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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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