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    Subject[tip:x86/x32] x32: Add ptrace for x32
    Commit-ID:  55283e2537714f9370c4ab847d170acf223daf90
    Gitweb: http://git.kernel.org/tip/55283e2537714f9370c4ab847d170acf223daf90
    Author: H.J. Lu <hjl.tools@gmail.com>
    AuthorDate: Mon, 5 Mar 2012 15:32:11 -0800
    Committer: H. Peter Anvin <hpa@zytor.com>
    CommitDate: Mon, 5 Mar 2012 15:43:45 -0800

    x32: Add ptrace for x32

    X32 ptrace is a hybrid of 64bit ptrace and compat ptrace with 32bit
    address and longs. It use 64bit ptrace to access the full 64bit
    registers. PTRACE_PEEKUSR and PTRACE_POKEUSR are only allowed to access
    segment and debug registers. PTRACE_PEEKUSR returns the lower 32bits
    and PTRACE_POKEUSR zero-extends 32bit value to 64bit. It works since
    the upper 32bits of segment and debug registers of x32 process are always
    zero. GDB only uses PTRACE_PEEKUSR and PTRACE_POKEUSR to access
    segment and debug registers.

    [ hpa: changed TIF_X32 test to use !is_ia32_task() instead, and moved
    the system call number to the now-unused 521 slot. ]

    Signed-off-by: "H.J. Lu" <hjl.tools@gmail.com>
    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    Cc: Roland McGrath <roland@hack.frob.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Link: http://lkml.kernel.org/r/1329696488-16970-1-git-send-email-hpa@zytor.com
    ---
    arch/x86/kernel/ptrace.c | 99 ++++++++++++++++++++++++++++++++++++++
    arch/x86/syscalls/syscall_64.tbl | 4 +-
    2 files changed, 101 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
    index 5026738..93e7877a 100644
    --- a/arch/x86/kernel/ptrace.c
    +++ b/arch/x86/kernel/ptrace.c
    @@ -1130,6 +1130,100 @@ static int genregs32_set(struct task_struct *target,
    return ret;
    }

    +#ifdef CONFIG_X86_X32_ABI
    +static long x32_arch_ptrace(struct task_struct *child,
    + compat_long_t request, compat_ulong_t caddr,
    + compat_ulong_t cdata)
    +{
    + unsigned long addr = caddr;
    + unsigned long data = cdata;
    + void __user *datap = compat_ptr(data);
    + int ret;
    +
    + switch (request) {
    + /* Read 32bits at location addr in the USER area. Only allow
    + to return the lower 32bits of segment and debug registers. */
    + case PTRACE_PEEKUSR: {
    + u32 tmp;
    +
    + ret = -EIO;
    + if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
    + addr < offsetof(struct user_regs_struct, cs))
    + break;
    +
    + tmp = 0; /* Default return condition */
    + if (addr < sizeof(struct user_regs_struct))
    + tmp = getreg(child, addr);
    + else if (addr >= offsetof(struct user, u_debugreg[0]) &&
    + addr <= offsetof(struct user, u_debugreg[7])) {
    + addr -= offsetof(struct user, u_debugreg[0]);
    + tmp = ptrace_get_debugreg(child, addr / sizeof(data));
    + }
    + ret = put_user(tmp, (__u32 __user *)datap);
    + break;
    + }
    +
    + /* Write the word at location addr in the USER area. Only allow
    + to update segment and debug registers with the upper 32bits
    + zero-extended. */
    + case PTRACE_POKEUSR:
    + ret = -EIO;
    + if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
    + addr < offsetof(struct user_regs_struct, cs))
    + break;
    +
    + if (addr < sizeof(struct user_regs_struct))
    + ret = putreg(child, addr, data);
    + else if (addr >= offsetof(struct user, u_debugreg[0]) &&
    + addr <= offsetof(struct user, u_debugreg[7])) {
    + addr -= offsetof(struct user, u_debugreg[0]);
    + ret = ptrace_set_debugreg(child,
    + addr / sizeof(data), data);
    + }
    + break;
    +
    + case PTRACE_GETREGS: /* Get all gp regs from the child. */
    + return copy_regset_to_user(child,
    + task_user_regset_view(current),
    + REGSET_GENERAL,
    + 0, sizeof(struct user_regs_struct),
    + datap);
    +
    + case PTRACE_SETREGS: /* Set all gp regs in the child. */
    + return copy_regset_from_user(child,
    + task_user_regset_view(current),
    + REGSET_GENERAL,
    + 0, sizeof(struct user_regs_struct),
    + datap);
    +
    + case PTRACE_GETFPREGS: /* Get the child FPU state. */
    + return copy_regset_to_user(child,
    + task_user_regset_view(current),
    + REGSET_FP,
    + 0, sizeof(struct user_i387_struct),
    + datap);
    +
    + case PTRACE_SETFPREGS: /* Set the child FPU state. */
    + return copy_regset_from_user(child,
    + task_user_regset_view(current),
    + REGSET_FP,
    + 0, sizeof(struct user_i387_struct),
    + datap);
    +
    + /* normal 64bit interface to access TLS data.
    + Works just like arch_prctl, except that the arguments
    + are reversed. */
    + case PTRACE_ARCH_PRCTL:
    + return do_arch_prctl(child, data, addr);
    +
    + default:
    + return compat_ptrace_request(child, request, addr, data);
    + }
    +
    + return ret;
    +}
    +#endif
    +
    long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
    compat_ulong_t caddr, compat_ulong_t cdata)
    {
    @@ -1139,6 +1233,11 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
    int ret;
    __u32 val;

    +#ifdef CONFIG_X86_X32_ABI
    + if (!is_ia32_task())
    + return x32_arch_ptrace(child, request, caddr, cdata);
    +#endif
    +
    switch (request) {
    case PTRACE_PEEKUSR:
    ret = getreg32(child, addr, &val);
    diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
    index 0d778b8..dd29a9e 100644
    --- a/arch/x86/syscalls/syscall_64.tbl
    +++ b/arch/x86/syscalls/syscall_64.tbl
    @@ -107,7 +107,7 @@
    98 common getrusage sys_getrusage
    99 common sysinfo sys_sysinfo
    100 common times sys_times
    -101 common ptrace sys_ptrace
    +101 64 ptrace sys_ptrace
    102 common getuid sys_getuid
    103 common syslog sys_syslog
    104 common getgid sys_getgid
    @@ -331,7 +331,7 @@
    518 x32 sendmsg compat_sys_sendmsg
    519 x32 recvmsg compat_sys_recvmsg
    520 x32 execve stub_x32_execve
    -# 521 available
    +521 x32 ptrace compat_sys_ptrace
    522 x32 rt_sigpending sys32_rt_sigpending
    523 x32 rt_sigtimedwait compat_sys_rt_sigtimedwait
    524 x32 rt_sigqueueinfo sys32_rt_sigqueueinfo

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