[Qemu-devel] [PATCH v6 3/6] linux-user: Set PAGE_TARGET_1 for TARGET_PROT_BTI

[Richard Henderson <richard.henderson@linaro.org>]

Transform the prot bit to a qemu internal page bit, and save
it in the page tables.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h     |  2 ++
 linux-user/syscall_defs.h  |  4 ++++
 linux-user/mmap.c          | 16 ++++++++++++++++
 target/arm/translate-a64.c |  6 +++---
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index da07ce311f..e65530acae 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -249,6 +249,8 @@ extern intptr_t qemu_host_page_mask;
 /* FIXME: Code that sets/uses this is broken and needs to go away.  */
 #define PAGE_RESERVED  0x0020
 #endif
+/* Target-specific bits that will be used via page_get_flags().  */
+#define PAGE_TARGET_1  0x0080
 
 #if defined(CONFIG_USER_ONLY)
 void page_dump(FILE *f);
diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index 7f141f699c..9a8a14e81e 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -1097,6 +1097,10 @@ struct target_winsize {
 #define TARGET_PROT_SEM         0x08
 #endif
 
+#ifdef TARGET_AARCH64
+#define TARGET_PROT_BTI         0x10
+#endif
+
 /* Common */
 #define TARGET_MAP_SHARED	0x01		/* Share changes */
 #define TARGET_MAP_PRIVATE	0x02		/* Changes are private */
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 3117f57fd8..def64a41d5 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -85,6 +85,22 @@ static int validate_prot_to_pageflags(int *host_prot, int prot)
      */
     *host_prot = prot & (PROT_READ | PROT_WRITE | PROT_EXEC);
 
+#ifdef TARGET_AARCH64
+    /*
+     * The PROT_BTI bit is only accepted if the cpu supports the feature.
+     * Since this is the unusual case, don't bother checking unless
+     * the bit has been requested.  If set and valid, record the bit
+     * within QEMU's page_flags as PAGE_TARGET_1.
+     */
+    if (prot & TARGET_PROT_BTI) {
+        ARMCPU *cpu = ARM_CPU(thread_cpu);
+        if (cpu_isar_feature(aa64_bti, cpu)) {
+            valid |= TARGET_PROT_BTI;
+            page_flags |= PAGE_TARGET_1;
+        }
+    }
+#endif
+
     return prot & ~valid ? 0 : page_flags;
 }
 
diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 092f0df3c4..5043344eba 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -14115,10 +14115,10 @@ static void disas_data_proc_simd_fp(DisasContext *s, uint32_t insn)
  */
 static bool is_guarded_page(CPUARMState *env, DisasContext *s)
 {
-#ifdef CONFIG_USER_ONLY
-    return false;  /* FIXME */
-#else
     uint64_t addr = s->base.pc_first;
+#ifdef CONFIG_USER_ONLY
+    return page_get_flags(addr) & PAGE_TARGET_1;
+#else
     int mmu_idx = arm_to_core_mmu_idx(s->mmu_idx);
     unsigned int index = tlb_index(env, mmu_idx, addr);
     CPUTLBEntry *entry = tlb_entry(env, mmu_idx, addr);
-- 
2.17.1