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linux-user: Load vdso image if available

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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.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2021-06-17 09:03:19 -07:00
parent d0b6b79323
commit c40f621a19
1 changed files with 81 additions and 9 deletions
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90
linux-user/elfload.c
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@ -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 */
@ -2471,7 +2484,8 @@ 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;
@ -2559,10 +2573,15 @@ 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
@ -2644,6 +2663,9 @@ 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
@ -3521,6 +3543,52 @@ 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;
@ -3726,7 +3794,7 @@ 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;
@ -3807,10 +3875,13 @@ 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);
@ -3822,8 +3893,9 @@ 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.