linux-user: Use ImageSource in load_symbols

Aside from the section headers, we're unlikely to hit the
ImageSource cache on guest executables.  But the interface
for imgsrc_read_* is better.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -2201,7 +2201,8 @@ static inline void bswap_mips_abiflags(Mips_elf_abiflags_v0 *abiflags) { }
 #ifdef USE_ELF_CORE_DUMP
 static int elf_core_dump(int, const CPUArchState *);
 #endif /* USE_ELF_CORE_DUMP */
-static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias);
+static void load_symbols(struct elfhdr *hdr, const ImageSource *src,
+                         abi_ulong load_bias);
 
 /* Verify the portions of EHDR within E_IDENT for the target.
    This can be performed before bswapping the entire header.  */
@@ -3473,7 +3474,7 @@ static void load_elf_image(const char *image_name, const ImageSource *src,
     }
 
     if (qemu_log_enabled()) {
-        load_symbols(ehdr, src->fd, load_bias);
+        load_symbols(ehdr, src, load_bias);
     }
 
     debuginfo_report_elf(image_name, src->fd, load_bias);
@@ -3564,19 +3565,20 @@ static int symcmp(const void *s0, const void *s1)
 }
 
 /* Best attempt to load symbols from this ELF object. */
-static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
+static void load_symbols(struct elfhdr *hdr, const ImageSource *src,
+                         abi_ulong load_bias)
 {
     int i, shnum, nsyms, sym_idx = 0, str_idx = 0;
-    uint64_t segsz;
+    g_autofree struct elf_shdr *shdr = NULL;
-    struct elf_shdr *shdr;
     char *strings = NULL;
-    struct syminfo *s = NULL;
+    struct elf_sym *syms = NULL;
-    struct elf_sym *new_syms, *syms = NULL;
+    struct elf_sym *new_syms;
+    uint64_t segsz;
 
     shnum = hdr->e_shnum;
-    i = shnum * sizeof(struct elf_shdr);
+    shdr = imgsrc_read_alloc(hdr->e_shoff, shnum * sizeof(struct elf_shdr),
-    shdr = (struct elf_shdr *)alloca(i);
+                             src, NULL);
-    if (pread(fd, shdr, i, hdr->e_shoff) != i) {
+    if (shdr == NULL) {
         return;
     }
 
@@ -3594,31 +3596,33 @@ static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
 
  found:
     /* Now know where the strtab and symtab are.  Snarf them.  */
-    s = g_try_new(struct syminfo, 1);
-    if (!s) {
-        goto give_up;
-    }
 
     segsz = shdr[str_idx].sh_size;
-    s->disas_strtab = strings = g_try_malloc(segsz);
+    strings = g_try_malloc(segsz);
-    if (!strings ||
+    if (!strings) {
-        pread(fd, strings, segsz, shdr[str_idx].sh_offset) != segsz) {
+        goto give_up;
+    }
+    if (!imgsrc_read(strings, shdr[str_idx].sh_offset, segsz, src, NULL)) {
         goto give_up;
     }
 
     segsz = shdr[sym_idx].sh_size;
-    syms = g_try_malloc(segsz);
-    if (!syms || pread(fd, syms, segsz, shdr[sym_idx].sh_offset) != segsz) {
-        goto give_up;
-    }
-
     if (segsz / sizeof(struct elf_sym) > INT_MAX) {
-        /* Implausibly large symbol table: give up rather than ploughing
+        /*
-         * on with the number of symbols calculation overflowing
+         * Implausibly large symbol table: give up rather than ploughing
+         * on with the number of symbols calculation overflowing.
          */
         goto give_up;
     }
     nsyms = segsz / sizeof(struct elf_sym);
+    syms = g_try_malloc(segsz);
+    if (!syms) {
+        goto give_up;
+    }
+    if (!imgsrc_read(syms, shdr[sym_idx].sh_offset, segsz, src, NULL)) {
+        goto give_up;
+    }
+
     for (i = 0; i < nsyms; ) {
         bswap_sym(syms + i);
         /* Throw away entries which we do not need.  */
@@ -3643,10 +3647,12 @@ static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
         goto give_up;
     }
 
-    /* Attempt to free the storage associated with the local symbols
+    /*
-       that we threw away.  Whether or not this has any effect on the
+     * Attempt to free the storage associated with the local symbols
-       memory allocation depends on the malloc implementation and how
+     * that we threw away.  Whether or not this has any effect on the
-       many symbols we managed to discard.  */
+     * memory allocation depends on the malloc implementation and how
+     * many symbols we managed to discard.
+     */
     new_syms = g_try_renew(struct elf_sym, syms, nsyms);
     if (new_syms == NULL) {
         goto give_up;
@@ -3655,6 +3661,10 @@ static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
 
     qsort(syms, nsyms, sizeof(*syms), symcmp);
 
+    {
+        struct syminfo *s = g_new(struct syminfo, 1);
+
+        s->disas_strtab = strings;
         s->disas_num_syms = nsyms;
 #if ELF_CLASS == ELFCLASS32
         s->disas_symtab.elf32 = syms;
@@ -3664,11 +3674,10 @@ static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
         s->lookup_symbol = lookup_symbolxx;
         s->next = syminfos;
         syminfos = s;
-
+    }
     return;
 
  give_up:
-    g_free(s);
     g_free(strings);
     g_free(syms);
 }