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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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