commit 3674bfadb503e535250730be5df563f0d9928917
author Ilya Leoshkevich <iii@linux.ibm.com> Thu Sep 12 11:28:21 2024 +0200
committer Richard Henderson <richard.henderson@linaro.org> Sun Oct 13 10:05:51 2024 -0700
tree fe82a3e5695df19f733288cffebb9a347de1c1d8
parent f781af3b14fc87c5177d8d8e209d89743e4857df

linux-user/i386: Emulate orig_ax

The kernel uses orig_rax/orig_eax to store the syscall number before
a syscall. One can see this value in core dumps and ptrace.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-ID: <20240912093012.402366-3-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 352960b..6cef8db 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -203,7 +203,7 @@
     (*regs)[12] = tswapreg(env->regs[R_EDX]);
     (*regs)[13] = tswapreg(env->regs[R_ESI]);
     (*regs)[14] = tswapreg(env->regs[R_EDI]);
-    (*regs)[15] = tswapreg(env->regs[R_EAX]); /* XXX */
+    (*regs)[15] = tswapreg(get_task_state(env_cpu_const(env))->orig_ax);
     (*regs)[16] = tswapreg(env->eip);
     (*regs)[17] = tswapreg(env->segs[R_CS].selector & 0xffff);
     (*regs)[18] = tswapreg(env->eflags);
@@ -306,7 +306,7 @@
     (*regs)[8] = tswapreg(env->segs[R_ES].selector & 0xffff);
     (*regs)[9] = tswapreg(env->segs[R_FS].selector & 0xffff);
     (*regs)[10] = tswapreg(env->segs[R_GS].selector & 0xffff);
-    (*regs)[11] = tswapreg(env->regs[R_EAX]); /* XXX */
+    (*regs)[11] = tswapreg(get_task_state(env_cpu_const(env))->orig_ax);
     (*regs)[12] = tswapreg(env->eip);
     (*regs)[13] = tswapreg(env->segs[R_CS].selector & 0xffff);
     (*regs)[14] = tswapreg(env->eflags);

linux-user/i386/cpu_loop.c

diff --git a/linux-user/i386/cpu_loop.c b/linux-user/i386/cpu_loop.c
index 92beb68..7a35215 100644
--- a/linux-user/i386/cpu_loop.c
+++ b/linux-user/i386/cpu_loop.c
@@ -172,6 +172,7 @@
     /*
      * Perform the syscall.  None of the vsyscalls should need restarting.
      */
+    get_task_state(env_cpu(env))->orig_ax = syscall;
     ret = do_syscall(env, syscall, env->regs[R_EDI], env->regs[R_ESI],
                      env->regs[R_EDX], env->regs[10], env->regs[8],
                      env->regs[9], 0, 0);
@@ -221,6 +222,7 @@
         case EXCP_SYSCALL:
 #endif
             /* linux syscall from int $0x80 */
+            get_task_state(cs)->orig_ax = env->regs[R_EAX];
             ret = do_syscall(env,
                              env->regs[R_EAX],
                              env->regs[R_EBX],
@@ -239,6 +241,7 @@
 #ifdef TARGET_X86_64
         case EXCP_SYSCALL:
             /* linux syscall from syscall instruction.  */
+            get_task_state(cs)->orig_ax = env->regs[R_EAX];
             ret = do_syscall(env,
                              env->regs[R_EAX],
                              env->regs[R_EDI],

linux-user/qemu.h

diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 98ad848..895bdd7 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -114,6 +114,10 @@
     uint32_t v86flags;
     uint32_t v86mask;
 #endif
+#if defined(TARGET_I386)
+    /* Last syscall number. */
+    target_ulong orig_ax;
+#endif
     abi_ulong child_tidptr;
 #ifdef TARGET_M68K
     abi_ulong tp_value;