113 lines
4.1 KiB
Diff
113 lines
4.1 KiB
Diff
https://github.com/qemu/qemu/commit/6fd5944980f4ccee728ce34bdaffc117db50b34d
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diff -uNr qemu-4.1.1/linux-user/elfload.c qemu-4.1.1.mod/linux-user/elfload.c
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--- qemu-4.1.1/linux-user/elfload.c 2020-02-13 22:19:06.939675451 +0200
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+++ qemu-4.1.1.mod/linux-user/elfload.c 2020-02-13 22:22:26.853718260 +0200
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@@ -11,6 +11,7 @@
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#include "disas/disas.h"
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#include "qemu/path.h"
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#include "qemu/guest-random.h"
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+#include "qemu/units.h"
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#ifdef _ARCH_PPC64
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#undef ARCH_DLINFO
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@@ -2340,24 +2341,51 @@
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}
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}
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- load_addr = loaddr;
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- if (ehdr->e_type == ET_DYN) {
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- /* The image indicates that it can be loaded anywhere. Find a
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- location that can hold the memory space required. If the
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- image is pre-linked, LOADDR will be non-zero. Since we do
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- not supply MAP_FIXED here we'll use that address if and
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- only if it remains available. */
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- load_addr = target_mmap(loaddr, hiaddr - loaddr, PROT_NONE,
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- MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
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- -1, 0);
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- if (load_addr == -1) {
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- goto exit_perror;
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- }
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- } else if (pinterp_name != NULL) {
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- /* This is the main executable. Make sure that the low
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- address does not conflict with MMAP_MIN_ADDR or the
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- QEMU application itself. */
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- probe_guest_base(image_name, loaddr, hiaddr);
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+ if (pinterp_name != NULL) {
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+ /*
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+ * This is the main executable.
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+ *
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+ * Reserve extra space for brk.
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+ * We hold on to this space while placing the interpreter
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+ * and the stack, lest they be placed immediately after
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+ * the data segment and block allocation from the brk.
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+ *
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+ * 16MB is chosen as "large enough" without being so large
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+ * as to allow the result to not fit with a 32-bit guest on
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+ * a 32-bit host.
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+ */
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+ info->reserve_brk = 16 * MiB;
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+ hiaddr += info->reserve_brk;
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+
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+ if (ehdr->e_type == ET_EXEC) {
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+ /*
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+ * Make sure that the low address does not conflict with
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+ * MMAP_MIN_ADDR or the QEMU application itself.
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+ */
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+ probe_guest_base(image_name, loaddr, hiaddr);
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+ }
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+ }
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+
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+ /*
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+ * Reserve address space for all of this.
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+ *
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+ * In the case of ET_EXEC, we supply MAP_FIXED so that we get
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+ * exactly the address range that is required.
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+ *
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+ * Otherwise this is ET_DYN, and we are searching for a location
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+ * that can hold the memory space required. If the image is
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+ * pre-linked, LOADDR will be non-zero, and the kernel should
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+ * honor that address if it happens to be free.
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+ *
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+ * In both cases, we will overwrite pages in this range with mappings
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+ * from the executable.
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+ */
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+ load_addr = target_mmap(loaddr, hiaddr - loaddr, PROT_NONE,
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+ MAP_PRIVATE | MAP_ANON | MAP_NORESERVE |
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+ (ehdr->e_type == ET_EXEC ? MAP_FIXED : 0),
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+ -1, 0);
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+ if (load_addr == -1) {
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+ goto exit_perror;
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}
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load_bias = load_addr - loaddr;
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@@ -2834,6 +2862,17 @@
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bprm->core_dump = &elf_core_dump;
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#endif
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+ /*
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+ * If we reserved extra space for brk, release it now.
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+ * The implementation of do_brk in syscalls.c expects to be able
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+ * to mmap pages in this space.
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+ */
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+ if (info->reserve_brk) {
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+ abi_ulong start_brk = HOST_PAGE_ALIGN(info->brk);
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+ abi_ulong end_brk = HOST_PAGE_ALIGN(info->brk + info->reserve_brk);
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+ target_munmap(start_brk, end_brk - start_brk);
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+ }
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+
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return 0;
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}
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diff -uNr qemu-4.1.1/linux-user/qemu.h qemu-4.1.1.mod/linux-user/qemu.h
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--- qemu-4.1.1/linux-user/qemu.h 2019-11-14 20:06:20.000000000 +0200
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+++ qemu-4.1.1.mod/linux-user/qemu.h 2020-02-13 22:22:26.854718265 +0200
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@@ -36,6 +36,7 @@
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abi_ulong end_data;
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abi_ulong start_brk;
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abi_ulong brk;
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+ abi_ulong reserve_brk;
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abi_ulong start_mmap;
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abi_ulong start_stack;
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abi_ulong stack_limit;
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