ARM: 6357/1: hw-breakpoint: add new ptrace requests for hw-breakpoint interaction
For debuggers to take advantage of the hw-breakpoint framework in the kernel, it is necessary to expose the API calls via a ptrace interface. This patch exposes the hardware breakpoints framework as a collection of virtual registers, accesible using PTRACE_SETHBPREGS and PTRACE_GETHBPREGS requests. The breakpoints are stored in the debug_info struct of the running thread. Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: S. Karthikeyan <informkarthik@gmail.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon
committed by
Russell King
Russell King
parent
f81ef4a920
commit
864232fa1a
@@ -19,6 +19,8 @@
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#include <linux/init.h>
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#include <linux/signal.h>
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#include <linux/uaccess.h>
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#include <linux/perf_event.h>
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#include <linux/hw_breakpoint.h>
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#include <asm/pgtable.h>
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#include <asm/system.h>
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@@ -847,6 +849,232 @@ static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
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}
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#endif
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#ifdef CONFIG_HAVE_HW_BREAKPOINT
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/*
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* Convert a virtual register number into an index for a thread_info
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* breakpoint array. Breakpoints are identified using positive numbers
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* whilst watchpoints are negative. The registers are laid out as pairs
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* of (address, control), each pair mapping to a unique hw_breakpoint struct.
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* Register 0 is reserved for describing resource information.
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*/
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static int ptrace_hbp_num_to_idx(long num)
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{
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if (num < 0)
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num = (ARM_MAX_BRP << 1) - num;
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return (num - 1) >> 1;
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}
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/*
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* Returns the virtual register number for the address of the
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* breakpoint at index idx.
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*/
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static long ptrace_hbp_idx_to_num(int idx)
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{
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long mid = ARM_MAX_BRP << 1;
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long num = (idx << 1) + 1;
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return num > mid ? mid - num : num;
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}
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/*
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* Handle hitting a HW-breakpoint.
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*/
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static void ptrace_hbptriggered(struct perf_event *bp, int unused,
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struct perf_sample_data *data,
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struct pt_regs *regs)
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{
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struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
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long num;
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int i;
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siginfo_t info;
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for (i = 0; i < ARM_MAX_HBP_SLOTS; ++i)
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if (current->thread.debug.hbp[i] == bp)
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break;
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num = (i == ARM_MAX_HBP_SLOTS) ? 0 : ptrace_hbp_idx_to_num(i);
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info.si_signo = SIGTRAP;
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info.si_errno = (int)num;
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info.si_code = TRAP_HWBKPT;
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info.si_addr = (void __user *)(bkpt->trigger);
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force_sig_info(SIGTRAP, &info, current);
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}
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/*
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* Set ptrace breakpoint pointers to zero for this task.
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* This is required in order to prevent child processes from unregistering
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* breakpoints held by their parent.
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*/
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void clear_ptrace_hw_breakpoint(struct task_struct *tsk)
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{
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memset(tsk->thread.debug.hbp, 0, sizeof(tsk->thread.debug.hbp));
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}
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/*
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* Unregister breakpoints from this task and reset the pointers in
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* the thread_struct.
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*/
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void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
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{
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int i;
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struct thread_struct *t = &tsk->thread;
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for (i = 0; i < ARM_MAX_HBP_SLOTS; i++) {
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if (t->debug.hbp[i]) {
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unregister_hw_breakpoint(t->debug.hbp[i]);
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t->debug.hbp[i] = NULL;
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}
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}
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}
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static u32 ptrace_get_hbp_resource_info(void)
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{
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u8 num_brps, num_wrps, debug_arch, wp_len;
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u32 reg = 0;
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num_brps = hw_breakpoint_slots(TYPE_INST);
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num_wrps = hw_breakpoint_slots(TYPE_DATA);
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debug_arch = arch_get_debug_arch();
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wp_len = arch_get_max_wp_len();
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reg |= debug_arch;
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reg <<= 8;
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reg |= wp_len;
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reg <<= 8;
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reg |= num_wrps;
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reg <<= 8;
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reg |= num_brps;
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return reg;
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}
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static struct perf_event *ptrace_hbp_create(struct task_struct *tsk, int type)
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{
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struct perf_event_attr attr;
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ptrace_breakpoint_init(&attr);
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/* Initialise fields to sane defaults. */
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attr.bp_addr = 0;
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attr.bp_len = HW_BREAKPOINT_LEN_4;
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attr.bp_type = type;
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attr.disabled = 1;
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return register_user_hw_breakpoint(&attr, ptrace_hbptriggered, tsk);
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}
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static int ptrace_gethbpregs(struct task_struct *tsk, long num,
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unsigned long __user *data)
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{
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u32 reg;
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int idx, ret = 0;
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struct perf_event *bp;
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struct arch_hw_breakpoint_ctrl arch_ctrl;
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if (num == 0) {
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reg = ptrace_get_hbp_resource_info();
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} else {
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idx = ptrace_hbp_num_to_idx(num);
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if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
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ret = -EINVAL;
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goto out;
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}
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bp = tsk->thread.debug.hbp[idx];
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if (!bp) {
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reg = 0;
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goto put;
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}
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arch_ctrl = counter_arch_bp(bp)->ctrl;
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/*
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* Fix up the len because we may have adjusted it
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* to compensate for an unaligned address.
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*/
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while (!(arch_ctrl.len & 0x1))
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arch_ctrl.len >>= 1;
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if (idx & 0x1)
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reg = encode_ctrl_reg(arch_ctrl);
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else
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reg = bp->attr.bp_addr;
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}
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put:
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if (put_user(reg, data))
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ret = -EFAULT;
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out:
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return ret;
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}
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static int ptrace_sethbpregs(struct task_struct *tsk, long num,
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unsigned long __user *data)
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{
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int idx, gen_len, gen_type, implied_type, ret = 0;
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u32 user_val;
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struct perf_event *bp;
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struct arch_hw_breakpoint_ctrl ctrl;
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struct perf_event_attr attr;
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if (num == 0)
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goto out;
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else if (num < 0)
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implied_type = HW_BREAKPOINT_RW;
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else
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implied_type = HW_BREAKPOINT_X;
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idx = ptrace_hbp_num_to_idx(num);
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if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
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ret = -EINVAL;
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goto out;
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}
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if (get_user(user_val, data)) {
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ret = -EFAULT;
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goto out;
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}
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bp = tsk->thread.debug.hbp[idx];
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if (!bp) {
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bp = ptrace_hbp_create(tsk, implied_type);
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if (IS_ERR(bp)) {
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ret = PTR_ERR(bp);
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goto out;
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}
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tsk->thread.debug.hbp[idx] = bp;
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}
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attr = bp->attr;
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if (num & 0x1) {
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/* Address */
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attr.bp_addr = user_val;
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} else {
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/* Control */
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decode_ctrl_reg(user_val, &ctrl);
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ret = arch_bp_generic_fields(ctrl, &gen_len, &gen_type);
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if (ret)
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goto out;
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if ((gen_type & implied_type) != gen_type) {
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ret = -EINVAL;
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goto out;
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}
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attr.bp_len = gen_len;
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attr.bp_type = gen_type;
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attr.disabled = !ctrl.enabled;
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}
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ret = modify_user_hw_breakpoint(bp, &attr);
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out:
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return ret;
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}
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#endif
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long arch_ptrace(struct task_struct *child, long request, long addr, long data)
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{
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int ret;
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@@ -916,6 +1144,17 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
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break;
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#endif
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#ifdef CONFIG_HAVE_HW_BREAKPOINT
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case PTRACE_GETHBPREGS:
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ret = ptrace_gethbpregs(child, addr,
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(unsigned long __user *)data);
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break;
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case PTRACE_SETHBPREGS:
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ret = ptrace_sethbpregs(child, addr,
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(unsigned long __user *)data);
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break;
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#endif
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default:
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ret = ptrace_request(child, request, addr, data);
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break;
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