target/i386/gdbstub: Expose orig_ax

Copy XML files describing orig_ax from GDB and glue them with
CPUX86State.orig_ax.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-ID: <20240912093012.402366-5-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

configs/targets/i386-linux-user.mak

@@ -1,4 +1,4 @@
 TARGET_ARCH=i386
 TARGET_SYSTBL_ABI=i386
 TARGET_SYSTBL=syscall_32.tbl
-TARGET_XML_FILES= gdb-xml/i386-32bit.xml
+TARGET_XML_FILES= gdb-xml/i386-32bit.xml gdb-xml/i386-32bit-linux.xml

configs/targets/x86_64-linux-user.mak

@@ -2,4 +2,4 @@ TARGET_ARCH=x86_64
 TARGET_BASE_ARCH=i386
 TARGET_SYSTBL_ABI=common,64
 TARGET_SYSTBL=syscall_64.tbl
-TARGET_XML_FILES= gdb-xml/i386-64bit.xml
+TARGET_XML_FILES= gdb-xml/i386-64bit.xml gdb-xml/i386-64bit-linux.xml

gdb-xml/i386-32bit-linux.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2010-2024 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.i386.linux">
+  <reg name="orig_eax" bitsize="32" type="int"/>
+</feature>

gdb-xml/i386-64bit-linux.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2010-2024 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.i386.linux">
+  <reg name="orig_rax" bitsize="64" type="int"/>
+</feature>

target/i386/cpu.c

@@ -7831,6 +7831,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
 
     mce_init(cpu);
 
+    x86_cpu_gdb_init(cs);
     qemu_init_vcpu(cs);
 
     /*

target/i386/cpu.h

@@ -2226,6 +2226,7 @@ void x86_cpu_dump_state(CPUState *cs, FILE *f, int flags);
 
 int x86_cpu_gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
 int x86_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
+void x86_cpu_gdb_init(CPUState *cs);
 
 void x86_cpu_list(void);
 int cpu_x86_support_mca_broadcast(CPUX86State *env);

target/i386/gdbstub.c

@@ -18,8 +18,13 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 #include "qemu/osdep.h"
+#include "accel/tcg/vcpu-state.h"
 #include "cpu.h"
+#include "exec/gdbstub.h"
 #include "gdbstub/helpers.h"
+#ifdef CONFIG_LINUX_USER
+#include "linux-user/qemu.h"
+#endif
 
 #ifdef TARGET_X86_64
 static const int gpr_map[16] = {
@@ -406,3 +411,49 @@ int x86_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
     /* Unrecognised register.  */
     return 0;
 }
+
+#ifdef CONFIG_LINUX_USER
+
+#define IDX_ORIG_AX 0
+
+static int x86_cpu_gdb_read_linux_register(CPUState *cs, GByteArray *mem_buf,
+                                           int n)
+{
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+
+    switch (n) {
+    case IDX_ORIG_AX:
+        return gdb_get_reg(env, mem_buf, get_task_state(cs)->orig_ax);
+    }
+    return 0;
+}
+
+static int x86_cpu_gdb_write_linux_register(CPUState *cs, uint8_t *mem_buf,
+                                            int n)
+{
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+
+    switch (n) {
+    case IDX_ORIG_AX:
+        return gdb_write_reg(env, mem_buf, &get_task_state(cs)->orig_ax);
+    }
+    return 0;
+}
+
+#endif
+
+void x86_cpu_gdb_init(CPUState *cs)
+{
+#ifdef CONFIG_LINUX_USER
+    gdb_register_coprocessor(cs, x86_cpu_gdb_read_linux_register,
+                             x86_cpu_gdb_write_linux_register,
+#ifdef TARGET_X86_64
+                             gdb_find_static_feature("i386-64bit-linux.xml"),
+#else
+                             gdb_find_static_feature("i386-32bit-linux.xml"),
+#endif
+                             0);
+#endif
+}