The vdso image will be pre-processed into a C data array, with
a simple list of relocations to perform, and identifying the
location of signal trampolines.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
linux-user/elfload.c | 90 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 81 insertions(+), 9 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index ed276edb3c..9c97d14b7e 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -33,6 +33,19 @@
#undef ELF_ARCH
#endif
+#ifndef TARGET_ARCH_HAS_SIGTRAMP_PAGE
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+#endif
+
+typedef struct {
+ const uint8_t *image;
+ const uint32_t *relocs;
+ unsigned image_size;
+ unsigned reloc_count;
+ unsigned sigreturn_ofs;
+ unsigned rt_sigreturn_ofs;
+} VdsoImageInfo;
+
#define ELF_OSABI ELFOSABI_SYSV
/* from personality.h */
@@ -2436,7 +2449,8 @@ static abi_ulong loader_build_fdpic_loadmap(struct
image_info *info, abi_ulong s
static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
struct elfhdr *exec,
struct image_info *info,
- struct image_info *interp_info)
+ struct image_info *interp_info,
+ struct image_info *vdso_info)
{
abi_ulong sp;
abi_ulong u_argc, u_argv, u_envp, u_auxv;
@@ -2524,10 +2538,15 @@ static abi_ulong create_elf_tables(abi_ulong p, int
argc, int envc,
}
size = (DLINFO_ITEMS + 1) * 2;
- if (k_base_platform)
+ if (k_base_platform) {
size += 2;
- if (k_platform)
+ }
+ if (k_platform) {
size += 2;
+ }
+ if (vdso_info) {
+ size += 2;
+ }
#ifdef DLINFO_ARCH_ITEMS
size += DLINFO_ARCH_ITEMS * 2;
#endif
@@ -2609,6 +2628,9 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc,
int envc,
if (u_platform) {
NEW_AUX_ENT(AT_PLATFORM, u_platform);
}
+ if (vdso_info) {
+ NEW_AUX_ENT(AT_SYSINFO_EHDR, vdso_info->load_addr);
+ }
NEW_AUX_ENT (AT_NULL, 0);
#undef NEW_AUX_ENT
@@ -3486,6 +3508,52 @@ static void load_elf_interp(const char *filename, struct
image_info *info,
load_elf_image(filename, &src, info, &ehdr, NULL);
}
+#ifdef VDSO_HEADER
+#include VDSO_HEADER
+#define vdso_image_info() &vdso_image_info
+#else
+#define vdso_image_info() NULL
+#endif
+
+static void load_elf_vdso(struct image_info *info, const VdsoImageInfo *vdso)
+{
+ ImageSource src;
+ struct elfhdr ehdr;
+ abi_ulong load_bias, load_addr;
+
+ src.fd = -1;
+ src.cache = vdso->image;
+ src.cache_size = vdso->image_size;
+
+ load_elf_image("<internal-vdso>", &src, info, &ehdr, NULL);
+ load_addr = info->load_addr;
+ load_bias = info->load_bias;
+
+ /*
+ * We need to relocate the VDSO image. The one built into the kernel
+ * is built for a fixed address. The one built for QEMU is not, since
+ * that requires close control of the guest address space.
+ * We pre-processed the image to locate all of the addresses that need
+ * to be updated.
+ */
+ for (unsigned i = 0, n = vdso->reloc_count; i < n; i++) {
+ abi_ulong *addr = g2h_untagged(load_addr + vdso->relocs[i]);
+ *addr = tswapal(tswapal(*addr) + load_bias);
+ }
+
+ /* Install signal trampolines, if present. */
+ if (vdso->sigreturn_ofs) {
+ default_sigreturn = load_addr + vdso->sigreturn_ofs;
+ }
+ if (vdso->rt_sigreturn_ofs) {
+ default_rt_sigreturn = load_addr + vdso->rt_sigreturn_ofs;
+ }
+
+ /* Remove write from VDSO segment. */
+ target_mprotect(info->start_data, info->end_data - info->start_data,
+ PROT_READ | PROT_EXEC);
+}
+
static int symfind(const void *s0, const void *s1)
{
struct elf_sym *sym = (struct elf_sym *)s1;
@@ -3691,7 +3759,7 @@ int load_elf_binary(struct linux_binprm *bprm, struct
image_info *info)
* and let elf_load_image do any swapping that may be required.
*/
struct elfhdr ehdr;
- struct image_info interp_info;
+ struct image_info interp_info, vdso_info;
char *elf_interpreter = NULL;
char *scratch;
@@ -3772,10 +3840,13 @@ int load_elf_binary(struct linux_binprm *bprm, struct
image_info *info)
}
/*
- * TODO: load a vdso, which would also contain the signal trampolines.
- * Otherwise, allocate a private page to hold them.
+ * Load a vdso if available, which will amongst other things contain the
+ * signal trampolines. Otherwise, allocate a separate page for them.
*/
- if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) {
+ const VdsoImageInfo *vdso = vdso_image_info();
+ if (vdso) {
+ load_elf_vdso(&vdso_info, vdso);
+ } else if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) {
abi_long tramp_page = target_mmap(0, TARGET_PAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON, -1, 0);
@@ -3787,8 +3858,9 @@ int load_elf_binary(struct linux_binprm *bprm, struct
image_info *info)
target_mprotect(tramp_page, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC);
}
- bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &ehdr,
- info, (elf_interpreter ? &interp_info : NULL));
+ bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &ehdr, info,
+ elf_interpreter ? &interp_info : NULL,
+ vdso ? &vdso_info : NULL);
info->start_stack = bprm->p;
/* If we have an interpreter, set that as the program's entry point.
--
2.34.1
