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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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