#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
+#include <asm/desc.h>
-#ifdef CONFIG_X86_32
-static
-#endif
-unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
+unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs)
{
unsigned long addr, seg;
-#ifdef CONFIG_X86_64
- addr = regs->rip;
+ addr = regs->ip;
seg = regs->cs & 0xffff;
-#else
- addr = regs->eip;
- seg = regs->xcs & 0xffff;
- if (regs->eflags & X86_EFLAGS_VM) {
+ if (v8086_mode(regs)) {
addr = (addr & 0xffff) + (seg << 4);
return addr;
}
-#endif
/*
* We'll assume that the code segments in the GDT
* and APM bios ones we just ignore here.
*/
if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) {
- u32 *desc;
+ struct desc_struct *desc;
unsigned long base;
seg &= ~7UL;
addr = -1L; /* bogus selector, access would fault */
else {
desc = child->mm->context.ldt + seg;
- base = ((desc[0] >> 16) |
- ((desc[1] & 0xff) << 16) |
- (desc[1] & 0xff000000));
+ base = get_desc_base(desc);
/* 16-bit code segment? */
- if (!((desc[1] >> 22) & 1))
+ if (!desc->d)
addr &= 0xffff;
addr += base;
}
{
int i, copied;
unsigned char opcode[15];
- unsigned long addr = convert_rip_to_linear(child, regs);
+ unsigned long addr = convert_ip_to_linear(child, regs);
copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
for (i = 0; i < copied; i++) {
#ifdef CONFIG_X86_64
case 0x40 ... 0x4f:
- if (regs->cs != __USER_CS)
+ if (!user_64bit_mode(regs))
/* 32-bit mode: register increment */
return 0;
/* 64-bit mode: REX prefix */
static int enable_single_step(struct task_struct *child)
{
struct pt_regs *regs = task_pt_regs(child);
+ unsigned long oflags;
+
+ /*
+ * If we stepped into a sysenter/syscall insn, it trapped in
+ * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.
+ * If user-mode had set TF itself, then it's still clear from
+ * do_debug() and we need to set it again to restore the user
+ * state so we don't wrongly set TIF_FORCED_TF below.
+ * If enable_single_step() was used last and that is what
+ * set TIF_SINGLESTEP, then both TF and TIF_FORCED_TF are
+ * already set and our bookkeeping is fine.
+ */
+ if (unlikely(test_tsk_thread_flag(child, TIF_SINGLESTEP)))
+ regs->flags |= X86_EFLAGS_TF;
/*
* Always set TIF_SINGLESTEP - this guarantees that
*/
set_tsk_thread_flag(child, TIF_SINGLESTEP);
- /*
- * If TF was already set, don't do anything else
- */
- if (regs->eflags & X86_EFLAGS_TF)
- return 0;
+ oflags = regs->flags;
/* Set TF on the kernel stack.. */
- regs->eflags |= X86_EFLAGS_TF;
+ regs->flags |= X86_EFLAGS_TF;
/*
* ..but if TF is changed by the instruction we will trace,
* don't mark it as being "us" that set it, so that we
* won't clear it by hand later.
+ *
+ * Note that if we don't actually execute the popf because
+ * of a signal arriving right now or suchlike, we will lose
+ * track of the fact that it really was "us" that set it.
*/
- if (is_setting_trap_flag(child, regs))
+ if (is_setting_trap_flag(child, regs)) {
+ clear_tsk_thread_flag(child, TIF_FORCED_TF);
return 0;
+ }
+
+ /*
+ * If TF was already set, check whether it was us who set it.
+ * If not, we should never attempt a block step.
+ */
+ if (oflags & X86_EFLAGS_TF)
+ return test_tsk_thread_flag(child, TIF_FORCED_TF);
set_tsk_thread_flag(child, TIF_FORCED_TF);
return 1;
}
-/*
- * Install this value in MSR_IA32_DEBUGCTLMSR whenever child is running.
- */
-static void write_debugctlmsr(struct task_struct *child, unsigned long val)
+void set_task_blockstep(struct task_struct *task, bool on)
{
- child->thread.debugctlmsr = val;
-
- if (child != current)
- return;
+ unsigned long debugctl;
-#ifdef CONFIG_X86_64
- wrmsrl(MSR_IA32_DEBUGCTLMSR, val);
-#else
- wrmsr(MSR_IA32_DEBUGCTLMSR, val, 0);
-#endif
+ /*
+ * Ensure irq/preemption can't change debugctl in between.
+ * Note also that both TIF_BLOCKSTEP and debugctl should
+ * be changed atomically wrt preemption.
+ *
+ * NOTE: this means that set/clear TIF_BLOCKSTEP is only safe if
+ * task is current or it can't be running, otherwise we can race
+ * with __switch_to_xtra(). We rely on ptrace_freeze_traced() but
+ * PTRACE_KILL is not safe.
+ */
+ local_irq_disable();
+ debugctl = get_debugctlmsr();
+ if (on) {
+ debugctl |= DEBUGCTLMSR_BTF;
+ set_tsk_thread_flag(task, TIF_BLOCKSTEP);
+ } else {
+ debugctl &= ~DEBUGCTLMSR_BTF;
+ clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
+ }
+ if (task == current)
+ update_debugctlmsr(debugctl);
+ local_irq_enable();
}
/*
* Make sure block stepping (BTF) is not enabled unless it should be.
* Note that we don't try to worry about any is_setting_trap_flag()
* instructions after the first when using block stepping.
- * So noone should try to use debugger block stepping in a program
+ * So no one should try to use debugger block stepping in a program
* that uses user-mode single stepping itself.
*/
- if (enable_single_step(child) && block) {
- set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
- write_debugctlmsr(child, DEBUGCTLMSR_BTF);
- } else if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR)) {
- write_debugctlmsr(child, 0);
- }
+ if (enable_single_step(child) && block)
+ set_task_blockstep(child, true);
+ else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
+ set_task_blockstep(child, false);
}
void user_enable_single_step(struct task_struct *child)
/*
* Make sure block stepping (BTF) is disabled.
*/
- if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR))
- write_debugctlmsr(child, 0);
+ if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
+ set_task_blockstep(child, false);
/* Always clear TIF_SINGLESTEP... */
clear_tsk_thread_flag(child, TIF_SINGLESTEP);
/* But touch TF only if it was set by us.. */
if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))
- task_pt_regs(child)->eflags &= ~X86_EFLAGS_TF;
+ task_pt_regs(child)->flags &= ~X86_EFLAGS_TF;
}