Commit 864232fa authored by Will Deacon's avatar Will Deacon Committed by Russell King
Browse files

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: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f81ef4a9
......@@ -2,6 +2,11 @@
#define _ARM_HW_BREAKPOINT_H
#ifdef __KERNEL__
struct task_struct;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
struct arch_hw_breakpoint_ctrl {
u32 __reserved : 9,
mismatch : 1,
......@@ -102,7 +107,6 @@ static inline void decode_ctrl_reg(u32 reg,
struct notifier_block;
struct perf_event;
struct pmu;
struct task_struct;
extern struct pmu perf_ops_bp;
extern int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
......@@ -111,13 +115,19 @@ extern int arch_check_bp_in_kernelspace(struct perf_event *bp);
extern int arch_validate_hwbkpt_settings(struct perf_event *bp);
extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
unsigned long val, void *data);
extern u8 arch_get_debug_arch(void);
extern u8 arch_get_max_wp_len(void);
extern void clear_ptrace_hw_breakpoint(struct task_struct *tsk);
int arch_install_hw_breakpoint(struct perf_event *bp);
void arch_uninstall_hw_breakpoint(struct perf_event *bp);
void hw_breakpoint_pmu_read(struct perf_event *bp);
int hw_breakpoint_slots(int type);
#else
static inline void clear_ptrace_hw_breakpoint(struct task_struct *tsk) {}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* __KERNEL__ */
#endif /* _ARM_HW_BREAKPOINT_H */
......@@ -19,6 +19,7 @@
#ifdef __KERNEL__
#include <asm/hw_breakpoint.h>
#include <asm/ptrace.h>
#include <asm/types.h>
......@@ -41,6 +42,9 @@ struct debug_entry {
struct debug_info {
int nsaved;
struct debug_entry bp[2];
#ifdef CONFIG_HAVE_HW_BREAKPOINT
struct perf_event *hbp[ARM_MAX_HBP_SLOTS];
#endif
};
struct thread_struct {
......
......@@ -29,6 +29,8 @@
#define PTRACE_SETCRUNCHREGS 26
#define PTRACE_GETVFPREGS 27
#define PTRACE_SETVFPREGS 28
#define PTRACE_GETHBPREGS 29
#define PTRACE_SETHBPREGS 30
/*
* PSR bits
......
......@@ -29,6 +29,7 @@
#include <linux/utsname.h>
#include <linux/uaccess.h>
#include <linux/random.h>
#include <linux/hw_breakpoint.h>
#include <asm/cacheflush.h>
#include <asm/leds.h>
......@@ -317,6 +318,8 @@ void flush_thread(void)
struct thread_info *thread = current_thread_info();
struct task_struct *tsk = current;
flush_ptrace_hw_breakpoint(tsk);
memset(thread->used_cp, 0, sizeof(thread->used_cp));
memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
memset(&thread->fpstate, 0, sizeof(union fp_state));
......@@ -345,6 +348,8 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start,
thread->cpu_context.sp = (unsigned long)childregs;
thread->cpu_context.pc = (unsigned long)ret_from_fork;
clear_ptrace_hw_breakpoint(p);
if (clone_flags & CLONE_SETTLS)
thread->tp_value = regs->ARM_r3;
......
......@@ -19,6 +19,8 @@
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <asm/pgtable.h>
#include <asm/system.h>
......@@ -847,6 +849,232 @@ static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
}
#endif
#ifdef CONFIG_HAVE_HW_BREAKPOINT
/*
* Convert a virtual register number into an index for a thread_info
* breakpoint array. Breakpoints are identified using positive numbers
* whilst watchpoints are negative. The registers are laid out as pairs
* of (address, control), each pair mapping to a unique hw_breakpoint struct.
* Register 0 is reserved for describing resource information.
*/
static int ptrace_hbp_num_to_idx(long num)
{
if (num < 0)
num = (ARM_MAX_BRP << 1) - num;
return (num - 1) >> 1;
}
/*
* Returns the virtual register number for the address of the
* breakpoint at index idx.
*/
static long ptrace_hbp_idx_to_num(int idx)
{
long mid = ARM_MAX_BRP << 1;
long num = (idx << 1) + 1;
return num > mid ? mid - num : num;
}
/*
* Handle hitting a HW-breakpoint.
*/
static void ptrace_hbptriggered(struct perf_event *bp, int unused,
struct perf_sample_data *data,
struct pt_regs *regs)
{
struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
long num;
int i;
siginfo_t info;
for (i = 0; i < ARM_MAX_HBP_SLOTS; ++i)
if (current->thread.debug.hbp[i] == bp)
break;
num = (i == ARM_MAX_HBP_SLOTS) ? 0 : ptrace_hbp_idx_to_num(i);
info.si_signo = SIGTRAP;
info.si_errno = (int)num;
info.si_code = TRAP_HWBKPT;
info.si_addr = (void __user *)(bkpt->trigger);
force_sig_info(SIGTRAP, &info, current);
}
/*
* Set ptrace breakpoint pointers to zero for this task.
* This is required in order to prevent child processes from unregistering
* breakpoints held by their parent.
*/
void clear_ptrace_hw_breakpoint(struct task_struct *tsk)
{
memset(tsk->thread.debug.hbp, 0, sizeof(tsk->thread.debug.hbp));
}
/*
* Unregister breakpoints from this task and reset the pointers in
* the thread_struct.
*/
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
int i;
struct thread_struct *t = &tsk->thread;
for (i = 0; i < ARM_MAX_HBP_SLOTS; i++) {
if (t->debug.hbp[i]) {
unregister_hw_breakpoint(t->debug.hbp[i]);
t->debug.hbp[i] = NULL;
}
}
}
static u32 ptrace_get_hbp_resource_info(void)
{
u8 num_brps, num_wrps, debug_arch, wp_len;
u32 reg = 0;
num_brps = hw_breakpoint_slots(TYPE_INST);
num_wrps = hw_breakpoint_slots(TYPE_DATA);
debug_arch = arch_get_debug_arch();
wp_len = arch_get_max_wp_len();
reg |= debug_arch;
reg <<= 8;
reg |= wp_len;
reg <<= 8;
reg |= num_wrps;
reg <<= 8;
reg |= num_brps;
return reg;
}
static struct perf_event *ptrace_hbp_create(struct task_struct *tsk, int type)
{
struct perf_event_attr attr;
ptrace_breakpoint_init(&attr);
/* Initialise fields to sane defaults. */
attr.bp_addr = 0;
attr.bp_len = HW_BREAKPOINT_LEN_4;
attr.bp_type = type;
attr.disabled = 1;
return register_user_hw_breakpoint(&attr, ptrace_hbptriggered, tsk);
}
static int ptrace_gethbpregs(struct task_struct *tsk, long num,
unsigned long __user *data)
{
u32 reg;
int idx, ret = 0;
struct perf_event *bp;
struct arch_hw_breakpoint_ctrl arch_ctrl;
if (num == 0) {
reg = ptrace_get_hbp_resource_info();
} else {
idx = ptrace_hbp_num_to_idx(num);
if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
ret = -EINVAL;
goto out;
}
bp = tsk->thread.debug.hbp[idx];
if (!bp) {
reg = 0;
goto put;
}
arch_ctrl = counter_arch_bp(bp)->ctrl;
/*
* Fix up the len because we may have adjusted it
* to compensate for an unaligned address.
*/
while (!(arch_ctrl.len & 0x1))
arch_ctrl.len >>= 1;
if (idx & 0x1)
reg = encode_ctrl_reg(arch_ctrl);
else
reg = bp->attr.bp_addr;
}
put:
if (put_user(reg, data))
ret = -EFAULT;
out:
return ret;
}
static int ptrace_sethbpregs(struct task_struct *tsk, long num,
unsigned long __user *data)
{
int idx, gen_len, gen_type, implied_type, ret = 0;
u32 user_val;
struct perf_event *bp;
struct arch_hw_breakpoint_ctrl ctrl;
struct perf_event_attr attr;
if (num == 0)
goto out;
else if (num < 0)
implied_type = HW_BREAKPOINT_RW;
else
implied_type = HW_BREAKPOINT_X;
idx = ptrace_hbp_num_to_idx(num);
if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
ret = -EINVAL;
goto out;
}
if (get_user(user_val, data)) {
ret = -EFAULT;
goto out;
}
bp = tsk->thread.debug.hbp[idx];
if (!bp) {
bp = ptrace_hbp_create(tsk, implied_type);
if (IS_ERR(bp)) {
ret = PTR_ERR(bp);
goto out;
}
tsk->thread.debug.hbp[idx] = bp;
}
attr = bp->attr;
if (num & 0x1) {
/* Address */
attr.bp_addr = user_val;
} else {
/* Control */
decode_ctrl_reg(user_val, &ctrl);
ret = arch_bp_generic_fields(ctrl, &gen_len, &gen_type);
if (ret)
goto out;
if ((gen_type & implied_type) != gen_type) {
ret = -EINVAL;
goto out;
}
attr.bp_len = gen_len;
attr.bp_type = gen_type;
attr.disabled = !ctrl.enabled;
}
ret = modify_user_hw_breakpoint(bp, &attr);
out:
return ret;
}
#endif
long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
int ret;
......@@ -916,6 +1144,17 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
break;
#endif
#ifdef CONFIG_HAVE_HW_BREAKPOINT
case PTRACE_GETHBPREGS:
ret = ptrace_gethbpregs(child, addr,
(unsigned long __user *)data);
break;
case PTRACE_SETHBPREGS:
ret = ptrace_sethbpregs(child, addr,
(unsigned long __user *)data);
break;
#endif
default:
ret = ptrace_request(child, request, addr, data);
break;
......
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