long a5, long n)
+long syscall(long a0, long a1, long a2, long a3, long a4, long a5, long n)
 {
   const static void* syscall_table[] = {
     [SYS_exit] = sys_exit,
@@ -266,6 +269,6 @@ sysret_t syscall(long a0, long a1, long a2, long a3, long a4, long a5, long n)
   if(n >= ARRAY_SIZE(syscall_table) || !syscall_table[n])
     panic("bad syscall #%ld!",n);
 
-  sysret_t r = ((syscall_t)syscall_table[n])(a0, a1, a2, a3, a4, a5, n);
+  long r = ((syscall_t)syscall_table[n])(a0, a1, a2, a3, a4, a5, n);
   return r;
 }
diff --git a/pk/syscall.h b/pk/syscall.h
index f759e83..fcb3423 100644
--- a/pk/syscall.h
+++ b/pk/syscall.h
@@ -1,6 +1,15 @@
 // See LICENSE for license details.
 
+#ifndef _PK_SYSCALL_H
+#define _PK_SYSCALL_H
+
 #include <machine/syscall.h>
 
+#define IS_ERR_VALUE(x) ((unsigned long)(x) >= (unsigned long)-4096)
+#define ERR_PTR(x) ((void*)(long)(x))
+#define PTR_ERR(x) ((long)(x))
+
 void sys_exit(int code) __attribute__((noreturn));
-sysret_t syscall(long a0, long a1, long a2, long a3, long a4, long a5, long n);
+long syscall(long a0, long a1, long a2, long a3, long a4, long a5, long n);
+
+#endif
diff --git a/pk/vm.c b/pk/vm.c
index 6f02930..6a3dd3b 100644
--- a/pk/vm.c
+++ b/pk/vm.c
@@ -177,7 +177,7 @@ static int __handle_page_fault(uintptr_t vaddr, int prot)
     if (v->file)
     {
       size_t flen = MIN(RISCV_PGSIZE, v->length - (vaddr - v->addr));
-      kassert(flen == file_pread(v->file, (void*)vaddr, flen, vaddr - v->addr + v->offset).result);
+      kassert(flen == file_pread(v->file, (void*)vaddr, flen, vaddr - v->addr + v->offset));
       if (flen < RISCV_PGSIZE)
         memset((void*)vaddr + flen, 0, RISCV_PGSIZE - flen);
     }
@@ -259,27 +259,27 @@ fail_vmr:
   return (uintptr_t)-1;
 }
 
-sysret_t do_munmap(uintptr_t addr, size_t length)
+int do_munmap(uintptr_t addr, size_t length)
 {
   if ((addr & (RISCV_PGSIZE-1)) || addr < current.user_min ||
       addr + length > current.stack_top || addr + length < addr)
-    return (sysret_t){-1, EINVAL};
+    return -EINVAL;
 
   spinlock_lock(&vm_lock);
     __do_munmap(addr, length);
   spinlock_unlock(&vm_lock);
 
-  return (sysret_t){0, 0};
+  return 0;
 }
 
-sysret_t do_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset)
+uintptr_t do_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset)
 {
   if (!(flags & MAP_PRIVATE) || length == 0 || (offset & (RISCV_PGSIZE-1)))
-    return (sysret_t){-1, EINVAL};
+    return -EINVAL;
 
   file_t* f = NULL;
   if (!(flags & MAP_ANONYMOUS) && (f = file_get(fd)) == NULL)
-    return (sysret_t){-1, EBADF};
+    return -EBADF;
 
   spinlock_lock(&vm_lock);
     addr = __do_mmap(addr, length, prot, flags, f, offset);
@@ -288,12 +288,12 @@ sysret_t do_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off
   spinlock_unlock(&vm_lock);
 
   if (f) file_decref(f);
-  return (sysret_t){addr, 0};
+  return addr;
 }
 
-size_t __do_brk(size_t addr)
+uintptr_t __do_brk(size_t addr)
 {
-  size_t newbrk = addr;
+  uintptr_t newbrk = addr;
   if (addr < current.brk_min)
     newbrk = current.brk_min;
   else if (addr > current.brk_max)
@@ -302,7 +302,7 @@ size_t __do_brk(size_t addr)
   if (current.brk == 0)
     current.brk = ROUNDUP(current.brk_min, RISCV_PGSIZE);
 
-  size_t newbrk_page = ROUNDUP(newbrk, RISCV_PGSIZE);
+  uintptr_t newbrk_page = ROUNDUP(newbrk, RISCV_PGSIZE);
   if (current.brk > newbrk_page)
     __do_munmap(newbrk_page, current.brk - newbrk_page);
   else if (current.brk < newbrk_page)
@@ -312,21 +312,21 @@ size_t __do_brk(size_t addr)
   return newbrk;
 }
 
-sysret_t do_brk(size_t addr)
+uintptr_t do_brk(size_t addr)
 {
   spinlock_lock(&vm_lock);
     addr = __do_brk(addr);
   spinlock_unlock(&vm_lock);
   
-  return (sysret_t){addr, 0};
+  return addr;
 }
 
-sysret_t do_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags)
+uintptr_t do_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags)
 {
   uintptr_t res = -1;
   if (((addr | old_size | new_size) & (RISCV_PGSIZE-1)) ||
       (flags & MREMAP_FIXED))
-    return (sysret_t){-1, EINVAL};
+    return -EINVAL;
 
   spinlock_lock(&vm_lock);
     for (size_t i = 0; i < MAX_VMR; i++)
@@ -346,7 +346,7 @@ sysret_t do_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags)
     }
   spinlock_unlock(&vm_lock);
  
-  return (sysret_t){res, 0};
+  return res;
 }
 
 static void __map_kernel_range(uintptr_t paddr, size_t len, int prot)
diff --git a/pk/vm.h b/pk/vm.h
index 8f5e55f..cdd4f77 100644
--- a/pk/vm.h
+++ b/pk/vm.h
@@ -21,9 +21,9 @@ void vm_init();
 int handle_page_fault(uintptr_t vaddr, int prot);
 void populate_mapping(const void* start, size_t size, int prot);
 uintptr_t __do_mmap(uintptr_t addr, size_t length, int prot, int flags, file_t* file, off_t offset);
-sysret_t do_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset);
-sysret_t do_munmap(uintptr_t addr, size_t length);
-sysret_t do_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags);
-sysret_t do_brk(uintptr_t addr);
+uintptr_t do_mmap(uintptr_t addr, size_t length, int prot, int flags, int fd, off_t offset);
+int do_munmap(uintptr_t addr, size_t length);
+uintptr_t do_mremap(uintptr_t addr, size_t old_size, size_t new_size, int flags);
+uintptr_t do_brk(uintptr_t addr);
 
 #endif