linux-user: Honor PT_GNU_STACK

Map the stack executable if required by default or on demand.

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/elf.h

@@ -31,6 +31,7 @@ typedef int64_t  Elf64_Sxword;
 #define PT_LOPROC  0x70000000
 #define PT_HIPROC  0x7fffffff
 
+#define PT_GNU_STACK      (PT_LOOS + 0x474e551)
 #define PT_GNU_PROPERTY   (PT_LOOS + 0x474e553)
 
 #define PT_MIPS_REGINFO   0x70000000

linux-user/elfload.c

@@ -232,6 +232,7 @@ static bool init_guest_commpage(void)
 #define ELF_ARCH        EM_386
 
 #define ELF_PLATFORM get_elf_platform()
+#define EXSTACK_DEFAULT true
 
 static const char *get_elf_platform(void)
 {
@@ -308,6 +309,7 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUX86State *en
 
 #define ELF_ARCH        EM_ARM
 #define ELF_CLASS       ELFCLASS32
+#define EXSTACK_DEFAULT true
 
 static inline void init_thread(struct target_pt_regs *regs,
                                struct image_info *infop)
@@ -776,6 +778,7 @@ static inline void init_thread(struct target_pt_regs *regs,
 #else
 
 #define ELF_CLASS       ELFCLASS32
+#define EXSTACK_DEFAULT true
 
 #endif
 
@@ -973,6 +976,7 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUPPCState *en
 
 #define ELF_CLASS   ELFCLASS64
 #define ELF_ARCH    EM_LOONGARCH
+#define EXSTACK_DEFAULT true
 
 #define elf_check_arch(x) ((x) == EM_LOONGARCH)
 
@@ -1068,6 +1072,7 @@ static uint32_t get_elf_hwcap(void)
 #define ELF_CLASS   ELFCLASS32
 #endif
 #define ELF_ARCH    EM_MIPS
+#define EXSTACK_DEFAULT true
 
 #ifdef TARGET_ABI_MIPSN32
 #define elf_check_abi(x) ((x) & EF_MIPS_ABI2)
@@ -1806,6 +1811,10 @@ static inline void init_thread(struct target_pt_regs *regs,
 #define bswaptls(ptr) bswap32s(ptr)
 #endif
 
+#ifndef EXSTACK_DEFAULT
+#define EXSTACK_DEFAULT false
+#endif
+
 #include "elf.h"
 
 /* We must delay the following stanzas until after "elf.h". */
@@ -2081,6 +2090,7 @@ static abi_ulong setup_arg_pages(struct linux_binprm *bprm,
                                  struct image_info *info)
 {
     abi_ulong size, error, guard;
+    int prot;
 
     size = guest_stack_size;
     if (size < STACK_LOWER_LIMIT) {
@@ -2091,7 +2101,11 @@ static abi_ulong setup_arg_pages(struct linux_binprm *bprm,
         guard = qemu_real_host_page_size();
     }
 
-    error = target_mmap(0, size + guard, PROT_READ | PROT_WRITE,
+    prot = PROT_READ | PROT_WRITE;
+    if (info->exec_stack) {
+        prot |= PROT_EXEC;
+    }
+    error = target_mmap(0, size + guard, prot,
                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (error == -1) {
         perror("mmap stack");
@@ -2921,6 +2935,7 @@ static void load_elf_image(const char *image_name, int image_fd,
      */
     loaddr = -1, hiaddr = 0;
     info->alignment = 0;
+    info->exec_stack = EXSTACK_DEFAULT;
     for (i = 0; i < ehdr->e_phnum; ++i) {
         struct elf_phdr *eppnt = phdr + i;
         if (eppnt->p_type == PT_LOAD) {
@@ -2963,6 +2978,8 @@ static void load_elf_image(const char *image_name, int image_fd,
             if (!parse_elf_properties(image_fd, info, eppnt, bprm_buf, &err)) {
                 goto exit_errmsg;
             }
+        } else if (eppnt->p_type == PT_GNU_STACK) {
+            info->exec_stack = eppnt->p_flags & PF_X;
         }
     }
 

linux-user/qemu.h

@@ -48,6 +48,7 @@ struct image_info {
         uint32_t        elf_flags;
         int             personality;
         abi_ulong       alignment;
+        bool            exec_stack;
 
         /* Generic semihosting knows about these pointers. */
         abi_ulong       arg_strings;   /* strings for argv */