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[PATCH 09/12] linux-user: Load vdso image if available
From: |
Richard Henderson |
Subject: |
[PATCH 09/12] linux-user: Load vdso image if available |
Date: |
Fri, 18 Jun 2021 20:43:26 -0700 |
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.henderson@linaro.org>
---
linux-user/elfload.c | 75 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 67 insertions(+), 8 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 8a3a7ae3ac..a6ad454617 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1966,7 +1966,8 @@ 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;
@@ -2038,8 +2039,12 @@ static abi_ulong create_elf_tables(abi_ulong p, int
argc, int envc,
}
size = (DLINFO_ITEMS + 1) * 2;
- if (k_platform)
+ if (k_platform) {
size += 2;
+ }
+ if (vdso_info) {
+ size += 4;
+ }
#ifdef DLINFO_ARCH_ITEMS
size += DLINFO_ARCH_ITEMS * 2;
#endif
@@ -2116,6 +2121,10 @@ 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, vdso_info->entry);
+ NEW_AUX_ENT(AT_SYSINFO_EHDR, vdso_info->load_addr);
+ }
NEW_AUX_ENT (AT_NULL, 0);
#undef NEW_AUX_ENT
@@ -2942,6 +2951,53 @@ static void load_elf_interp(const char *filename, struct
image_info *info,
load_elf_image(filename, &src, info, &ehdr, NULL);
}
+#ifndef HAVE_VDSO
+#define HAVE_VDSO 0
+static uint8_t vdso_image[] = { };
+static uint32_t vdso_relocs[] = { };
+#define vdso_sigreturn 0
+#define vdso_rt_sigreturn 0
+#endif
+
+static void load_elf_vdso(struct image_info *info)
+{
+ ImageSource src;
+ struct elfhdr ehdr;
+ abi_ulong load_bias, load_addr;
+
+ src.fd = -1;
+ src.cache = vdso_image;
+ src.cache_size = sizeof(vdso_image);
+
+ 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 (size_t i = 0, n = ARRAY_SIZE(vdso_relocs); 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) {
+ default_sigreturn = load_addr + vdso_sigreturn;
+ }
+ if (vdso_rt_sigreturn) {
+ default_rt_sigreturn = load_addr + vdso_rt_sigreturn;
+ }
+
+ /* Mark the VDSO writable segment read-only. */
+ target_mprotect(info->start_data, info->end_data - info->start_data,
+ PROT_READ);
+}
+
static int symfind(const void *s0, const void *s1)
{
target_ulong addr = *(target_ulong *)s0;
@@ -3146,7 +3202,7 @@ 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;
@@ -3216,10 +3272,12 @@ 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) {
+ if (HAVE_VDSO) {
+ load_elf_vdso(&vdso_info);
+ } else if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) {
abi_ulong tramp_page = target_mmap(0, TARGET_PAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON, -1, 0);
@@ -3227,8 +3285,9 @@ 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,
+ HAVE_VDSO ? &vdso_info : NULL);
info->start_stack = bprm->p;
/* If we have an interpreter, set that as the program's entry point.
--
2.25.1
- Re: [PATCH 01/12] linux-user: Fix style problems in linuxload.c, (continued)
- [PATCH 02/12] linux-user: Introduce imgsrc_read, imgsrc_read_alloc, Richard Henderson, 2021/06/18
- [PATCH 03/12] linux-user: Tidy loader_exec, Richard Henderson, 2021/06/18
- [PATCH 04/12] linux-user: Do not clobber bprm_buf swapping ehdr, Richard Henderson, 2021/06/18
- [PATCH 06/12] linux-user: Use ImageSource in load_symbols, Richard Henderson, 2021/06/18
- [PATCH 05/12] linux-user: Use ImageSource in load_elf_image, Richard Henderson, 2021/06/18
- [PATCH 12/12] linux-user/hppa: Add vdso and use it for rt_sigreturn, Richard Henderson, 2021/06/18
- [PATCH 07/12] linux-user: Replace bprm->fd with bprm->src.fd, Richard Henderson, 2021/06/18
- [PATCH 09/12] linux-user: Load vdso image if available,
Richard Henderson <=
- [PATCH 11/12] linux-user/x86_64: Add vdso, Richard Henderson, 2021/06/18
- [PATCH 08/12] linux-user: Introduce imgsrc_mmap, Richard Henderson, 2021/06/18
- [PATCH 10/12] linux-user: Add gen-vdso tool, Richard Henderson, 2021/06/18
- Re: [PATCH 00/12] linux-user: Load a vdso for x86_64 and hppa, no-reply, 2021/06/19