[PATCH v2 03/36] linux-user: Introduce imgsrc_read, imgsrc_read_alloc

[Richard Henderson <richard.henderson@linaro.org>]

Introduced and initialized, but not yet really used.
These will tidy the current tests vs BPRM_BUF_SIZE.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/qemu.h      | 50 ++++++++++++++++++++++++++++++++++--------
 linux-user/linuxload.c | 46 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 9 deletions(-)

diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 9e5e2aa499..f4cdfb16b3 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -168,6 +168,37 @@ extern unsigned long mmap_min_addr;
 
 /* ??? See if we can avoid exposing so much of the loader internals.  */
 
+typedef struct {
+    const void *cache;
+    unsigned int cache_size;
+    int fd;
+} ImageSource;
+
+/**
+ * imgsrc_read: Read from ImageSource
+ * @dst: destination for read
+ * @offset: offset within file for read
+ * @len: size of the read
+ * @img: ImageSource to read from
+ * @errp: Error details.
+ *
+ * Read into @dst, using the cache when possible.
+ */
+bool imgsrc_read(void *dst, off_t offset, size_t len,
+                 const ImageSource *img, Error **errp);
+
+/**
+ * imgsrc_read_alloc: Read from ImageSource
+ * @offset: offset within file for read
+ * @size: size of the read
+ * @img: ImageSource to read from
+ * @errp: Error details.
+ *
+ * Read into newly allocated memory, using the cache when possible.
+ */
+void *imgsrc_read_alloc(off_t offset, size_t len,
+                        const ImageSource *img, Error **errp);
+
 /* Read a good amount of data initially, to hopefully get all the
    program headers loaded.  */
 #define BPRM_BUF_SIZE  1024
@@ -177,15 +208,16 @@ extern unsigned long mmap_min_addr;
  * used when loading binaries.
  */
 struct linux_binprm {
-        char buf[BPRM_BUF_SIZE] __attribute__((aligned));
-        abi_ulong p;
-        int fd;
-        int e_uid, e_gid;
-        int argc, envc;
-        char **argv;
-        char **envp;
-        char * filename;        /* Name of binary */
-        int (*core_dump)(int, const CPUArchState *); /* coredump routine */
+    char buf[BPRM_BUF_SIZE] __attribute__((aligned));
+    ImageSource src;
+    abi_ulong p;
+    int fd;
+    int e_uid, e_gid;
+    int argc, envc;
+    char **argv;
+    char **envp;
+    char *filename;  /* Name of binary */
+    int (*core_dump)(int, const CPUArchState *); /* coredump routine */
 };
 
 typedef struct IOCTLEntry IOCTLEntry;
diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
index 9d4eb5e94b..3b0bafc490 100644
--- a/linux-user/linuxload.c
+++ b/linux-user/linuxload.c
@@ -2,6 +2,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu.h"
+#include "qapi/error.h"
 
 #define NGROUPS 32
 
@@ -74,6 +75,10 @@ static int prepare_binprm(struct linux_binprm *bprm)
         /* Make sure the rest of the loader won't read garbage.  */
         memset(bprm->buf + retval, 0, BPRM_BUF_SIZE - retval);
     }
+
+    bprm->src.cache = bprm->buf;
+    bprm->src.cache_size = retval;
+
     return retval;
 }
 
@@ -129,6 +134,7 @@ int loader_exec(int fdexec, const char *filename, char **argv, char **envp,
     int retval;
 
     bprm->fd = fdexec;
+    bprm->src.fd = fdexec;
     bprm->filename = (char *)filename;
     bprm->argc = count(argv);
     bprm->argv = argv;
@@ -163,3 +169,43 @@ int loader_exec(int fdexec, const char *filename, char **argv, char **envp,
 
     return retval;
 }
+
+bool imgsrc_read(void *dst, off_t offset, size_t len,
+                 const ImageSource *img, Error **errp)
+{
+    ssize_t ret;
+
+    if (offset + len <= img->cache_size) {
+        memcpy(dst, img->cache + offset, len);
+        return true;
+    }
+
+    if (img->fd < 0) {
+        error_setg(errp, "read past end of buffer");
+        return false;
+    }
+
+    ret = pread(img->fd, dst, len, offset);
+    if (ret == len) {
+        return true;
+    }
+    if (ret < 0) {
+        error_setg_errno(errp, errno, "Error reading file header");
+    } else {
+        error_setg(errp, "Incomplete read of file header");
+    }
+    return false;
+}
+
+void *imgsrc_read_alloc(off_t offset, size_t len,
+                        const ImageSource *img, Error **errp)
+{
+    void *alloc = g_malloc(len);
+    bool ok = imgsrc_read(alloc, offset, len, img, errp);
+
+    if (!ok) {
+        g_free(alloc);
+        alloc = NULL;
+    }
+    return alloc;
+}
-- 
2.25.1