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Subject[PATCH 08/27] x86: single_step: share code
Date

This removes the single-step code from ptrace_32.c and uses the step.c code
shared with the 64-bit kernel. The two versions of the code were nearly
identical already, so the shared code has only a couple of simple #ifdef's.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/x86/kernel/Makefile_32 | 1 +
arch/x86/kernel/ptrace_32.c | 125 -------------------------------------------
arch/x86/kernel/step.c | 14 +++++
3 files changed, 15 insertions(+), 125 deletions(-)
diff --git a/arch/x86/kernel/Makefile_32 b/arch/x86/kernel/Makefile_32
index e660584..959ad3c 100644
--- a/arch/x86/kernel/Makefile_32
+++ b/arch/x86/kernel/Makefile_32
@@ -11,6 +11,7 @@ obj-y := process_32.o signal_32.o entry_32.o traps_32.o irq_32.o \
quirks.o i8237.o topology.o alternative.o i8253.o tsc_32.o

obj-y += tls.o
+obj-y += step.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += cpu/
obj-y += acpi/
diff --git a/arch/x86/kernel/ptrace_32.c b/arch/x86/kernel/ptrace_32.c
index d1d74e1..e599db5 100644
--- a/arch/x86/kernel/ptrace_32.c
+++ b/arch/x86/kernel/ptrace_32.c
@@ -137,131 +137,6 @@ static unsigned long getreg(struct task_struct *child,
return retval;
}

-#define LDT_SEGMENT 4
-
-static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
-{
- unsigned long addr, seg;
-
- addr = regs->eip;
- seg = regs->xcs & 0xffff;
- if (regs->eflags & VM_MASK) {
- addr = (addr & 0xffff) + (seg << 4);
- return addr;
- }
-
- /*
- * 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 inline int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
-{
- int i, copied;
- unsigned char opcode[15];
- unsigned long addr = convert_eip_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;
- /* 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 0xf0: case 0xf2: case 0xf3:
- continue;
-
- /*
- * 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 = get_child_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 = get_child_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
index 6a93b93..6732272 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -5,12 +5,24 @@
#include <linux/mm.h>
#include <linux/ptrace.h>

+#ifdef CONFIG_X86_32
+static
+#endif
unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
{
unsigned long addr, seg;

+#ifdef CONFIG_X86_64
addr = regs->rip;
seg = regs->cs & 0xffff;
+#else
+ addr = regs->eip;
+ seg = regs->xcs & 0xffff;
+ if (regs->eflags & X86_EFLAGS_VM) {
+ addr = (addr & 0xffff) + (seg << 4);
+ return addr;
+ }
+#endif

/*
* We'll assume that the code segments in the GDT
@@ -69,12 +81,14 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
case 0xf0: case 0xf2: case 0xf3:
continue;

+#ifdef CONFIG_X86_64
case 0x40 ... 0x4f:
if (regs->cs != __USER_CS)
/* 32-bit mode: register increment */
return 0;
/* 64-bit mode: REX prefix */
continue;
+#endif

/* CHECKME: f2, f3 */

-
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