[PULL 40/41] linux-user/elfload: Parse GNU_PROPERTY_AARCH64_FEATURE_1_AND

[Peter Maydell <peter.maydell@linaro.org>]

From: Richard Henderson <richard.henderson@linaro.org>

Use the new generic support for NT_GNU_PROPERTY_TYPE_0.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201016184207.786698-12-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/elfload.c | 48 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 46 insertions(+), 2 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 428dcaa1528..bf8c1bd2533 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1522,6 +1522,28 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs,
 
 #include "elf.h"
 
+/* We must delay the following stanzas until after "elf.h". */
+#if defined(TARGET_AARCH64)
+
+static bool arch_parse_elf_property(uint32_t pr_type, uint32_t pr_datasz,
+                                    const uint32_t *data,
+                                    struct image_info *info,
+                                    Error **errp)
+{
+    if (pr_type == GNU_PROPERTY_AARCH64_FEATURE_1_AND) {
+        if (pr_datasz != sizeof(uint32_t)) {
+            error_setg(errp, "Ill-formed GNU_PROPERTY_AARCH64_FEATURE_1_AND");
+            return false;
+        }
+        /* We will extract GNU_PROPERTY_AARCH64_FEATURE_1_BTI later. */
+        info->note_flags = *data;
+    }
+    return true;
+}
+#define ARCH_USE_GNU_PROPERTY 1
+
+#else
+
 static bool arch_parse_elf_property(uint32_t pr_type, uint32_t pr_datasz,
                                     const uint32_t *data,
                                     struct image_info *info,
@@ -1531,6 +1553,8 @@ static bool arch_parse_elf_property(uint32_t pr_type, uint32_t pr_datasz,
 }
 #define ARCH_USE_GNU_PROPERTY 0
 
+#endif
+
 struct exec
 {
     unsigned int a_info;   /* Use macros N_MAGIC, etc for access */
@@ -2545,7 +2569,7 @@ static void load_elf_image(const char *image_name, int image_fd,
     struct elfhdr *ehdr = (struct elfhdr *)bprm_buf;
     struct elf_phdr *phdr;
     abi_ulong load_addr, load_bias, loaddr, hiaddr, error;
-    int i, retval;
+    int i, retval, prot_exec;
     Error *err = NULL;
 
     /* First of all, some simple consistency checks */
@@ -2712,6 +2736,26 @@ static void load_elf_image(const char *image_name, int image_fd,
     info->brk = 0;
     info->elf_flags = ehdr->e_flags;
 
+    prot_exec = PROT_EXEC;
+#ifdef TARGET_AARCH64
+    /*
+     * If the BTI feature is present, this indicates that the executable
+     * pages of the startup binary should be mapped with PROT_BTI, so that
+     * branch targets are enforced.
+     *
+     * The startup binary is either the interpreter or the static executable.
+     * The interpreter is responsible for all pages of a dynamic executable.
+     *
+     * Elf notes are backward compatible to older cpus.
+     * Do not enable BTI unless it is supported.
+     */
+    if ((info->note_flags & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)
+        && (pinterp_name == NULL || *pinterp_name == 0)
+        && cpu_isar_feature(aa64_bti, ARM_CPU(thread_cpu))) {
+        prot_exec |= TARGET_PROT_BTI;
+    }
+#endif
+
     for (i = 0; i < ehdr->e_phnum; i++) {
         struct elf_phdr *eppnt = phdr + i;
         if (eppnt->p_type == PT_LOAD) {
@@ -2725,7 +2769,7 @@ static void load_elf_image(const char *image_name, int image_fd,
                 elf_prot |= PROT_WRITE;
             }
             if (eppnt->p_flags & PF_X) {
-                elf_prot |= PROT_EXEC;
+                elf_prot |= prot_exec;
             }
 
             vaddr = load_bias + eppnt->p_vaddr;
-- 
2.20.1