linux-user: Create vdso_sigreturn_region_{start,end}

These variables will be populated from the vdso, and used
for detecting whether we are executing the sigreturn.

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

linux-user/elfload.c

@@ -1659,6 +1659,11 @@ static void load_elf_vdso(struct image_info *info, const VdsoImageInfo *vdso)
     if (vdso->rt_sigreturn_ofs) {
         default_rt_sigreturn = load_addr + vdso->rt_sigreturn_ofs;
     }
+    if (vdso->sigreturn_region_start_ofs) {
+        vdso_sigreturn_region_start =
+            load_addr + vdso->sigreturn_region_start_ofs;
+        vdso_sigreturn_region_end = load_addr + vdso->sigreturn_region_end_ofs;
+    }
 
     /* Remove write from VDSO segment. */
     target_mprotect(info->start_data, info->end_data - info->start_data,

linux-user/gen-vdso-elfn.c.inc

@@ -84,9 +84,12 @@ static void elfN(search_symtab)(ElfN(Shdr) *shdr, unsigned sym_idx,
 
         if (sigreturn_sym && strcmp(sigreturn_sym, name) == 0) {
             sigreturn_addr = sym.st_value;
-        }
+        } else if (rt_sigreturn_sym && strcmp(rt_sigreturn_sym, name) == 0) {
-        if (rt_sigreturn_sym && strcmp(rt_sigreturn_sym, name) == 0) {
             rt_sigreturn_addr = sym.st_value;
+        } else if (strcmp("sigreturn_region_start", name) == 0) {
+            sigreturn_region_start_addr = sym.st_value;
+        } else if (strcmp("sigreturn_region_end", name) == 0) {
+            sigreturn_region_end_addr = sym.st_value;
         }
     }
 }

linux-user/gen-vdso.c

@@ -36,6 +36,8 @@ static const char *rt_sigreturn_sym;
 
 static unsigned sigreturn_addr;
 static unsigned rt_sigreturn_addr;
+static unsigned sigreturn_region_start_addr;
+static unsigned sigreturn_region_end_addr;
 
 #define N 32
 #define elfN(x)  elf32_##x
@@ -215,6 +217,10 @@ int main(int argc, char **argv)
     fprintf(outf, "    .reloc_count = ARRAY_SIZE(%s_relocs),\n", prefix);
     fprintf(outf, "    .sigreturn_ofs = 0x%x,\n", sigreturn_addr);
     fprintf(outf, "    .rt_sigreturn_ofs = 0x%x,\n", rt_sigreturn_addr);
+    fprintf(outf, "    .sigreturn_region_start_ofs = 0x%x,\n",
+            sigreturn_region_start_addr);
+    fprintf(outf, "    .sigreturn_region_end_ofs = 0x%x,\n",
+            sigreturn_region_end_addr);
     fprintf(outf, "};\n");
 
     ret = EXIT_SUCCESS;

linux-user/loader.h

@@ -117,6 +117,8 @@ typedef struct {
     unsigned reloc_count;
     unsigned sigreturn_ofs;
     unsigned rt_sigreturn_ofs;
+    unsigned sigreturn_region_start_ofs;
+    unsigned sigreturn_region_end_ofs;
 } VdsoImageInfo;
 
 /* Note that both Elf32_Word and Elf64_Word are uint32_t. */

linux-user/signal-common.h

@@ -25,6 +25,8 @@
 /* Fallback addresses into sigtramp page. */
 extern abi_ulong default_sigreturn;
 extern abi_ulong default_rt_sigreturn;
+extern abi_ulong vdso_sigreturn_region_start;
+extern abi_ulong vdso_sigreturn_region_end;
 
 void setup_sigtramp(abi_ulong tramp_page);
 

linux-user/signal.c

@@ -50,6 +50,8 @@ static void host_signal_handler(int host_signum, siginfo_t *info,
 /* Fallback addresses into sigtramp page. */
 abi_ulong default_sigreturn;
 abi_ulong default_rt_sigreturn;
+abi_ulong vdso_sigreturn_region_start;
+abi_ulong vdso_sigreturn_region_end;
 
 /*
  * System includes define _NSIG as SIGRTMAX + 1, but qemu (like the kernel)