Merge tag 'pull-lu-20230808' of https://gitlab.com/rth7680/qemu into staging

linux-user: Adjust guest image layout vs reserved_va
linux-user: Do not adjust image mapping for host page size
linux-user: Adjust initial brk when interpreter is close to executable
util/selfmap: Rewrite using qemu/interval-tree.h
linux-user: Rewrite probe_guest_base

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# gpg: Signature made Tue 08 Aug 2023 02:07:42 PM PDT
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [ultimate]

* tag 'pull-lu-20230808' of https://gitlab.com/rth7680/qemu:
  linux-user: Rewrite non-fixed probe_guest_base
  linux-user: Rewrite fixed probe_guest_base
  linux-user: Consolidate guest bounds check in probe_guest_base
  linux-user: Remove duplicate CPU_LOG_PAGE from probe_guest_base
  util/selfmap: Rewrite using qemu/interval-tree.h
  linux-user: Use zero_bss for PT_LOAD with no file contents too
  linux-user: Do not adjust zero_bss for host page size
  linux-user: Do not adjust image mapping for host page size
  linux-user: Adjust initial brk when interpreter is close to executable
  linux-user: Use elf_et_dyn_base for ET_DYN with interpreter
  linux-user: Use MAP_FIXED_NOREPLACE for initial image mmap
  linux-user: Define ELF_ET_DYN_BASE in $guest/target_mman.h
  linux-user: Define TASK_UNMAPPED_BASE in $guest/target_mman.h
  linux-user: Adjust task_unmapped_base for reserved_va

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

26 files changed, 687 insertions, 386 deletions

diff --git a/linux-user/aarch64/target_mman.h b/linux-user/aarch64/target_mman.h
index f721295..69ec5d5 100644
--- a/linux-user/aarch64/target_mman.h
+++ b/linux-user/aarch64/target_mman.h
@@ -4,6 +4,19 @@
 #define TARGET_PROT_BTI         0x10
 #define TARGET_PROT_MTE         0x20
 
+/*
+ * arch/arm64/include/asm/processor.h:
+ *
+ * TASK_UNMAPPED_BASE     DEFAULT_MAP_WINDOW / 4
+ * DEFAULT_MAP_WINDOW     DEFAULT_MAP_WINDOW_64
+ * DEFAULT_MAP_WINDOW_64  UL(1) << VA_BITS_MIN
+ * VA_BITS_MIN            48 (unless explicitly configured smaller)
+ */
+#define TASK_UNMAPPED_BASE      (1ull << (48 - 2))
+
+/* arch/arm64/include/asm/elf.h */
+#define ELF_ET_DYN_BASE         TARGET_PAGE_ALIGN((1ull << 48) / 3 * 2)
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/alpha/target_mman.h b/linux-user/alpha/target_mman.h
index 6bb03e7..8edfe2b 100644
--- a/linux-user/alpha/target_mman.h
+++ b/linux-user/alpha/target_mman.h
@@ -20,6 +20,17 @@
 #define TARGET_MS_SYNC 2
 #define TARGET_MS_INVALIDATE 4
 
+/*
+ * arch/alpha/include/asm/processor.h:
+ *
+ * TASK_UNMAPPED_BASE           TASK_SIZE / 2
+ * TASK_SIZE                    0x40000000000UL
+ */
+#define TASK_UNMAPPED_BASE      0x20000000000ull
+
+/* arch/alpha/include/asm/elf.h */
+#define ELF_ET_DYN_BASE         (TASK_UNMAPPED_BASE + 0x1000000)
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/arm/target_mman.h b/linux-user/arm/target_mman.h
index e7ba607..51005da 100644
--- a/linux-user/arm/target_mman.h
+++ b/linux-user/arm/target_mman.h
@@ -1 +1,12 @@
+/*
+ * arch/arm/include/asm/memory.h
+ * TASK_UNMAPPED_BASE        ALIGN(TASK_SIZE / 3, SZ_16M)
+ * TASK_SIZE                 CONFIG_PAGE_OFFSET
+ * CONFIG_PAGE_OFFSET        0xC0000000 (default in Kconfig)
+ */
+#define TASK_UNMAPPED_BASE   0x40000000
+
+/* arch/arm/include/asm/elf.h */
+#define ELF_ET_DYN_BASE      0x00400000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/cris/target_mman.h b/linux-user/cris/target_mman.h
index e7ba607..9ace8ac 100644
--- a/linux-user/cris/target_mman.h
+++ b/linux-user/cris/target_mman.h
@@ -1 +1,13 @@
+/*
+ * arch/cris/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE      (PAGE_ALIGN(TASK_SIZE / 3))
+ *
+ * arch/cris/include/arch-v32/arch/processor.h
+ * TASK_SIZE               0xb0000000
+ */
+#define TASK_UNMAPPED_BASE TARGET_PAGE_ALIGN(0xb0000000 / 3)
+
+/* arch/cris/include/uapi/asm/elf.h */
+#define ELF_ET_DYN_BASE    (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 36e4026..ac03beb 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1960,15 +1960,6 @@ struct exec
 #define ZMAGIC 0413
 #define QMAGIC 0314
 
-/* Necessary parameters */
-#define TARGET_ELF_EXEC_PAGESIZE \
-        (((eppnt->p_align & ~qemu_host_page_mask) != 0) ? \
-         TARGET_PAGE_SIZE : MAX(qemu_host_page_size, TARGET_PAGE_SIZE))
-#define TARGET_ELF_PAGELENGTH(_v) ROUND_UP((_v), TARGET_ELF_EXEC_PAGESIZE)
-#define TARGET_ELF_PAGESTART(_v) ((_v) & \
-                                 ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE-1))
-#define TARGET_ELF_PAGEOFFSET(_v) ((_v) & (TARGET_ELF_EXEC_PAGESIZE-1))
-
 #define DLINFO_ITEMS 16
 
 static inline void memcpy_fromfs(void * to, const void * from, unsigned long n)
@@ -2220,47 +2211,37 @@ static abi_ulong setup_arg_pages(struct linux_binprm *bprm,
     }
 }
 
-/* Map and zero the bss.  We need to explicitly zero any fractional pages
-   after the data section (i.e. bss).  */
-static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot)
+/**
+ * zero_bss:
+ *
+ * Map and zero the bss.  We need to explicitly zero any fractional pages
+ * after the data section (i.e. bss).  Return false on mapping failure.
+ */
+static bool zero_bss(abi_ulong start_bss, abi_ulong end_bss, int prot)
 {
-    uintptr_t host_start, host_map_start, host_end;
-
-    last_bss = TARGET_PAGE_ALIGN(last_bss);
-
-    /* ??? There is confusion between qemu_real_host_page_size and
-       qemu_host_page_size here and elsewhere in target_mmap, which
-       may lead to the end of the data section mapping from the file
-       not being mapped.  At least there was an explicit test and
-       comment for that here, suggesting that "the file size must
-       be known".  The comment probably pre-dates the introduction
-       of the fstat system call in target_mmap which does in fact
-       find out the size.  What isn't clear is if the workaround
-       here is still actually needed.  For now, continue with it,
-       but merge it with the "normal" mmap that would allocate the bss.  */
-
-    host_start = (uintptr_t) g2h_untagged(elf_bss);
-    host_end = (uintptr_t) g2h_untagged(last_bss);
-    host_map_start = REAL_HOST_PAGE_ALIGN(host_start);
-
-    if (host_map_start < host_end) {
-        void *p = mmap((void *)host_map_start, host_end - host_map_start,
-                       prot, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-        if (p == MAP_FAILED) {
-            perror("cannot mmap brk");
-            exit(-1);
-        }
-    }
+    abi_ulong align_bss;
 
-    /* Ensure that the bss page(s) are valid */
-    if ((page_get_flags(last_bss-1) & prot) != prot) {
-        page_set_flags(elf_bss & TARGET_PAGE_MASK, last_bss - 1,
-                       prot | PAGE_VALID);
-    }
+    align_bss = TARGET_PAGE_ALIGN(start_bss);
+    end_bss = TARGET_PAGE_ALIGN(end_bss);
 
-    if (host_start < host_map_start) {
-        memset((void *)host_start, 0, host_map_start - host_start);
+    if (start_bss < align_bss) {
+        int flags = page_get_flags(start_bss);
+
+        if (!(flags & PAGE_VALID)) {
+            /* Map the start of the bss. */
+            align_bss -= TARGET_PAGE_SIZE;
+        } else if (flags & PAGE_WRITE) {
+            /* The page is already mapped writable. */
+            memset(g2h_untagged(start_bss), 0, align_bss - start_bss);
+        } else {
+            /* Read-only zeros? */
+            g_assert_not_reached();
+        }
     }
+
+    return align_bss >= end_bss ||
+           target_mmap(align_bss, end_bss - align_bss, prot,
+                       MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) != -1;
 }
 
 #if defined(TARGET_ARM)
@@ -2523,308 +2504,322 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
 #endif
 #endif
 
-static void pgb_fail_in_use(const char *image_name)
+/**
+ * pgb_try_mmap:
+ * @addr: host start address
+ * @addr_last: host last address
+ * @keep: do not unmap the probe region
+ *
+ * Return 1 if [@addr, @addr_last] is not mapped in the host,
+ * return 0 if it is not available to map, and -1 on mmap error.
+ * If @keep, the region is left mapped on success, otherwise unmapped.
+ */
+static int pgb_try_mmap(uintptr_t addr, uintptr_t addr_last, bool keep)
 {
-    error_report("%s: requires virtual address space that is in use "
-                 "(omit the -B option or choose a different value)",
-                 image_name);
-    exit(EXIT_FAILURE);
+    size_t size = addr_last - addr + 1;
+    void *p = mmap((void *)addr, size, PROT_NONE,
+                   MAP_ANONYMOUS | MAP_PRIVATE |
+                   MAP_NORESERVE | MAP_FIXED_NOREPLACE, -1, 0);
+    int ret;
+
+    if (p == MAP_FAILED) {
+        return errno == EEXIST ? 0 : -1;
+    }
+    ret = p == (void *)addr;
+    if (!keep || !ret) {
+        munmap(p, size);
+    }
+    return ret;
 }
 
-static void pgb_have_guest_base(const char *image_name, abi_ulong guest_loaddr,
-                                abi_ulong guest_hiaddr, long align)
+/**
+ * pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t size, uintptr_t brk)
+ * @addr: host address
+ * @addr_last: host last address
+ * @brk: host brk
+ *
+ * Like pgb_try_mmap, but additionally reserve some memory following brk.
+ */
+static int pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t addr_last,
+                                 uintptr_t brk, bool keep)
 {
-    const int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE;
-    void *addr, *test;
+    uintptr_t brk_last = brk + 16 * MiB - 1;
 
-    if (!QEMU_IS_ALIGNED(guest_base, align)) {
-        fprintf(stderr, "Requested guest base %p does not satisfy "
-                "host minimum alignment (0x%lx)\n",
-                (void *)guest_base, align);
-        exit(EXIT_FAILURE);
+    /* Do not map anything close to the host brk. */
+    if (addr <= brk_last && brk <= addr_last) {
+        return 0;
     }
+    return pgb_try_mmap(addr, addr_last, keep);
+}
 
-    /* Sanity check the guest binary. */
-    if (reserved_va) {
-        if (guest_hiaddr > reserved_va) {
-            error_report("%s: requires more than reserved virtual "
-                         "address space (0x%" PRIx64 " > 0x%lx)",
-                         image_name, (uint64_t)guest_hiaddr, reserved_va);
-            exit(EXIT_FAILURE);
+/**
+ * pgb_try_mmap_set:
+ * @ga: set of guest addrs
+ * @base: guest_base
+ * @brk: host brk
+ *
+ * Return true if all @ga can be mapped by the host at @base.
+ * On success, retain the mapping at index 0 for reserved_va.
+ */
+
+typedef struct PGBAddrs {
+    uintptr_t bounds[3][2]; /* start/last pairs */
+    int nbounds;
+} PGBAddrs;
+
+static bool pgb_try_mmap_set(const PGBAddrs *ga, uintptr_t base, uintptr_t brk)
+{
+    for (int i = ga->nbounds - 1; i >= 0; --i) {
+        if (pgb_try_mmap_skip_brk(ga->bounds[i][0] + base,
+                                  ga->bounds[i][1] + base,
+                                  brk, i == 0 && reserved_va) <= 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
+/**
+ * pgb_addr_set:
+ * @ga: output set of guest addrs
+ * @guest_loaddr: guest image low address
+ * @guest_loaddr: guest image high address
+ * @identity: create for identity mapping
+ *
+ * Fill in @ga with the image, COMMPAGE and NULL page.
+ */
+static bool pgb_addr_set(PGBAddrs *ga, abi_ulong guest_loaddr,
+                         abi_ulong guest_hiaddr, bool try_identity)
+{
+    int n;
+
+    /*
+     * With a low commpage, or a guest mapped very low,
+     * we may not be able to use the identity map.
+     */
+    if (try_identity) {
+        if (LO_COMMPAGE != -1 && LO_COMMPAGE < mmap_min_addr) {
+            return false;
+        }
+        if (guest_loaddr != 0 && guest_loaddr < mmap_min_addr) {
+            return false;
         }
+    }
+
+    memset(ga, 0, sizeof(*ga));
+    n = 0;
+
+    if (reserved_va) {
+        ga->bounds[n][0] = try_identity ? mmap_min_addr : 0;
+        ga->bounds[n][1] = reserved_va;
+        n++;
+        /* LO_COMMPAGE and NULL handled by reserving from 0. */
     } else {
-#if HOST_LONG_BITS < TARGET_ABI_BITS
-        if ((guest_hiaddr - guest_base) > ~(uintptr_t)0) {
-            error_report("%s: requires more virtual address space "
-                         "than the host can provide (0x%" PRIx64 ")",
-                         image_name, (uint64_t)guest_hiaddr + 1 - guest_base);
-            exit(EXIT_FAILURE);
+        /* Add any LO_COMMPAGE or NULL page. */
+        if (LO_COMMPAGE != -1) {
+            ga->bounds[n][0] = 0;
+            ga->bounds[n][1] = LO_COMMPAGE + TARGET_PAGE_SIZE - 1;
+            n++;
+        } else if (!try_identity) {
+            ga->bounds[n][0] = 0;
+            ga->bounds[n][1] = TARGET_PAGE_SIZE - 1;
+            n++;
+        }
+
+        /* Add the guest image for ET_EXEC. */
+        if (guest_loaddr) {
+            ga->bounds[n][0] = guest_loaddr;
+            ga->bounds[n][1] = guest_hiaddr;
+            n++;
         }
-#endif
     }
 
     /*
-     * Expand the allocation to the entire reserved_va.
-     * Exclude the mmap_min_addr hole.
+     * Temporarily disable
+     *   "comparison is always false due to limited range of data type"
+     * due to comparison between unsigned and (possible) 0.
      */
-    if (reserved_va) {
-        guest_loaddr = (guest_base >= mmap_min_addr ? 0
-                        : mmap_min_addr - guest_base);
-        guest_hiaddr = reserved_va;
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wtype-limits"
+
+    /* Add any HI_COMMPAGE not covered by reserved_va. */
+    if (reserved_va < HI_COMMPAGE) {
+        ga->bounds[n][0] = HI_COMMPAGE & qemu_host_page_mask;
+        ga->bounds[n][1] = HI_COMMPAGE + TARGET_PAGE_SIZE - 1;
+        n++;
     }
 
-    /* Reserve the address space for the binary, or reserved_va. */
-    test = g2h_untagged(guest_loaddr);
-    addr = mmap(test, guest_hiaddr - guest_loaddr + 1, PROT_NONE, flags, -1, 0);
-    if (test != addr) {
+#pragma GCC diagnostic pop
+
+    ga->nbounds = n;
+    return true;
+}
+
+static void pgb_fail_in_use(const char *image_name)
+{
+    error_report("%s: requires virtual address space that is in use "
+                 "(omit the -B option or choose a different value)",
+                 image_name);
+    exit(EXIT_FAILURE);
+}
+
+static void pgb_fixed(const char *image_name, uintptr_t guest_loaddr,
+                      uintptr_t guest_hiaddr, uintptr_t align)
+{
+    PGBAddrs ga;
+    uintptr_t brk = (uintptr_t)sbrk(0);
+
+    if (!QEMU_IS_ALIGNED(guest_base, align)) {
+        fprintf(stderr, "Requested guest base %p does not satisfy "
+                "host minimum alignment (0x%" PRIxPTR ")\n",
+                (void *)guest_base, align);
+        exit(EXIT_FAILURE);
+    }
+
+    if (!pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, !guest_base)
+        || !pgb_try_mmap_set(&ga, guest_base, brk)) {
         pgb_fail_in_use(image_name);
     }
-    qemu_log_mask(CPU_LOG_PAGE,
-                  "%s: base @ %p for %" PRIu64 " bytes\n",
-                  __func__, addr, (uint64_t)guest_hiaddr - guest_loaddr + 1);
 }
 
 /**
- * pgd_find_hole_fallback: potential mmap address
- * @guest_size: size of available space
- * @brk: location of break
- * @align: memory alignment
+ * pgb_find_fallback:
  *
- * This is a fallback method for finding a hole in the host address
- * space if we don't have the benefit of being able to access
- * /proc/self/map. It can potentially take a very long time as we can
- * only dumbly iterate up the host address space seeing if the
- * allocation would work.
+ * This is a fallback method for finding holes in the host address space
+ * if we don't have the benefit of being able to access /proc/self/map.
+ * It can potentially take a very long time as we can only dumbly iterate
+ * up the host address space seeing if the allocation would work.
  */
-static uintptr_t pgd_find_hole_fallback(uintptr_t guest_size, uintptr_t brk,
-                                        long align, uintptr_t offset)
+static uintptr_t pgb_find_fallback(const PGBAddrs *ga, uintptr_t align,
+                                   uintptr_t brk)
 {
-    uintptr_t base;
-
-    /* Start (aligned) at the bottom and work our way up */
-    base = ROUND_UP(mmap_min_addr, align);
+    /* TODO: come up with a better estimate of how much to skip. */
+    uintptr_t skip = sizeof(uintptr_t) == 4 ? MiB : GiB;
 
-    while (true) {
-        uintptr_t align_start, end;
-        align_start = ROUND_UP(base, align);
-        end = align_start + guest_size + offset;
-
-        /* if brk is anywhere in the range give ourselves some room to grow. */
-        if (align_start <= brk && brk < end) {
-            base = brk + (16 * MiB);
-            continue;
-        } else if (align_start + guest_size < align_start) {
-            /* we have run out of space */
+    for (uintptr_t base = skip; ; base += skip) {
+        base = ROUND_UP(base, align);
+        if (pgb_try_mmap_set(ga, base, brk)) {
+            return base;
+        }
+        if (base >= -skip) {
             return -1;
-        } else {
-            int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE |
-                MAP_FIXED_NOREPLACE;
-            void * mmap_start = mmap((void *) align_start, guest_size,
-                                     PROT_NONE, flags, -1, 0);
-            if (mmap_start != MAP_FAILED) {
-                munmap(mmap_start, guest_size);
-                if (mmap_start == (void *) align_start) {
-                    qemu_log_mask(CPU_LOG_PAGE,
-                                  "%s: base @ %p for %" PRIdPTR" bytes\n",
-                                  __func__, mmap_start + offset, guest_size);
-                    return (uintptr_t) mmap_start + offset;
-                }
-            }
-            base += qemu_host_page_size;
         }
     }
 }
 
-/* Return value for guest_base, or -1 if no hole found. */
-static uintptr_t pgb_find_hole(uintptr_t guest_loaddr, uintptr_t guest_size,
-                               long align, uintptr_t offset)
+static uintptr_t pgb_try_itree(const PGBAddrs *ga, uintptr_t base,
+                               IntervalTreeRoot *root)
 {
-    GSList *maps, *iter;
-    uintptr_t this_start, this_end, next_start, brk;
-    intptr_t ret = -1;
-
-    assert(QEMU_IS_ALIGNED(guest_loaddr, align));
-
-    maps = read_self_maps();
-
-    /* Read brk after we've read the maps, which will malloc. */
-    brk = (uintptr_t)sbrk(0);
+    for (int i = ga->nbounds - 1; i >= 0; --i) {
+        uintptr_t s = base + ga->bounds[i][0];
+        uintptr_t l = base + ga->bounds[i][1];
+        IntervalTreeNode *n;
+
+        if (l < s) {
+            /* Wraparound. Skip to advance S to mmap_min_addr. */
+            return mmap_min_addr - s;
+        }
 
-    if (!maps) {
-        return pgd_find_hole_fallback(guest_size, brk, align, offset);
+        n = interval_tree_iter_first(root, s, l);
+        if (n != NULL) {
+            /* Conflict.  Skip to advance S to LAST + 1. */
+            return n->last - s + 1;
+        }
     }
+    return 0;  /* success */
+}
 
-    /* The first hole is before the first map entry. */
-    this_start = mmap_min_addr;
-
-    for (iter = maps; iter;
-         this_start = next_start, iter = g_slist_next(iter)) {
-        uintptr_t align_start, hole_size;
-
-        this_end = ((MapInfo *)iter->data)->start;
-        next_start = ((MapInfo *)iter->data)->end;
-        align_start = ROUND_UP(this_start + offset, align);
-
-        /* Skip holes that are too small. */
-        if (align_start >= this_end) {
-            continue;
-        }
-        hole_size = this_end - align_start;
-        if (hole_size < guest_size) {
-            continue;
-        }
+static uintptr_t pgb_find_itree(const PGBAddrs *ga, IntervalTreeRoot *root,
+                                uintptr_t align, uintptr_t brk)
+{
+    uintptr_t last = mmap_min_addr;
+    uintptr_t base, skip;
 
-        /* If this hole contains brk, give ourselves some room to grow. */
-        if (this_start <= brk && brk < this_end) {
-            hole_size -= guest_size;
-            if (sizeof(uintptr_t) == 8 && hole_size >= 1 * GiB) {
-                align_start += 1 * GiB;
-            } else if (hole_size >= 16 * MiB) {
-                align_start += 16 * MiB;
-            } else {
-                align_start = (this_end - guest_size) & -align;
-                if (align_start < this_start) {
-                    continue;
-                }
-            }
+    while (true) {
+        base = ROUND_UP(last, align);
+        if (base < last) {
+            return -1;
         }
 
-        /* Record the lowest successful match. */
-        if (ret < 0) {
-            ret = align_start;
-        }
-        /* If this hole contains the identity map, select it. */
-        if (align_start <= guest_loaddr &&
-            guest_loaddr + guest_size <= this_end) {
-            ret = 0;
-        }
-        /* If this hole ends above the identity map, stop looking. */
-        if (this_end >= guest_loaddr) {
+        skip = pgb_try_itree(ga, base, root);
+        if (skip == 0) {
             break;
         }
-    }
-    free_self_maps(maps);
 
-    if (ret != -1) {
-        qemu_log_mask(CPU_LOG_PAGE, "%s: base @ %" PRIxPTR
-                      " for %" PRIuPTR " bytes\n",
-                      __func__, ret, guest_size);
+        last = base + skip;
+        if (last < base) {
+            return -1;
+        }
     }
 
-    return ret;
+    /*
+     * We've chosen 'base' based on holes in the interval tree,
+     * but we don't yet know if it is a valid host address.
+     * Because it is the first matching hole, if the host addresses
+     * are invalid we know there are no further matches.
+     */
+    return pgb_try_mmap_set(ga, base, brk) ? base : -1;
 }
 
-static void pgb_static(const char *image_name, abi_ulong orig_loaddr,
-                       abi_ulong orig_hiaddr, long align)
+static void pgb_dynamic(const char *image_name, uintptr_t guest_loaddr,
+                        uintptr_t guest_hiaddr, uintptr_t align)
 {
-    uintptr_t loaddr = orig_loaddr;
-    uintptr_t hiaddr = orig_hiaddr;
-    uintptr_t offset = 0;
-    uintptr_t addr;
-
-    if (hiaddr != orig_hiaddr) {
-        error_report("%s: requires virtual address space that the "
-                     "host cannot provide (0x%" PRIx64 ")",
-                     image_name, (uint64_t)orig_hiaddr + 1);
-        exit(EXIT_FAILURE);
-    }
+    IntervalTreeRoot *root;
+    uintptr_t brk, ret;
+    PGBAddrs ga;
 
-    loaddr &= -align;
-    if (HI_COMMPAGE) {
-        /*
-         * Extend the allocation to include the commpage.
-         * For a 64-bit host, this is just 4GiB; for a 32-bit host we
-         * need to ensure there is space bellow the guest_base so we
-         * can map the commpage in the place needed when the address
-         * arithmetic wraps around.
-         */
-        if (sizeof(uintptr_t) == 8 || loaddr >= 0x80000000u) {
-            hiaddr = UINT32_MAX;
-        } else {
-            offset = -(HI_COMMPAGE & -align);
-        }
-    } else if (LO_COMMPAGE != -1) {
-        loaddr = MIN(loaddr, LO_COMMPAGE & -align);
-    }
+    assert(QEMU_IS_ALIGNED(guest_loaddr, align));
 
-    addr = pgb_find_hole(loaddr, hiaddr - loaddr + 1, align, offset);
-    if (addr == -1) {
-        /*
-         * If HI_COMMPAGE, there *might* be a non-consecutive allocation
-         * that can satisfy both.  But as the normal arm32 link base address
-         * is ~32k, and we extend down to include the commpage, making the
-         * overhead only ~96k, this is unlikely.
-         */
-        error_report("%s: Unable to allocate %#zx bytes of "
-                     "virtual address space", image_name,
-                     (size_t)(hiaddr - loaddr));
-        exit(EXIT_FAILURE);
+    /* Try the identity map first. */
+    if (pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, true)) {
+        brk = (uintptr_t)sbrk(0);
+        if (pgb_try_mmap_set(&ga, 0, brk)) {
+            guest_base = 0;
+            return;
+        }
     }
 
-    guest_base = addr;
-
-    qemu_log_mask(CPU_LOG_PAGE, "%s: base @ %"PRIxPTR" for %" PRIuPTR" bytes\n",
-                  __func__, addr, hiaddr - loaddr);
-}
-
-static void pgb_dynamic(const char *image_name, long align)
-{
     /*
-     * The executable is dynamic and does not require a fixed address.
-     * All we need is a commpage that satisfies align.
-     * If we do not need a commpage, leave guest_base == 0.
+     * Rebuild the address set for non-identity map.
+     * This differs in the mapping of the guest NULL page.
      */
-    if (HI_COMMPAGE) {
-        uintptr_t addr, commpage;
+    pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, false);
 
-        /* 64-bit hosts should have used reserved_va. */
-        assert(sizeof(uintptr_t) == 4);
+    root = read_self_maps();
+
+    /* Read brk after we've read the maps, which will malloc. */
+    brk = (uintptr_t)sbrk(0);
 
+    if (!root) {
+        ret = pgb_find_fallback(&ga, align, brk);
+    } else {
         /*
-         * By putting the commpage at the first hole, that puts guest_base
-         * just above that, and maximises the positive guest addresses.
+         * Reserve the area close to the host brk.
+         * This will be freed with the rest of the tree.
          */
-        commpage = HI_COMMPAGE & -align;
-        addr = pgb_find_hole(commpage, -commpage, align, 0);
-        assert(addr != -1);
-        guest_base = addr;
-    }
-}
+        IntervalTreeNode *b = g_new0(IntervalTreeNode, 1);
+        b->start = brk;
+        b->last = brk + 16 * MiB - 1;
+        interval_tree_insert(b, root);
 
-static void pgb_reserved_va(const char *image_name, abi_ulong guest_loaddr,
-                            abi_ulong guest_hiaddr, long align)
-{
-    int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE;
-    void *addr, *test;
-
-    if (guest_hiaddr > reserved_va) {
-        error_report("%s: requires more than reserved virtual "
-                     "address space (0x%" PRIx64 " > 0x%lx)",
-                     image_name, (uint64_t)guest_hiaddr, reserved_va);
-        exit(EXIT_FAILURE);
+        ret = pgb_find_itree(&ga, root, align, brk);
+        free_self_maps(root);
     }
 
-    /* Widen the "image" to the entire reserved address space. */
-    pgb_static(image_name, 0, reserved_va, align);
+    if (ret == -1) {
+        int w = TARGET_LONG_BITS / 4;
 
-    /* osdep.h defines this as 0 if it's missing */
-    flags |= MAP_FIXED_NOREPLACE;
+        error_report("%s: Unable to find a guest_base to satisfy all "
+                     "guest address mapping requirements", image_name);
 
-    /* Reserve the memory on the host. */
-    assert(guest_base != 0);
-    test = g2h_untagged(0);
-    addr = mmap(test, reserved_va + 1, PROT_NONE, flags, -1, 0);
-    if (addr == MAP_FAILED || addr != test) {
-        error_report("Unable to reserve 0x%lx bytes of virtual address "
-                     "space at %p (%s) for use as guest address space (check your "
-                     "virtual memory ulimit setting, mmap_min_addr or reserve less "
-                     "using qemu-user's -R option)",
-                     reserved_va + 1, test, strerror(errno));
+        for (int i = 0; i < ga.nbounds; ++i) {
+            error_printf("  %0*" PRIx64 "-%0*" PRIx64 "\n",
+                         w, (uint64_t)ga.bounds[i][0],
+                         w, (uint64_t)ga.bounds[i][1]);
+        }
         exit(EXIT_FAILURE);
     }
-
-    qemu_log_mask(CPU_LOG_PAGE, "%s: base @ %p for %lu bytes\n",
-                  __func__, addr, reserved_va + 1);
+    guest_base = ret;
 }
 
 void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
@@ -2833,25 +2828,33 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
     /* In order to use host shmat, we must be able to honor SHMLBA.  */
     uintptr_t align = MAX(SHMLBA, qemu_host_page_size);
 
+    /* Sanity check the guest binary. */
+    if (reserved_va) {
+        if (guest_hiaddr > reserved_va) {
+            error_report("%s: requires more than reserved virtual "
+                         "address space (0x%" PRIx64 " > 0x%lx)",
+                         image_name, (uint64_t)guest_hiaddr, reserved_va);
+            exit(EXIT_FAILURE);
+        }
+    } else {
+        if (guest_hiaddr != (uintptr_t)guest_hiaddr) {
+            error_report("%s: requires more virtual address space "
+                         "than the host can provide (0x%" PRIx64 ")",
+                         image_name, (uint64_t)guest_hiaddr + 1);
+            exit(EXIT_FAILURE);
+        }
+    }
+
     if (have_guest_base) {
-        pgb_have_guest_base(image_name, guest_loaddr, guest_hiaddr, align);
-    } else if (reserved_va) {
-        pgb_reserved_va(image_name, guest_loaddr, guest_hiaddr, align);
-    } else if (guest_loaddr) {
-        pgb_static(image_name, guest_loaddr, guest_hiaddr, align);
+        pgb_fixed(image_name, guest_loaddr, guest_hiaddr, align);
     } else {
-        pgb_dynamic(image_name, align);
+        pgb_dynamic(image_name, guest_loaddr, guest_hiaddr, align);
     }
 
     /* Reserve and initialize the commpage. */
     if (!init_guest_commpage()) {
-        /*
-         * With have_guest_base, the user has selected the address and
-         * we are trying to work with that.  Otherwise, we have selected
-         * free space and init_guest_commpage must succeeded.
-         */
-        assert(have_guest_base);
-        pgb_fail_in_use(image_name);
+        /* We have already probed for the commpage being free. */
+        g_assert_not_reached();
     }
 
     assert(QEMU_IS_ALIGNED(guest_base, align));
@@ -3107,28 +3110,9 @@ static void load_elf_image(const char *image_name, int image_fd,
         }
     }
 
-    if (pinterp_name != NULL) {
-        /*
-         * This is the main executable.
-         *
-         * Reserve extra space for brk.
-         * We hold on to this space while placing the interpreter
-         * and the stack, lest they be placed immediately after
-         * the data segment and block allocation from the brk.
-         *
-         * 16MB is chosen as "large enough" without being so large as
-         * to allow the result to not fit with a 32-bit guest on a
-         * 32-bit host. However some 64 bit guests (e.g. s390x)
-         * attempt to place their heap further ahead and currently
-         * nothing stops them smashing into QEMUs address space.
-         */
-#if TARGET_LONG_BITS == 64
-        info->reserve_brk = 32 * MiB;
-#else
-        info->reserve_brk = 16 * MiB;
-#endif
-        hiaddr += info->reserve_brk;
+    load_addr = loaddr;
 
+    if (pinterp_name != NULL) {
         if (ehdr->e_type == ET_EXEC) {
             /*
              * Make sure that the low address does not conflict with
@@ -3136,31 +3120,55 @@ 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 += elf_et_dyn_base;
+
+            /*
+             * TODO: Better support for mmap alignment is desirable.
+             * Since we do not have complete control over the guest
+             * address space, we prefer the kernel to choose some address
+             * rather than force the use of LOAD_ADDR via MAP_FIXED.
+             * But without MAP_FIXED we cannot guarantee alignment,
+             * only suggest it.
+             */
+            align = pow2ceil(info->alignment);
+            if (align) {
+                load_addr &= -align;
+            }
         }
     }
 
     /*
      * Reserve address space for all of this.
      *
-     * In the case of ET_EXEC, we supply MAP_FIXED so that we get
-     * exactly the address range that is required.
+     * In the case of ET_EXEC, we supply MAP_FIXED_NOREPLACE so that we get
+     * exactly the address range that is required.  Without reserved_va,
+     * the guest address space is not isolated.  We have attempted to avoid
+     * conflict with the host program itself via probe_guest_base, but using
+     * MAP_FIXED_NOREPLACE instead of MAP_FIXED provides an extra check.
      *
      * Otherwise this is ET_DYN, and we are searching for a location
      * that can hold the memory space required.  If the image is
-     * pre-linked, LOADDR will be non-zero, and the kernel should
+     * pre-linked, LOAD_ADDR will be non-zero, and the kernel should
      * honor that address if it happens to be free.
      *
      * 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),
+                            (ehdr->e_type == ET_EXEC ? MAP_FIXED_NOREPLACE : 0),
                             -1, 0);
     if (load_addr == -1) {
         goto exit_mmap;
@@ -3195,7 +3203,8 @@ static void load_elf_image(const char *image_name, int image_fd,
     info->end_code = 0;
     info->start_data = -1;
     info->end_data = 0;
-    info->brk = 0;
+    /* Usual start for brk is after all sections of the main executable. */
+    info->brk = TARGET_PAGE_ALIGN(hiaddr);
     info->elf_flags = ehdr->e_flags;
 
     prot_exec = PROT_EXEC;
@@ -3221,7 +3230,7 @@ static void load_elf_image(const char *image_name, int image_fd,
     for (i = 0; i < ehdr->e_phnum; i++) {
         struct elf_phdr *eppnt = phdr + i;
         if (eppnt->p_type == PT_LOAD) {
-            abi_ulong vaddr, vaddr_po, vaddr_ps, vaddr_ef, vaddr_em, vaddr_len;
+            abi_ulong vaddr, vaddr_po, vaddr_ps, vaddr_ef, vaddr_em;
             int elf_prot = 0;
 
             if (eppnt->p_flags & PF_R) {
@@ -3235,8 +3244,8 @@ static void load_elf_image(const char *image_name, int image_fd,
             }
 
             vaddr = load_bias + eppnt->p_vaddr;
-            vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr);
-            vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
+            vaddr_po = vaddr & ~TARGET_PAGE_MASK;
+            vaddr_ps = vaddr & TARGET_PAGE_MASK;
 
             vaddr_ef = vaddr + eppnt->p_filesz;
             vaddr_em = vaddr + eppnt->p_memsz;
@@ -3246,30 +3255,18 @@ static void load_elf_image(const char *image_name, int image_fd,
              * but no backing file segment.
              */
             if (eppnt->p_filesz != 0) {
-                vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po);
-                error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
-                                    MAP_PRIVATE | MAP_FIXED,
+                error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po,
+                                    elf_prot, MAP_PRIVATE | MAP_FIXED,
                                     image_fd, eppnt->p_offset - vaddr_po);
-
                 if (error == -1) {
                     goto exit_mmap;
                 }
+            }
 
-                /*
-                 * If the load segment requests extra zeros (e.g. bss), map it.
-                 */
-                if (eppnt->p_filesz < eppnt->p_memsz) {
-                    zero_bss(vaddr_ef, vaddr_em, elf_prot);
-                }
-            } else if (eppnt->p_memsz != 0) {
-                vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_memsz + vaddr_po);
-                error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
-                                    MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS,
-                                    -1, 0);
-
-                if (error == -1) {
-                    goto exit_mmap;
-                }
+            /* If the load segment requests extra zeros (e.g. bss), map it. */
+            if (vaddr_ef < vaddr_em &&
+                !zero_bss(vaddr_ef, vaddr_em, elf_prot)) {
+                goto exit_mmap;
             }
 
             /* Find the full program boundaries.  */
@@ -3289,9 +3286,6 @@ static void load_elf_image(const char *image_name, int image_fd,
                     info->end_data = vaddr_ef;
                 }
             }
-            if (vaddr_em > info->brk) {
-                info->brk = vaddr_em;
-            }
 #ifdef TARGET_MIPS
         } else if (eppnt->p_type == PT_MIPS_ABIFLAGS) {
             Mips_elf_abiflags_v0 abiflags;
@@ -3620,6 +3614,19 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
     if (elf_interpreter) {
         load_elf_interp(elf_interpreter, &interp_info, bprm->buf);
 
+        /*
+         * While unusual because of ELF_ET_DYN_BASE, if we are unlucky
+         * with the mappings the interpreter can be loaded above but
+         * near the main executable, which can leave very little room
+         * for the heap.
+         * If the current brk has less than 16MB, use the end of the
+         * interpreter.
+         */
+        if (interp_info.brk > info->brk &&
+            interp_info.load_bias - info->brk < 16 * MiB)  {
+            info->brk = interp_info.brk;
+        }
+
         /* If the program interpreter is one of these two, then assume
            an iBCS2 image.  Otherwise assume a native linux image.  */
 
@@ -3673,17 +3680,6 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
     bprm->core_dump = &elf_core_dump;
 #endif
 
-    /*
-     * If we reserved extra space for brk, release it now.
-     * The implementation of do_brk in syscalls.c expects to be able
-     * to mmap pages in this space.
-     */
-    if (info->reserve_brk) {
-        abi_ulong start_brk = TARGET_PAGE_ALIGN(info->brk);
-        abi_ulong end_brk = TARGET_PAGE_ALIGN(info->brk + info->reserve_brk);
-        target_munmap(start_brk, end_brk - start_brk);
-    }
-
     return 0;
 }
 
diff --git a/linux-user/hexagon/target_mman.h b/linux-user/hexagon/target_mman.h
index e7ba607..e6b5e2c 100644
--- a/linux-user/hexagon/target_mman.h
+++ b/linux-user/hexagon/target_mman.h
@@ -1 +1,14 @@
+/*
+ * arch/hexgon/include/asm/processor.h
+ * TASK_UNMAPPED_BASE        PAGE_ALIGN(TASK_SIZE / 3)
+ *
+ * arch/hexagon/include/asm/mem-layout.h
+ * TASK_SIZE                 PAGE_OFFSET
+ * PAGE_OFFSET               0xc0000000
+ */
+#define TASK_UNMAPPED_BASE   0x40000000
+
+/* arch/hexagon/include/asm/elf.h */
+#define ELF_ET_DYN_BASE      0x08000000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/hppa/target_mman.h b/linux-user/hppa/target_mman.h
index 97f87d0..ccda46e 100644
--- a/linux-user/hppa/target_mman.h
+++ b/linux-user/hppa/target_mman.h
@@ -24,6 +24,12 @@
 #define TARGET_MS_ASYNC 2
 #define TARGET_MS_INVALIDATE 4
 
+/* arch/parisc/include/asm/processor.h: DEFAULT_MAP_BASE32 */
+#define TASK_UNMAPPED_BASE      0x40000000
+
+/* arch/parisc/include/asm/elf.h */
+#define ELF_ET_DYN_BASE         (TASK_UNMAPPED_BASE + 0x01000000)
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/i386/target_mman.h b/linux-user/i386/target_mman.h
index e7ba607..e3b8e1e 100644
--- a/linux-user/i386/target_mman.h
+++ b/linux-user/i386/target_mman.h
@@ -1 +1,17 @@
+/*
+ * arch/x86/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         __TASK_UNMAPPED_BASE(TASK_SIZE_LOW)
+ * __TASK_UNMAPPED_BASE(S)    PAGE_ALIGN(S / 3)
+ *
+ * arch/x86/include/asm/page_32_types.h:
+ * TASK_SIZE_LOW              TASK_SIZE
+ * TASK_SIZE                  __PAGE_OFFSET
+ * __PAGE_OFFSET              CONFIG_PAGE_OFFSET
+ * CONFIG_PAGE_OFFSET         0xc0000000 (default in Kconfig)
+ */
+#define TASK_UNMAPPED_BASE    0x40000000
+
+/* arch/x86/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       0x00400000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/loongarch64/target_mman.h b/linux-user/loongarch64/target_mman.h
index e7ba607..8c2a3d5 100644
--- a/linux-user/loongarch64/target_mman.h
+++ b/linux-user/loongarch64/target_mman.h
@@ -1 +1,12 @@
+/*
+ * arch/loongarch/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         PAGE_ALIGN(TASK_SIZE / 3)
+ * TASK_SIZE64                0x1UL << (... ? VA_BITS : ...)
+ */
+#define TASK_UNMAPPED_BASE \
+    TARGET_PAGE_ALIGN((1ull << TARGET_VIRT_ADDR_SPACE_BITS) / 3)
+
+/* arch/loongarch/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/m68k/target_mman.h b/linux-user/m68k/target_mman.h
index e7ba607..20cfe75 100644
--- a/linux-user/m68k/target_mman.h
+++ b/linux-user/m68k/target_mman.h
@@ -1 +1,6 @@
+/* arch/m68k/include/asm/processor.h */
+#define TASK_UNMAPPED_BASE      0xC0000000
+/* arch/m68k/include/asm/elf.h */
+#define ELF_ET_DYN_BASE         0xD0000000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/main.c b/linux-user/main.c
index 556956c..96be354 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -821,6 +821,49 @@ int main(int argc, char **argv, char **envp)
         reserved_va = max_reserved_va;
     }
 
+    /*
+     * Temporarily disable
+     *   "comparison is always false due to limited range of data type"
+     * due to comparison between (possible) uint64_t and uintptr_t.
+     */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wtype-limits"
+
+    /*
+     * Select an initial value for task_unmapped_base that is in range.
+     */
+    if (reserved_va) {
+        if (TASK_UNMAPPED_BASE < reserved_va) {
+            task_unmapped_base = TASK_UNMAPPED_BASE;
+        } else {
+            /* The most common default formula is TASK_SIZE / 3. */
+            task_unmapped_base = TARGET_PAGE_ALIGN(reserved_va / 3);
+        }
+    } else if (TASK_UNMAPPED_BASE < UINTPTR_MAX) {
+        task_unmapped_base = TASK_UNMAPPED_BASE;
+    } else {
+        /* 32-bit host: pick something medium size. */
+        task_unmapped_base = 0x10000000;
+    }
+    mmap_next_start = task_unmapped_base;
+
+    /* Similarly for elf_et_dyn_base. */
+    if (reserved_va) {
+        if (ELF_ET_DYN_BASE < reserved_va) {
+            elf_et_dyn_base = ELF_ET_DYN_BASE;
+        } else {
+            /* The most common default formula is TASK_SIZE / 3 * 2. */
+            elf_et_dyn_base = TARGET_PAGE_ALIGN(reserved_va / 3) * 2;
+        }
+    } else if (ELF_ET_DYN_BASE < UINTPTR_MAX) {
+        elf_et_dyn_base = ELF_ET_DYN_BASE;
+    } else {
+        /* 32-bit host: pick something medium size. */
+        elf_et_dyn_base = 0x18000000;
+    }
+
+#pragma GCC diagnostic pop
+
     {
         Error *err = NULL;
         if (seed_optarg != NULL) {
diff --git a/linux-user/microblaze/target_mman.h b/linux-user/microblaze/target_mman.h
index e7ba607..6b3dd54 100644
--- a/linux-user/microblaze/target_mman.h
+++ b/linux-user/microblaze/target_mman.h
@@ -1 +1,12 @@
+/*
+ * arch/microblaze/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE           (TASK_SIZE / 8 * 3)
+ * TASK_SIZE                    CONFIG_KERNEL_START
+ * CONFIG_KERNEL_START          0xc0000000 (default in Kconfig)
+ */
+#define TASK_UNMAPPED_BASE      0x48000000
+
+/* arch/microblaze/include/uapi/asm/elf.h */
+#define ELF_ET_DYN_BASE         0x08000000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/mips/target_mman.h b/linux-user/mips/target_mman.h
index e97694a..b84fe1e 100644
--- a/linux-user/mips/target_mman.h
+++ b/linux-user/mips/target_mman.h
@@ -14,6 +14,16 @@
 #define TARGET_MAP_STACK                0x40000
 #define TARGET_MAP_HUGETLB              0x80000
 
+/*
+ * arch/mips/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         PAGE_ALIGN(TASK_SIZE / 3)
+ */
+#define TASK_UNMAPPED_BASE \
+    TARGET_PAGE_ALIGN((1ull << TARGET_VIRT_ADDR_SPACE_BITS) / 3)
+
+/* arch/mips/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index eb04fab..9aab48d 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -299,20 +299,9 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
     return true;
 }
 
-#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
-#ifdef TARGET_AARCH64
-# define TASK_UNMAPPED_BASE  0x5500000000
-#else
-# define TASK_UNMAPPED_BASE  (1ul << 38)
-#endif
-#else
-#ifdef TARGET_HPPA
-# define TASK_UNMAPPED_BASE  0xfa000000
-#else
-# define TASK_UNMAPPED_BASE  0x40000000
-#endif
-#endif
-abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
+abi_ulong task_unmapped_base;
+abi_ulong elf_et_dyn_base;
+abi_ulong mmap_next_start;
 
 /*
  * Subroutine of mmap_find_vma, used when we have pre-allocated
@@ -391,7 +380,7 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
 
             if ((addr & (align - 1)) == 0) {
                 /* Success.  */
-                if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
+                if (start == mmap_next_start && addr >= task_unmapped_base) {
                     mmap_next_start = addr + size;
                 }
                 return addr;
diff --git a/linux-user/nios2/target_mman.h b/linux-user/nios2/target_mman.h
index e7ba607..ab16ad4 100644
--- a/linux-user/nios2/target_mman.h
+++ b/linux-user/nios2/target_mman.h
@@ -1 +1,11 @@
+/*
+ * arch/nios2/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         PAGE_ALIGN(TASK_SIZE / 3)
+ * TASK_SIZE                  0x7FFF0000UL
+ */
+#define TASK_UNMAPPED_BASE    TARGET_PAGE_ALIGN(0x7FFF0000 / 3)
+
+/* arch/nios2/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       0xD0000000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/openrisc/target_mman.h b/linux-user/openrisc/target_mman.h
index e7ba607..243c1d5 100644
--- a/linux-user/openrisc/target_mman.h
+++ b/linux-user/openrisc/target_mman.h
@@ -1 +1,11 @@
+/*
+ * arch/openrisc/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE      (TASK_SIZE / 8 * 3)
+ * TASK_SIZE               (0x80000000UL)
+ */
+#define TASK_UNMAPPED_BASE      0x30000000
+
+/* arch/openrisc/include/asm/elf.h */
+#define ELF_ET_DYN_BASE         0x08000000
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/ppc/target_mman.h b/linux-user/ppc/target_mman.h
index 67cc218..646d1cc 100644
--- a/linux-user/ppc/target_mman.h
+++ b/linux-user/ppc/target_mman.h
@@ -4,6 +4,26 @@
 #define TARGET_MAP_NORESERVE            0x40
 #define TARGET_MAP_LOCKED               0x80
 
+/*
+ * arch/powerpc/include/asm/task_size_64.h
+ * TASK_UNMAPPED_BASE_USER32    (PAGE_ALIGN(TASK_SIZE_USER32 / 4))
+ * TASK_UNMAPPED_BASE_USER64    (PAGE_ALIGN(DEFAULT_MAP_WINDOW_USER64 / 4))
+ * TASK_SIZE_USER32             (0x0000000100000000UL - (1 * PAGE_SIZE))
+ * DEFAULT_MAP_WINDOW_USER64    TASK_SIZE_64TB (with 4k pages)
+ */
+#ifdef TARGET_PPC64
+#define TASK_UNMAPPED_BASE      0x0000100000000000ull
+#else
+#define TASK_UNMAPPED_BASE      0x40000000
+#endif
+
+/* arch/powerpc/include/asm/elf.h */
+#ifdef TARGET_PPC64
+#define ELF_ET_DYN_BASE         0x100000000ull
+#else
+#define ELF_ET_DYN_BASE         0x000400000
+#endif
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 2046a23..4f8b55e 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -30,7 +30,6 @@ struct image_info {
         abi_ulong       start_data;
         abi_ulong       end_data;
         abi_ulong       brk;
-        abi_ulong       reserve_brk;
         abi_ulong       start_mmap;
         abi_ulong       start_stack;
         abi_ulong       stack_limit;
diff --git a/linux-user/riscv/target_mman.h b/linux-user/riscv/target_mman.h
index e7ba607..3049bcc 100644
--- a/linux-user/riscv/target_mman.h
+++ b/linux-user/riscv/target_mman.h
@@ -1 +1,11 @@
+/*
+ * arch/loongarch/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         PAGE_ALIGN(TASK_SIZE / 3)
+ */
+#define TASK_UNMAPPED_BASE \
+    TARGET_PAGE_ALIGN((1ull << (TARGET_VIRT_ADDR_SPACE_BITS - 1)) / 3)
+
+/* arch/riscv/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/s390x/target_mman.h b/linux-user/s390x/target_mman.h
index e7ba607..c82435e 100644
--- a/linux-user/s390x/target_mman.h
+++ b/linux-user/s390x/target_mman.h
@@ -1 +1,21 @@
+/*
+ * arch/s390/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE           (... : (_REGION2_SIZE >> 1))
+ *
+ * arch/s390/include/asm/pgtable.h:
+ * _REGION2_SIZE                (1UL << _REGION2_SHIFT)
+ * _REGION2_SHIFT               42
+ */
+#define TASK_UNMAPPED_BASE      (1ull << 41)
+
+/*
+ * arch/s390/include/asm/elf.h:
+ * ELF_ET_DYN_BASE              (STACK_TOP / 3 * 2) & ~((1UL << 32) - 1)
+ *
+ * arch/s390/include/asm/processor.h:
+ * STACK_TOP                    VDSO_LIMIT - VDSO_SIZE - PAGE_SIZE
+ * VDSO_LIMIT                   _REGION2_SIZE
+ */
+#define ELF_ET_DYN_BASE         (((1ull << 42) / 3 * 2) & ~0xffffffffull)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/sh4/target_mman.h b/linux-user/sh4/target_mman.h
index e7ba607..dd90160 100644
--- a/linux-user/sh4/target_mman.h
+++ b/linux-user/sh4/target_mman.h
@@ -1 +1,8 @@
+/* arch/sh/include/asm/processor_32.h */
+#define TASK_UNMAPPED_BASE \
+    TARGET_PAGE_ALIGN((1u << TARGET_VIRT_ADDR_SPACE_BITS) / 3)
+
+/* arch/sh/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/sparc/target_mman.h b/linux-user/sparc/target_mman.h
index 9bad99c..696ca73 100644
--- a/linux-user/sparc/target_mman.h
+++ b/linux-user/sparc/target_mman.h
@@ -5,6 +5,31 @@
 #define TARGET_MAP_LOCKED              0x100
 #define TARGET_MAP_GROWSDOWN           0x0200
 
+/*
+ * arch/sparc/include/asm/page_64.h:
+ * TASK_UNMAPPED_BASE      (test_thread_flag(TIF_32BIT) ? \
+ *                          _AC(0x0000000070000000,UL) : \
+ *                          VA_EXCLUDE_END)
+ * But VA_EXCLUDE_END is > 0xffff800000000000UL which doesn't work
+ * in userland emulation.
+ */
+#ifdef TARGET_ABI32
+#define TASK_UNMAPPED_BASE      0x70000000
+#else
+#define TASK_UNMAPPED_BASE      (1ull << (TARGET_VIRT_ADDR_SPACE_BITS - 2))
+#endif
+
+/*
+ * arch/sparc/include/asm/elf_64.h
+ * Except that COMPAT_ELF_ET_DYN_BASE exactly matches TASK_UNMAPPED_BASE,
+ * so move it up a bit.
+ */
+#ifdef TARGET_ABI32
+#define ELF_ET_DYN_BASE         0x78000000
+#else
+#define ELF_ET_DYN_BASE         0x0000010000000000ull
+#endif
+
 #include "../generic/target_mman.h"
 
 #endif
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 7c2c2f6..a15bce2 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8070,16 +8070,17 @@ static int open_self_maps_1(CPUArchState *cpu_env, int fd, bool smaps)
 {
     CPUState *cpu = env_cpu(cpu_env);
     TaskState *ts = cpu->opaque;
-    GSList *map_info = read_self_maps();
-    GSList *s;
+    IntervalTreeRoot *map_info = read_self_maps();
+    IntervalTreeNode *s;
     int count;
 
-    for (s = map_info; s; s = g_slist_next(s)) {
-        MapInfo *e = (MapInfo *) s->data;
+    for (s = interval_tree_iter_first(map_info, 0, -1); s;
+         s = interval_tree_iter_next(s, 0, -1)) {
+        MapInfo *e = container_of(s, MapInfo, itree);
 
-        if (h2g_valid(e->start)) {
-            unsigned long min = e->start;
-            unsigned long max = e->end;
+        if (h2g_valid(e->itree.start)) {
+            unsigned long min = e->itree.start;
+            unsigned long max = e->itree.last + 1;
             int flags = page_get_flags(h2g(min));
             const char *path;
 
diff --git a/linux-user/user-mmap.h b/linux-user/user-mmap.h
index 7265c2c..0f4883e 100644
--- a/linux-user/user-mmap.h
+++ b/linux-user/user-mmap.h
@@ -18,6 +18,34 @@
 #ifndef LINUX_USER_USER_MMAP_H
 #define LINUX_USER_USER_MMAP_H
 
+/*
+ * Guest parameters for the ADDR_COMPAT_LAYOUT personality
+ * (at present this is the only layout supported by QEMU).
+ *
+ * TASK_UNMAPPED_BASE: For mmap without hint (addr != 0), the search
+ * for unused virtual memory begins at TASK_UNMAPPED_BASE.
+ *
+ * ELF_ET_DYN_BASE: When the executable is ET_DYN (i.e. PIE), and requires
+ * an interpreter (i.e. not -static-pie), use ELF_ET_DYN_BASE instead of
+ * TASK_UNMAPPED_BASE for selecting the address of the executable.
+ * This provides some distance between the executable and the interpreter,
+ * which allows the initial brk to be placed immediately after the
+ * executable and also have room to grow.
+ *
+ * task_unmapped_base, elf_et_dyn_base: When the guest address space is
+ * limited via -R, the values of TASK_UNMAPPED_BASE and ELF_ET_DYN_BASE
+ * must be adjusted to fit.
+ */
+extern abi_ulong task_unmapped_base;
+extern abi_ulong elf_et_dyn_base;
+
+/*
+ * mmap_next_start: The base address for the next mmap without hint,
+ * increased after each successful map, starting at task_unmapped_base.
+ * This is an optimization within QEMU and not part of ADDR_COMPAT_LAYOUT.
+ */
+extern abi_ulong mmap_next_start;
+
 int target_mprotect(abi_ulong start, abi_ulong len, int prot);
 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
                      int flags, int fd, off_t offset);
@@ -26,7 +54,6 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
                        abi_ulong new_size, unsigned long flags,
                        abi_ulong new_addr);
 abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice);
-extern abi_ulong mmap_next_start;
 abi_ulong mmap_find_vma(abi_ulong, abi_ulong, abi_ulong);
 void mmap_fork_start(void);
 void mmap_fork_end(int child);
diff --git a/linux-user/x86_64/target_mman.h b/linux-user/x86_64/target_mman.h
index e7ba607..48fbf20 100644
--- a/linux-user/x86_64/target_mman.h
+++ b/linux-user/x86_64/target_mman.h
@@ -1 +1,16 @@
+/*
+ * arch/x86/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE         __TASK_UNMAPPED_BASE(TASK_SIZE_LOW)
+ * __TASK_UNMAPPED_BASE(S)    PAGE_ALIGN(S / 3)
+ *
+ * arch/x86/include/asm/page_64_types.h:
+ * TASK_SIZE_LOW              DEFAULT_MAP_WINDOW
+ * DEFAULT_MAP_WINDOW         ((1UL << 47) - PAGE_SIZE)
+ */
+#define TASK_UNMAPPED_BASE \
+    TARGET_PAGE_ALIGN((1ull << TARGET_VIRT_ADDR_SPACE_BITS) / 3)
+
+/* arch/x86/include/asm/elf.h */
+#define ELF_ET_DYN_BASE       (TASK_UNMAPPED_BASE * 2)
+
 #include "../generic/target_mman.h"
diff --git a/linux-user/xtensa/target_mman.h b/linux-user/xtensa/target_mman.h
index 3933771..8fa6337 100644
--- a/linux-user/xtensa/target_mman.h
+++ b/linux-user/xtensa/target_mman.h
@@ -14,6 +14,16 @@
 #define TARGET_MAP_STACK                0x40000
 #define TARGET_MAP_HUGETLB              0x80000
 
+/*
+ * arch/xtensa/include/asm/processor.h:
+ * TASK_UNMAPPED_BASE           (TASK_SIZE / 2)
+ */
+#define TASK_UNMAPPED_BASE      (1u << (TARGET_VIRT_ADDR_SPACE_BITS - 1))
+
+/* arch/xtensa/include/asm/elf.h */
+#define ELF_ET_DYN_BASE \
+    TARGET_PAGE_ALIGN((1u << TARGET_VIRT_ADDR_SPACE_BITS) / 3)
+
 #include "../generic/target_mman.h"
 
 #endif