metag: ptrace: Implement NT_METAG_TLS

Implement functionality to get the TLS pointer for the metag
architecture using regsets.

This provides multi-threaded debug support for GDB.

Signed-off-by: Paul Clothier <Paul.Clothier@imgtec.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/arch/metag/kernel/ptrace.c b/arch/metag/kernel/ptrace.c
index 47a8828615a5..7563628822bd 100644
--- a/arch/metag/kernel/ptrace.c
+++ b/arch/metag/kernel/ptrace.c
@@ -288,10 +288,36 @@ static int metag_rp_state_set(struct task_struct *target,
         return metag_rp_state_copyin(regs, pos, count, kbuf, ubuf);
 }
 
+static int metag_tls_get(struct task_struct *target,
+                        const struct user_regset *regset,
+                        unsigned int pos, unsigned int count,
+                        void *kbuf, void __user *ubuf)
+{
+        void __user *tls = target->thread.tls_ptr;
+        return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &tls, 0, -1);
+}
+
+static int metag_tls_set(struct task_struct *target,
+                        const struct user_regset *regset,
+                        unsigned int pos, unsigned int count,
+                        const void *kbuf, const void __user *ubuf)
+{
+        int ret;
+        void __user *tls;
+
+        ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &tls, 0, -1);
+        if (ret)
+                return ret;
+
+        target->thread.tls_ptr = tls;
+        return ret;
+}
+
 enum metag_regset {
         REGSET_GENERAL,
         REGSET_CBUF,
         REGSET_READPIPE,
+        REGSET_TLS,
 };
 
 static const struct user_regset metag_regsets[] = {
@@ -319,6 +345,14 @@ static const struct user_regset metag_regsets[] = {
                 .get = metag_rp_state_get,
                 .set = metag_rp_state_set,
         },
+        [REGSET_TLS] = {
+                .core_note_type = NT_METAG_TLS,
+                .n = 1,
+                .size = sizeof(void *),
+                .align = sizeof(void *),
+                .get = metag_tls_get,
+                .set = metag_tls_set,
+        },
 };
 
 static const struct user_regset_view user_metag_view = {
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 8072d352b98f..ef6103bf1f9b 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -397,6 +397,7 @@ typedef struct elf64_shdr {
 #define NT_ARM_HW_WATCH 0x403           /* ARM hardware watchpoint registers */
 #define NT_METAG_CBUF   0x500           /* Metag catch buffer registers */
 #define NT_METAG_RPIPE  0x501           /* Metag read pipeline state */
+#define NT_METAG_TLS    0x502           /* Metag TLS pointer */
 
 
 /* Note header in a PT_NOTE section */