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[PATCH v7 12/14] linux-user: Use elf_et_dyn_base for ET_DYN with interpr
From: |
Richard Henderson |
Subject: |
[PATCH v7 12/14] linux-user: Use elf_et_dyn_base for ET_DYN with interpreter |
Date: |
Wed, 2 Aug 2023 18:53:00 -0700 |
Follow the lead of the linux kernel in fs/binfmt_elf.c,
in which an ET_DYN executable which uses an interpreter
(usually a PIE executable) is loaded away from where the
interpreter itself will be loaded.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
linux-user/elfload.c | 43 +++++++++++++++++++++++++++++++++++++++----
1 file changed, 39 insertions(+), 4 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 2aee2298ec..fef9a0bc8f 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -3021,7 +3021,7 @@ static void load_elf_image(const char *image_name, int
image_fd,
struct elfhdr *ehdr = (struct elfhdr *)bprm_buf;
struct elf_phdr *phdr;
abi_ulong load_addr, load_bias, loaddr, hiaddr, error;
- int i, retval, prot_exec;
+ int i, retval, prot_exec, load_map_flags;
Error *err = NULL;
/* First of all, some simple consistency checks */
@@ -3106,6 +3106,19 @@ static void load_elf_image(const char *image_name, int
image_fd,
}
}
+ load_addr = loaddr;
+
+ /*
+ * For ET_EXEC, load_addr is required. Use MAP_FIXED_NOREPLACE instead
+ * of MAP_FIXED on the off-chance that the guest address overlaps a
+ * host address. There should be no other conflict this early in the
+ * loading process.
+ */
+ if (ehdr->e_type == ET_EXEC) {
+ load_map_flags = MAP_FIXED_NOREPLACE;
+ } else {
+ load_map_flags = 0;
+ }
if (pinterp_name != NULL) {
/*
* This is the main executable.
@@ -3135,11 +3148,34 @@ static void load_elf_image(const char *image_name, int
image_fd,
*/
probe_guest_base(image_name, loaddr, hiaddr);
} else {
+ abi_ulong align;
+
/*
* The binary is dynamic, but we still need to
* select guest_base. In this case we pass a size.
*/
probe_guest_base(image_name, 0, hiaddr - loaddr);
+
+ /*
+ * Avoid collision with the loader by providing a different
+ * default load address.
+ */
+ load_addr = loaddr + elf_et_dyn_base;
+
+ /*
+ * TODO: Better support for mmap alignment is desirable.
+ * Without reserved_va we would prefer any host conflict be
+ * resolved by choosing a different address, therefore we
+ * don't want to use MAP_FIXED. But without that we cannot
+ * cannot guarantee alignment, only suggest it.
+ */
+ align = pow2ceil(info->alignment);
+ if (align) {
+ load_addr &= -align;
+ }
+ if (reserved_va) {
+ load_map_flags = MAP_FIXED_NOREPLACE;
+ }
}
}
@@ -3157,10 +3193,9 @@ static void load_elf_image(const char *image_name, int
image_fd,
* In both cases, we will overwrite pages in this range with mappings
* from the executable.
*/
- load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE,
+ load_addr = target_mmap(load_addr, (size_t)hiaddr - loaddr + 1, PROT_NONE,
MAP_PRIVATE | MAP_ANON | MAP_NORESERVE |
- (ehdr->e_type == ET_EXEC ? MAP_FIXED : 0),
- -1, 0);
+ load_map_flags, -1, 0);
if (load_addr == -1) {
goto exit_mmap;
}
--
2.34.1
- [PATCH v7 05/14] linux-user: Do nothing if too small brk is specified, (continued)
- [PATCH v7 05/14] linux-user: Do nothing if too small brk is specified, Richard Henderson, 2023/08/02
- [PATCH v7 04/14] linux-user: Use MAP_FIXED_NOREPLACE for do_brk(), Richard Henderson, 2023/08/02
- [PATCH v7 07/14] linux-user: Remove last_brk, Richard Henderson, 2023/08/02
- [PATCH v7 08/14] bsd-user: Remove last_brk, Richard Henderson, 2023/08/02
- [PATCH v7 09/14] linux-user: Adjust task_unmapped_base for reserved_va, Richard Henderson, 2023/08/02
- [PATCH v7 06/14] linux-user: Do not align brk with host page size, Richard Henderson, 2023/08/02
- [PATCH v7 10/14] linux-user: Define TASK_UNMAPPED_BASE in $guest/target_mman.h, Richard Henderson, 2023/08/02
- [PATCH v7 11/14] linux-user: Add ELF_ET_DYN_BASE, Richard Henderson, 2023/08/02
- [PATCH v7 13/14] linux-user: Adjust initial brk when interpreter is close to executable, Richard Henderson, 2023/08/02
- [PATCH v7 12/14] linux-user: Use elf_et_dyn_base for ET_DYN with interpreter,
Richard Henderson <=
- [PATCH v7 14/14] linux-user: Properly set image_info.brk in flatload, Richard Henderson, 2023/08/02
- Re: [PATCH v7 00/14] linux-user: brk fixes, Joel Stanley, 2023/08/03