[Qemu-devel] [PATCH 2/9] linux-user/elfload: add FDPIC support

[Mike Frysinger <vapier@gentoo.org>]

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 elf.h                |   19 +++++++++++++
 linux-user/elfload.c |   71 ++++++++++++++++++++++++++++++++++++++++++++++++++
 linux-user/qemu.h    |    7 +++++
 3 files changed, 97 insertions(+), 0 deletions(-)

diff --git a/elf.h b/elf.h
index 7067c90..d2f24f4 100644
--- a/elf.h
+++ b/elf.h
@@ -1191,6 +1191,25 @@ typedef struct elf64_note {
   Elf64_Word n_type;	/* Content type */
 } Elf64_Nhdr;
 
+
+/* This data structure represents a PT_LOAD segment.  */
+struct elf32_fdpic_loadseg {
+  /* Core address to which the segment is mapped.  */
+  Elf32_Addr addr;
+  /* VMA recorded in the program header.  */
+  Elf32_Addr p_vaddr;
+  /* Size of this segment in memory.  */
+  Elf32_Word p_memsz;
+};
+struct elf32_fdpic_loadmap {
+  /* Protocol version number, must be zero.  */
+  Elf32_Half version;
+  /* Number of segments in this map.  */
+  Elf32_Half nsegs;
+  /* The actual memory map.  */
+  struct elf32_fdpic_loadseg segs[/*nsegs*/];
+};
+
 #ifdef ELF_CLASS
 #if ELF_CLASS == ELFCLASS32
 
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 33d776d..8c6d448 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1075,6 +1075,33 @@ static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot)
     }
 }
 
+#ifdef CONFIG_USE_FDPIC
+static abi_ulong loader_build_fdpic_loadmap(struct image_info *info, abi_ulong sp)
+{
+    uint16_t n;
+    struct elf32_fdpic_loadseg *loadsegs = info->loadsegs;
+
+    /* elf32_fdpic_loadseg */
+    n = info->nsegs;
+    while (n--) {
+        sp -= 12;
+        put_user_u32(loadsegs[n].addr, sp+0);
+        put_user_u32(loadsegs[n].p_vaddr, sp+4);
+        put_user_u32(loadsegs[n].p_memsz, sp+8);
+    }
+
+    /* elf32_fdpic_loadmap */
+    sp -= 4;
+    put_user_u16(0, sp+0); /* version */
+    put_user_u16(info->nsegs, sp+2); /* nsegs */
+
+    info->personality = PER_LINUX_FDPIC;
+    info->loadmap_addr = sp;
+
+    return sp;
+}
+#endif
+
 static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
                                    struct elfhdr *exec,
                                    struct image_info *info,
@@ -1087,6 +1114,21 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
     const int n = sizeof(elf_addr_t);
 
     sp = p;
+
+#ifdef CONFIG_USE_FDPIC
+    /* Needs to be before we load the env/argc/... */
+    if (elf_is_fdpic(exec)) {
+        /* Need 4 byte alignment for these structs */
+        sp &= ~3;
+        sp = loader_build_fdpic_loadmap(info, sp);
+        info->other_info = interp_info;
+        if (interp_info) {
+            interp_info->other_info = info;
+            sp = loader_build_fdpic_loadmap(interp_info, sp);
+        }
+    }
+#endif
+
     u_platform = 0;
     k_platform = ELF_PLATFORM;
     if (k_platform) {
@@ -1197,6 +1239,11 @@ static void load_elf_image(const char *image_name, int image_fd,
     }
     bswap_phdr(phdr, ehdr->e_phnum);
 
+#ifdef CONFIG_USE_FDPIC
+    info->nsegs = 0;
+    info->pt_dynamic_addr = 0;
+#endif
+
     /* Find the maximum size of the image and allocate an appropriate
        amount of memory to handle that.  */
     loaddr = -1, hiaddr = 0;
@@ -1210,6 +1257,9 @@ static void load_elf_image(const char *image_name, int image_fd,
             if (a > hiaddr) {
                 hiaddr = a;
             }
+#ifdef CONFIG_USE_FDPIC
+            ++info->nsegs;
+#endif
         }
     }
 
@@ -1290,6 +1340,27 @@ static void load_elf_image(const char *image_name, int image_fd,
     }
     load_bias = load_addr - loaddr;
 
+#ifdef CONFIG_USE_FDPIC
+    {
+        struct elf32_fdpic_loadseg *loadsegs = info->loadsegs =
+            qemu_malloc(sizeof(*loadsegs) * info->nsegs);
+
+        for (i = 0; i < ehdr->e_phnum; ++i) {
+            switch (phdr[i].p_type) {
+            case PT_DYNAMIC:
+                info->pt_dynamic_addr = phdr[i].p_vaddr + load_bias;
+                break;
+            case PT_LOAD:
+                loadsegs->addr = phdr[i].p_vaddr + load_bias;
+                loadsegs->p_vaddr = phdr[i].p_vaddr;
+                loadsegs->p_memsz = phdr[i].p_memsz;
+                ++loadsegs;
+                break;
+            }
+        }
+    }
+#endif
+
     info->load_bias = load_bias;
     info->load_addr = load_addr;
     info->entry = ehdr->e_entry + load_bias;
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 32de241..250814d 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -51,6 +51,13 @@ struct image_info {
         abi_ulong       arg_start;
         abi_ulong       arg_end;
 	int		personality;
+#ifdef CONFIG_USE_FDPIC
+        abi_ulong       loadmap_addr;
+        uint16_t        nsegs;
+        void           *loadsegs;
+        abi_ulong       pt_dynamic_addr;
+        struct image_info *other_info;
+#endif
 };
 
 #ifdef TARGET_I386
-- 
1.7.4