semihosting: Split out semihost_sys_read

Split out the non-ARM specific portions of SYS_READ to a
reusable function.  This handles all GuestFD.  Isolate the
curious ARM-specific return value processing to a new
callback, common_semi_rw_cb.

Note that gdb_do_syscall %x reads target_ulong, not int.

Reviewed-by: Luc Michel <lmichel@kalray.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 105 insertions, 65 deletions

diff --git a/semihosting/arm-compat-semi.c b/semihosting/arm-compat-semi.c
index 0cb3db2..8da31d8 100644
--- a/semihosting/arm-compat-semi.c
+++ b/semihosting/arm-compat-semi.c
@@ -231,7 +231,6 @@ static void common_semi_cb(CPUState *cs, target_ulong ret, target_ulong err)
         target_ulong reg0 = common_semi_arg(cs, 0);
         switch (reg0) {
         case TARGET_SYS_WRITE:
-        case TARGET_SYS_READ:
             ret = common_semi_syscall_len - ret;
             break;
         case TARGET_SYS_SEEK:
@@ -245,6 +244,25 @@ static void common_semi_cb(CPUState *cs, target_ulong ret, target_ulong err)
 }
 
 /*
+ * SYS_READ and SYS_WRITE always return the number of bytes not read/written.
+ * There is no error condition, other than returning the original length.
+ */
+static void common_semi_rw_cb(CPUState *cs, target_ulong ret, target_ulong err)
+{
+    /* Recover the original length from the third argument. */
+    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
+    target_ulong args = common_semi_arg(cs, 1);
+    target_ulong arg2;
+    GET_ARG(2);
+
+    if (err) {
+ do_fault:
+        ret = 0; /* error: no bytes transmitted */
+    }
+    common_semi_set_ret(cs, arg2 - ret);
+}
+
+/*
  * Return an address in target memory of 64 bytes where the remote
  * gdb should write its stat struct. (The format of this structure
  * is defined by GDB's remote protocol and is not target-specific.)
@@ -278,8 +296,6 @@ common_semi_flen_cb(CPUState *cs, target_ulong ret, target_ulong err)
  */
 typedef void sys_writefn(CPUState *cs, GuestFD *gf,
                          target_ulong buf, uint32_t len);
-typedef void sys_readfn(CPUState *cs, GuestFD *gf,
-                        target_ulong buf, uint32_t len);
 typedef void sys_isattyfn(CPUState *cs, GuestFD *gf);
 typedef void sys_seekfn(CPUState *cs, GuestFD *gf, target_ulong offset);
 typedef void sys_flenfn(CPUState *cs, GuestFD *gf);
@@ -302,26 +318,6 @@ static void host_writefn(CPUState *cs, GuestFD *gf,
     common_semi_cb(cs, len - ret, 0);
 }
 
-static void host_readfn(CPUState *cs, GuestFD *gf,
-                        target_ulong buf, uint32_t len)
-{
-    CPUArchState *env = cs->env_ptr;
-    uint32_t ret = 0;
-    char *s = lock_user(VERIFY_WRITE, buf, len, 0);
-    (void) env; /* Used in arm softmmu lock_user implicitly */
-    if (s) {
-        do {
-            ret = read(gf->hostfd, s, len);
-        } while (ret == -1 && errno == EINTR);
-        unlock_user(s, buf, len);
-        if (ret == (uint32_t)-1) {
-            ret = 0;
-        }
-    }
-    /* Return bytes not read, on error as well. */
-    common_semi_cb(cs, len - ret, 0);
-}
-
 static void host_isattyfn(CPUState *cs, GuestFD *gf)
 {
     common_semi_cb(cs, isatty(gf->hostfd), 0);
@@ -351,13 +347,6 @@ static void gdb_writefn(CPUState *cs, GuestFD *gf,
     gdb_do_syscall(common_semi_cb, "write,%x,%x,%x", gf->hostfd, buf, len);
 }
 
-static void gdb_readfn(CPUState *cs, GuestFD *gf,
-                       target_ulong buf, uint32_t len)
-{
-    common_semi_syscall_len = len;
-    gdb_do_syscall(common_semi_cb, "read,%x,%x,%x", gf->hostfd, buf, len);
-}
-
 static void gdb_isattyfn(CPUState *cs, GuestFD *gf)
 {
     gdb_do_syscall(common_semi_cb, "isatty,%x", gf->hostfd);
@@ -398,30 +387,6 @@ static void staticfile_writefn(CPUState *cs, GuestFD *gf,
     common_semi_cb(cs, -1, EBADF);
 }
 
-static void staticfile_readfn(CPUState *cs, GuestFD *gf,
-                              target_ulong buf, uint32_t len)
-{
-    CPUArchState *env = cs->env_ptr;
-    uint32_t i = 0;
-    char *s;
-
-    (void) env; /* Used in arm softmmu lock_user implicitly */
-    s = lock_user(VERIFY_WRITE, buf, len, 0);
-    if (s) {
-        for (i = 0; i < len; i++) {
-            if (gf->staticfile.off >= gf->staticfile.len) {
-                break;
-            }
-            s[i] = gf->staticfile.data[gf->staticfile.off];
-            gf->staticfile.off++;
-        }
-        unlock_user(s, buf, len);
-    }
-
-    /* Return number of bytes not read */
-    common_semi_cb(cs, len - i, 0);
-}
-
 static void staticfile_isattyfn(CPUState *cs, GuestFD *gf)
 {
     common_semi_cb(cs, 0, 0);
@@ -440,7 +405,6 @@ static void staticfile_flenfn(CPUState *cs, GuestFD *gf)
 
 typedef struct GuestFDFunctions {
     sys_writefn *writefn;
-    sys_readfn *readfn;
     sys_isattyfn *isattyfn;
     sys_seekfn *seekfn;
     sys_flenfn *flenfn;
@@ -449,21 +413,18 @@ typedef struct GuestFDFunctions {
 static const GuestFDFunctions guestfd_fns[] = {
     [GuestFDHost] = {
         .writefn = host_writefn,
-        .readfn = host_readfn,
         .isattyfn = host_isattyfn,
         .seekfn = host_seekfn,
         .flenfn = host_flenfn,
     },
     [GuestFDGDB] = {
         .writefn = gdb_writefn,
-        .readfn = gdb_readfn,
         .isattyfn = gdb_isattyfn,
         .seekfn = gdb_seekfn,
         .flenfn = gdb_flenfn,
     },
     [GuestFDStatic] = {
         .writefn = staticfile_writefn,
-        .readfn = staticfile_readfn,
         .isattyfn = staticfile_isattyfn,
         .seekfn = staticfile_seekfn,
         .flenfn = staticfile_flenfn,
@@ -583,13 +544,7 @@ void do_common_semihosting(CPUState *cs)
         GET_ARG(0);
         GET_ARG(1);
         GET_ARG(2);
-        len = arg2;
-
-        gf = get_guestfd(arg0);
-        if (!gf) {
-            goto do_badf;
-        }
-        guestfd_fns[gf->type].readfn(cs, gf, arg1, len);
+        semihost_sys_read(cs, common_semi_rw_cb, arg0, arg1, arg2);
         break;
 
     case TARGET_SYS_READC:
diff --git a/semihosting/syscalls.c b/semihosting/syscalls.c
index 3648b9d..d42a190 100644
--- a/semihosting/syscalls.c
+++ b/semihosting/syscalls.c
@@ -100,6 +100,13 @@ static void gdb_close(CPUState *cs, gdb_syscall_complete_cb complete,
     gdb_do_syscall(complete, "close,%x", (target_ulong)gf->hostfd);
 }
 
+static void gdb_read(CPUState *cs, gdb_syscall_complete_cb complete,
+                     GuestFD *gf, target_ulong buf, target_ulong len)
+{
+    gdb_do_syscall(complete, "read,%x,%x,%x",
+                   (target_ulong)gf->hostfd, buf, len);
+}
+
 /*
  * Host semihosting syscall implementations.
  */
@@ -163,6 +170,54 @@ static void host_close(CPUState *cs, gdb_syscall_complete_cb complete,
     }
 }
 
+static void host_read(CPUState *cs, gdb_syscall_complete_cb complete,
+                      GuestFD *gf, target_ulong buf, target_ulong len)
+{
+    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
+    void *ptr = lock_user(VERIFY_WRITE, buf, len, 0);
+    ssize_t ret;
+
+    if (!ptr) {
+        complete(cs, -1, EFAULT);
+        return;
+    }
+    do {
+        ret = read(gf->hostfd, ptr, len);
+    } while (ret == -1 && errno == EINTR);
+    if (ret == -1) {
+        complete(cs, -1, errno);
+        unlock_user(ptr, buf, 0);
+    } else {
+        complete(cs, ret, 0);
+        unlock_user(ptr, buf, ret);
+    }
+}
+
+/*
+ * Static file semihosting syscall implementations.
+ */
+
+static void staticfile_read(CPUState *cs, gdb_syscall_complete_cb complete,
+                            GuestFD *gf, target_ulong buf, target_ulong len)
+{
+    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
+    target_ulong rest = gf->staticfile.len - gf->staticfile.off;
+    void *ptr;
+
+    if (len > rest) {
+        len = rest;
+    }
+    ptr = lock_user(VERIFY_WRITE, buf, len, 0);
+    if (!ptr) {
+        complete(cs, -1, EFAULT);
+        return;
+    }
+    memcpy(ptr, gf->staticfile.data + gf->staticfile.off, len);
+    gf->staticfile.off += len;
+    complete(cs, len, 0);
+    unlock_user(ptr, buf, len);
+}
+
 /*
  * Syscall entry points.
  */
@@ -201,3 +256,33 @@ void semihost_sys_close(CPUState *cs, gdb_syscall_complete_cb complete, int fd)
     }
     dealloc_guestfd(fd);
 }
+
+void semihost_sys_read_gf(CPUState *cs, gdb_syscall_complete_cb complete,
+                          GuestFD *gf, target_ulong buf, target_ulong len)
+{
+    switch (gf->type) {
+    case GuestFDGDB:
+        gdb_read(cs, complete, gf, buf, len);
+        break;
+    case GuestFDHost:
+        host_read(cs, complete, gf, buf, len);
+        break;
+    case GuestFDStatic:
+        staticfile_read(cs, complete, gf, buf, len);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+void semihost_sys_read(CPUState *cs, gdb_syscall_complete_cb complete,
+                       int fd, target_ulong buf, target_ulong len)
+{
+    GuestFD *gf = get_guestfd(fd);
+
+    if (gf) {
+        semihost_sys_read_gf(cs, complete, gf, buf, len);
+    } else {
+        complete(cs, -1, EBADF);
+    }
+}