linux-user: Move init_guest_commpage to arm/elfload.c

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 48 insertions, 0 deletions

diff --git a/linux-user/arm/elfload.c b/linux-user/arm/elfload.c
index f811c2f07a..1205687976 100644
--- a/linux-user/arm/elfload.c
+++ b/linux-user/arm/elfload.c
@@ -3,6 +3,8 @@
 #include "qemu/osdep.h"
 #include "qemu.h"
 #include "loader.h"
+#include "user-internals.h"
+#include "target_elf.h"
 #include "target/arm/cpu-features.h"
 #include "target_elf.h"
 
@@ -201,6 +203,50 @@ const char *get_elf_platform(CPUState *cs)
 #undef END
 }
 
+bool init_guest_commpage(void)
+{
+    ARMCPU *cpu = ARM_CPU(thread_cpu);
+    int host_page_size = qemu_real_host_page_size();
+    abi_ptr commpage;
+    void *want;
+    void *addr;
+
+    /*
+     * M-profile allocates maximum of 2GB address space, so can never
+     * allocate the commpage.  Skip it.
+     */
+    if (arm_feature(&cpu->env, ARM_FEATURE_M)) {
+        return true;
+    }
+
+    commpage = HI_COMMPAGE & -host_page_size;
+    want = g2h_untagged(commpage);
+    addr = mmap(want, host_page_size, PROT_READ | PROT_WRITE,
+                MAP_ANONYMOUS | MAP_PRIVATE |
+                (commpage < reserved_va ? MAP_FIXED : MAP_FIXED_NOREPLACE),
+                -1, 0);
+
+    if (addr == MAP_FAILED) {
+        perror("Allocating guest commpage");
+        exit(EXIT_FAILURE);
+    }
+    if (addr != want) {
+        return false;
+    }
+
+    /* Set kernel helper versions; rest of page is 0.  */
+    __put_user(5, (uint32_t *)g2h_untagged(0xffff0ffcu));
+
+    if (mprotect(addr, host_page_size, PROT_READ)) {
+        perror("Protecting guest commpage");
+        exit(EXIT_FAILURE);
+    }
+
+    page_set_flags(commpage, commpage | (host_page_size - 1),
+                   PAGE_READ | PAGE_EXEC | PAGE_VALID);
+    return true;
+}
+
 void elf_core_copy_regs(target_elf_gregset_t *r, const CPUARMState *env)
 {
     for (int i = 0; i < 16; ++i) {
diff --git a/linux-user/arm/target_elf.h b/linux-user/arm/target_elf.h
index fa8f8af2f3..5f81a43efb 100644
--- a/linux-user/arm/target_elf.h
+++ b/linux-user/arm/target_elf.h
@@ -15,6 +15,8 @@
 #define HAVE_ELF_PLATFORM       1
 #define HAVE_ELF_CORE_DUMP      1
 
+#define HI_COMMPAGE             ((intptr_t)0xffff0f00u)
+
 /*
  * See linux kernel: arch/arm/include/asm/elf.h, where
  * elf_gregset_t is mapped to struct pt_regs via sizeof.