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Subject[PATCH 05/27] x86: single_step moved
Date

This moves the single-step support code from ptrace_64.c into a new file
step.c, verbatim. This paves the way for consolidating this code between
64-bit and 32-bit versions.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/x86/kernel/Makefile_64 | 2 +
arch/x86/kernel/ptrace_64.c | 134 -----------------------------------------
arch/x86/kernel/step.c | 140 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 142 insertions(+), 134 deletions(-)
diff --git a/arch/x86/kernel/Makefile_64 b/arch/x86/kernel/Makefile_64
index 203a9d8..d35ee6f 100644
--- a/arch/x86/kernel/Makefile_64
+++ b/arch/x86/kernel/Makefile_64
@@ -13,6 +13,8 @@ obj-y := process_64.o signal_64.o entry_64.o traps_64.o irq_64.o \
pci-dma_64.o pci-nommu_64.o alternative.o hpet.o tsc_64.o bugs_64.o \
i8253.o

+obj-y += step.o
+
obj-$(CONFIG_IA32_EMULATION) += tls.o

obj-$(CONFIG_STACKTRACE) += stacktrace.o
diff --git a/arch/x86/kernel/ptrace_64.c b/arch/x86/kernel/ptrace_64.c
index c2e1a13..52479b1 100644
--- a/arch/x86/kernel/ptrace_64.c
+++ b/arch/x86/kernel/ptrace_64.c
@@ -80,140 +80,6 @@ static inline long put_stack_long(struct task_struct *task, int offset,
return 0;
}

-#define LDT_SEGMENT 4
-
-unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
-{
- unsigned long addr, seg;
-
- addr = regs->rip;
- seg = regs->cs & 0xffff;
-
- /*
- * We'll assume that the code segments in the GDT
- * are all zero-based. That is largely true: the
- * TLS segments are used for data, and the PNPBIOS
- * and APM bios ones we just ignore here.
- */
- if (seg & LDT_SEGMENT) {
- u32 *desc;
- unsigned long base;
-
- seg &= ~7UL;
-
- mutex_lock(&child->mm->context.lock);
- if (unlikely((seg >> 3) >= child->mm->context.size))
- 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));
-
- /* 16-bit code segment? */
- if (!((desc[1] >> 22) & 1))
- addr &= 0xffff;
- addr += base;
- }
- mutex_unlock(&child->mm->context.lock);
- }
-
- return addr;
-}
-
-static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
-{
- int i, copied;
- unsigned char opcode[15];
- unsigned long addr = convert_rip_to_linear(child, regs);
-
- copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
- for (i = 0; i < copied; i++) {
- switch (opcode[i]) {
- /* popf and iret */
- case 0x9d: case 0xcf:
- return 1;
-
- /* CHECKME: 64 65 */
-
- /* opcode and address size prefixes */
- case 0x66: case 0x67:
- continue;
- /* irrelevant prefixes (segment overrides and repeats) */
- case 0x26: case 0x2e:
- case 0x36: case 0x3e:
- case 0x64: case 0x65:
- case 0xf2: case 0xf3:
- continue;
-
- case 0x40 ... 0x4f:
- if (regs->cs != __USER_CS)
- /* 32-bit mode: register increment */
- return 0;
- /* 64-bit mode: REX prefix */
- continue;
-
- /* CHECKME: f2, f3 */
-
- /*
- * pushf: NOTE! We should probably not let
- * the user see the TF bit being set. But
- * it's more pain than it's worth to avoid
- * it, and a debugger could emulate this
- * all in user space if it _really_ cares.
- */
- case 0x9c:
- default:
- return 0;
- }
- }
- return 0;
-}
-
-void user_enable_single_step(struct task_struct *child)
-{
- struct pt_regs *regs = task_pt_regs(child);
-
- /*
- * Always set TIF_SINGLESTEP - this guarantees that
- * we single-step system calls etc.. This will also
- * cause us to set TF when returning to user mode.
- */
- set_tsk_thread_flag(child, TIF_SINGLESTEP);
-
- /*
- * If TF was already set, don't do anything else
- */
- if (regs->eflags & X86_EFLAGS_TF)
- return;
-
- /* Set TF on the kernel stack.. */
- regs->eflags |= 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.
- */
- if (is_setting_trap_flag(child, regs))
- return;
-
- child->ptrace |= PT_DTRACE;
-}
-
-void user_disable_single_step(struct task_struct *child)
-{
- /* Always clear TIF_SINGLESTEP... */
- clear_tsk_thread_flag(child, TIF_SINGLESTEP);
-
- /* But touch TF only if it was set by us.. */
- if (child->ptrace & PT_DTRACE) {
- struct pt_regs *regs = task_pt_regs(child);
- regs->eflags &= ~X86_EFLAGS_TF;
- child->ptrace &= ~PT_DTRACE;
- }
-}
-
/*
* Called by kernel/ptrace.c when detaching..
*
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
new file mode 100644
index 0000000..cb3c8bc
--- /dev/null
+++ b/arch/x86/kernel/step.c
@@ -0,0 +1,140 @@
+/*
+ * x86 single-step support code, common to 32-bit and 64-bit.
+ */
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/ptrace.h>
+
+#define LDT_SEGMENT 4
+
+unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
+{
+ unsigned long addr, seg;
+
+ addr = regs->rip;
+ seg = regs->cs & 0xffff;
+
+ /*
+ * We'll assume that the code segments in the GDT
+ * are all zero-based. That is largely true: the
+ * TLS segments are used for data, and the PNPBIOS
+ * and APM bios ones we just ignore here.
+ */
+ if (seg & LDT_SEGMENT) {
+ u32 *desc;
+ unsigned long base;
+
+ seg &= ~7UL;
+
+ mutex_lock(&child->mm->context.lock);
+ if (unlikely((seg >> 3) >= child->mm->context.size))
+ 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));
+
+ /* 16-bit code segment? */
+ if (!((desc[1] >> 22) & 1))
+ addr &= 0xffff;
+ addr += base;
+ }
+ mutex_unlock(&child->mm->context.lock);
+ }
+
+ return addr;
+}
+
+static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
+{
+ int i, copied;
+ unsigned char opcode[15];
+ unsigned long addr = convert_rip_to_linear(child, regs);
+
+ copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
+ for (i = 0; i < copied; i++) {
+ switch (opcode[i]) {
+ /* popf and iret */
+ case 0x9d: case 0xcf:
+ return 1;
+
+ /* CHECKME: 64 65 */
+
+ /* opcode and address size prefixes */
+ case 0x66: case 0x67:
+ continue;
+ /* irrelevant prefixes (segment overrides and repeats) */
+ case 0x26: case 0x2e:
+ case 0x36: case 0x3e:
+ case 0x64: case 0x65:
+ case 0xf2: case 0xf3:
+ continue;
+
+ case 0x40 ... 0x4f:
+ if (regs->cs != __USER_CS)
+ /* 32-bit mode: register increment */
+ return 0;
+ /* 64-bit mode: REX prefix */
+ continue;
+
+ /* CHECKME: f2, f3 */
+
+ /*
+ * pushf: NOTE! We should probably not let
+ * the user see the TF bit being set. But
+ * it's more pain than it's worth to avoid
+ * it, and a debugger could emulate this
+ * all in user space if it _really_ cares.
+ */
+ case 0x9c:
+ default:
+ return 0;
+ }
+ }
+ return 0;
+}
+
+void user_enable_single_step(struct task_struct *child)
+{
+ struct pt_regs *regs = task_pt_regs(child);
+
+ /*
+ * Always set TIF_SINGLESTEP - this guarantees that
+ * we single-step system calls etc.. This will also
+ * cause us to set TF when returning to user mode.
+ */
+ set_tsk_thread_flag(child, TIF_SINGLESTEP);
+
+ /*
+ * If TF was already set, don't do anything else
+ */
+ if (regs->eflags & X86_EFLAGS_TF)
+ return;
+
+ /* Set TF on the kernel stack.. */
+ regs->eflags |= 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.
+ */
+ if (is_setting_trap_flag(child, regs))
+ return;
+
+ child->ptrace |= PT_DTRACE;
+}
+
+void user_disable_single_step(struct task_struct *child)
+{
+ /* Always clear TIF_SINGLESTEP... */
+ clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+
+ /* But touch TF only if it was set by us.. */
+ if (child->ptrace & PT_DTRACE) {
+ struct pt_regs *regs = task_pt_regs(child);
+ regs->eflags &= ~X86_EFLAGS_TF;
+ child->ptrace &= ~PT_DTRACE;
+ }
+}
-
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