This fix two related bugs:
* PTRACE_GETREGS doesn't get the right orig_ax (syscall) value
* PTRACE_SETREGS can't set the orig_ax value (erased by initial value)

Remove the now useless and error-prone get_syscall().

Signed-off-by: Mickaël Salaün <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Will Drewry <[email protected]>
Cc: Thomas Meyer <[email protected]>
Cc: Nicolas Iooss <[email protected]>
Cc: Anton Ivanov <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Meredydd Luff <[email protected]>
Cc: David Drysdale <[email protected]>
---
 arch/um/kernel/skas/syscall.c   | 7 ++++++-
 arch/um/os-Linux/skas/process.c | 7 -------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 1683b8e..65f0d1a 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -7,6 +7,7 @@
 #include <linux/ptrace.h>
 #include <kern_util.h>
 #include <sysdep/ptrace.h>
+#include <sysdep/ptrace_user.h>
 #include <sysdep/syscalls.h>
 #include <os.h>
 
@@ -16,12 +17,16 @@ void handle_syscall(struct uml_pt_regs *r)
        long result;
        int syscall;
 
+       /* Save the syscall register. */
+       UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
+
        if (syscall_trace_enter(regs)) {
                result = -ENOSYS;
                goto out;
        }
 
-       syscall = get_syscall(r);
+       /* Get the syscall after being potentially updated with ptrace. */
+       syscall = UPT_SYSCALL_NR(r);
 
        if ((syscall > __NR_syscall_max) || syscall < 0)
                result = -ENOSYS;
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index b856c66..23025d6 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -172,13 +172,6 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
        handle_syscall(regs);
 }
 
-int get_syscall(struct uml_pt_regs *regs)
-{
-       UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
-
-       return UPT_SYSCALL_NR(regs);
-}
-
 extern char __syscall_stub_start[];
 
 static int userspace_tramp(void *stack)
-- 
2.6.4

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