gdbstub: extend GByteArray to read register helpers

Instead of passing a pointer to memory now just extend the GByteArray
to all the read register helpers. They can then safely append their
data through the normal way. We don't bother with this abstraction for
write registers as we have already ensured the buffer being copied
from is the correct size.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Damien Hedde <damien.hedde@greensocs.com>

Message-Id: <20200316172155.971-15-alex.bennee@linaro.org>

2 files changed, 42 insertions, 19 deletions

diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
index 59e366b..30b909e 100644
--- a/include/exec/gdbstub.h
+++ b/include/exec/gdbstub.h
@@ -68,53 +68,76 @@ void gdb_signalled(CPUArchState *, int);
 void gdbserver_fork(CPUState *);
 #endif
 /* Get or set a register.  Returns the size of the register.  */
-typedef int (*gdb_reg_cb)(CPUArchState *env, uint8_t *buf, int reg);
+typedef int (*gdb_get_reg_cb)(CPUArchState *env, GByteArray *buf, int reg);
+typedef int (*gdb_set_reg_cb)(CPUArchState *env, uint8_t *buf, int reg);
 void gdb_register_coprocessor(CPUState *cpu,
-                              gdb_reg_cb get_reg, gdb_reg_cb set_reg,
+                              gdb_get_reg_cb get_reg, gdb_set_reg_cb set_reg,
                               int num_regs, const char *xml, int g_pos);
 
-/* The GDB remote protocol transfers values in target byte order.  This means
- * we can use the raw memory access routines to access the value buffer.
- * Conveniently, these also handle the case where the buffer is mis-aligned.
+/*
+ * The GDB remote protocol transfers values in target byte order. As
+ * the gdbstub may be batching up several register values we always
+ * append to the array.
  */
 
-static inline int gdb_get_reg8(uint8_t *mem_buf, uint8_t val)
+static inline int gdb_get_reg8(GByteArray *buf, uint8_t val)
 {
-    stb_p(mem_buf, val);
+    g_byte_array_append(buf, &val, 1);
     return 1;
 }
 
-static inline int gdb_get_reg16(uint8_t *mem_buf, uint16_t val)
+static inline int gdb_get_reg16(GByteArray *buf, uint16_t val)
 {
-    stw_p(mem_buf, val);
+    uint16_t to_word = tswap16(val);
+    g_byte_array_append(buf, (uint8_t *) &to_word, 2);
     return 2;
 }
 
-static inline int gdb_get_reg32(uint8_t *mem_buf, uint32_t val)
+static inline int gdb_get_reg32(GByteArray *buf, uint32_t val)
 {
-    stl_p(mem_buf, val);
+    uint32_t to_long = tswap32(val);
+    g_byte_array_append(buf, (uint8_t *) &to_long, 4);
     return 4;
 }
 
-static inline int gdb_get_reg64(uint8_t *mem_buf, uint64_t val)
+static inline int gdb_get_reg64(GByteArray *buf, uint64_t val)
 {
-    stq_p(mem_buf, val);
+    uint64_t to_quad = tswap64(val);
+    g_byte_array_append(buf, (uint8_t *) &to_quad, 8);
     return 8;
 }
 
-static inline int gdb_get_reg128(uint8_t *mem_buf, uint64_t val_hi,
+static inline int gdb_get_reg128(GByteArray *buf, uint64_t val_hi,
                                  uint64_t val_lo)
 {
+    uint64_t to_quad;
 #ifdef TARGET_WORDS_BIGENDIAN
-    stq_p(mem_buf, val_hi);
-    stq_p(mem_buf + 8, val_lo);
+    to_quad = tswap64(val_hi);
+    g_byte_array_append(buf, (uint8_t *) &to_quad, 8);
+    to_quad = tswap64(val_lo);
+    g_byte_array_append(buf, (uint8_t *) &to_quad, 8);
 #else
-    stq_p(mem_buf, val_lo);
-    stq_p(mem_buf + 8, val_hi);
+    to_quad = tswap64(val_lo);
+    g_byte_array_append(buf, (uint8_t *) &to_quad, 8);
+    to_quad = tswap64(val_hi);
+    g_byte_array_append(buf, (uint8_t *) &to_quad, 8);
 #endif
     return 16;
 }
 
+/**
+ * gdb_get_reg_ptr: get pointer to start of last element
+ * @len: length of element
+ *
+ * This is a helper function to extract the pointer to the last
+ * element for additional processing. Some front-ends do additional
+ * dynamic swapping of the elements based on CPU state.
+ */
+static inline uint8_t * gdb_get_reg_ptr(GByteArray *buf, int len)
+{
+    return buf->data + buf->len - len;
+}
+
 #if TARGET_LONG_BITS == 64
 #define gdb_get_regl(buf, val) gdb_get_reg64(buf, val)
 #define ldtul_p(addr) ldq_p(addr)
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 73e9a86..e1d6ee0 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -195,7 +195,7 @@ typedef struct CPUClass {
     hwaddr (*get_phys_page_attrs_debug)(CPUState *cpu, vaddr addr,
                                         MemTxAttrs *attrs);
     int (*asidx_from_attrs)(CPUState *cpu, MemTxAttrs attrs);
-    int (*gdb_read_register)(CPUState *cpu, uint8_t *buf, int reg);
+    int (*gdb_read_register)(CPUState *cpu, GByteArray *buf, int reg);
     int (*gdb_write_register)(CPUState *cpu, uint8_t *buf, int reg);
     bool (*debug_check_watchpoint)(CPUState *cpu, CPUWatchpoint *wp);
     void (*debug_excp_handler)(CPUState *cpu);