Re: [PATCH v3 3/3] Powerpc64/Watchpoint: Rewrite ptrace-hwbreak.c selftest

[Christophe Leroy]

Le 10/07/2019 Ã 06:54, Ravi Bangoria a ÃcritÂ:
> ptrace-hwbreak.c selftest is logically broken. On powerpc, when
> watchpoint is created with ptrace, signals are generated before
> executing the instruction and user has to manually singlestep
> the instruction with watchpoint disabled, which selftest never
> does and thus it keeps on getting the signal at the same
> instruction. If we fix it, selftest fails because the logical
> connection between tracer(parent) and tracee(child) is also
> broken. Rewrite the selftest and add new tests for unaligned
> access.

On the 8xx, signals are generated after executing the instruction.

Can we make the test work in both case ?

Christophe

> With patch:
>    $ ./tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak
>    test: ptrace-hwbreak
>    tags: git_version:v5.2-rc2-33-ga247a75f90a9-dirty
>    PTRACE_SET_DEBUGREG, WO, len: 1: Ok
>    PTRACE_SET_DEBUGREG, WO, len: 2: Ok
>    PTRACE_SET_DEBUGREG, WO, len: 4: Ok
>    PTRACE_SET_DEBUGREG, WO, len: 8: Ok
>    PTRACE_SET_DEBUGREG, RO, len: 1: Ok
>    PTRACE_SET_DEBUGREG, RO, len: 2: Ok
>    PTRACE_SET_DEBUGREG, RO, len: 4: Ok
>    PTRACE_SET_DEBUGREG, RO, len: 8: Ok
>    PTRACE_SET_DEBUGREG, RW, len: 1: Ok
>    PTRACE_SET_DEBUGREG, RW, len: 2: Ok
>    PTRACE_SET_DEBUGREG, RW, len: 4: Ok
>    PTRACE_SET_DEBUGREG, RW, len: 8: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_EXACT, WO, len: 1: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RO, len: 1: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RW, len: 1: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, WO, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, RO, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, RW, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW UNALIGNED, WO, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW UNALIGNED, RO, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW UNALIGNED, RW, len: 6: Ok
>    PPC_PTRACE_SETHWDEBUG, DAWR_MAX_LEN, RW, len: 512: Ok
>    success: ptrace-hwbreak
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> ---
>   .../selftests/powerpc/ptrace/ptrace-hwbreak.c | 535 +++++++++++-------
>   1 file changed, 325 insertions(+), 210 deletions(-)
>
> diff --git a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> index 3066d310f32b..fb1e05d7f77c 100644
> --- a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> +++ b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> @@ -22,318 +22,433 @@
>   #include <sys/wait.h>
>   #include "ptrace.h"
>   
> -/* Breakpoint access modes */
> -enum {
> -	BP_X = 1,
> -	BP_RW = 2,
> -	BP_W = 4,
> -};
> -
> -static pid_t child_pid;
> -static struct ppc_debug_info dbginfo;
> -
> -static void get_dbginfo(void)
> -{
> -	int ret;
> -
> -	ret = ptrace(PPC_PTRACE_GETHWDBGINFO, child_pid, NULL, &dbginfo);
> -	if (ret) {
> -		perror("Can't get breakpoint info\n");
> -		exit(-1);
> -	}
> -}
> -
> -static bool hwbreak_present(void)
> -{
> -	return (dbginfo.num_data_bps != 0);
> -}
> +/*
> + * Use volatile on all global var so that compiler doesn't
> + * optimise their load/stores. Otherwise selftest can fail.
> + */
> +static volatile __u64 glvar;
>   
> -static bool dawr_present(void)
> -{
> -	return !!(dbginfo.features & PPC_DEBUG_FEATURE_DATA_BP_DAWR);
> -}
> +#define DAWR_MAX_LEN 512
> +static volatile __u8 big_var[DAWR_MAX_LEN] __attribute__((aligned(512)));
>   
> -static void set_breakpoint_addr(void *addr)
> -{
> -	int ret;
> +#define A_LEN 6
> +#define B_LEN 6
> +struct gstruct {
> +	__u8 a[A_LEN]; /* double word aligned */
> +	__u8 b[B_LEN]; /* double word unaligned */
> +};
> +static volatile struct gstruct gstruct __attribute__((aligned(512)));
>   
> -	ret = ptrace(PTRACE_SET_DEBUGREG, child_pid, 0, addr);
> -	if (ret) {
> -		perror("Can't set breakpoint addr\n");
> -		exit(-1);
> -	}
> -}
>   
> -static int set_hwbreakpoint_addr(void *addr, int range)
> +static void get_dbginfo(pid_t child_pid, struct ppc_debug_info *dbginfo)
>   {
> -	int ret;
> -
> -	struct ppc_hw_breakpoint info;
> -
> -	info.version = 1;
> -	info.trigger_type = PPC_BREAKPOINT_TRIGGER_RW;
> -	info.addr_mode = PPC_BREAKPOINT_MODE_EXACT;
> -	if (range > 0)
> -		info.addr_mode = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
> -	info.condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
> -	info.addr = (__u64)addr;
> -	info.addr2 = (__u64)addr + range;
> -	info.condition_value = 0;
> -
> -	ret = ptrace(PPC_PTRACE_SETHWDEBUG, child_pid, 0, &info);
> -	if (ret < 0) {
> -		perror("Can't set breakpoint\n");
> +	if (ptrace(PPC_PTRACE_GETHWDBGINFO, child_pid, NULL, dbginfo)) {
> +		perror("Can't get breakpoint info");
>   		exit(-1);
>   	}
> -	return ret;
>   }
>   
> -static int del_hwbreakpoint_addr(int watchpoint_handle)
> +static bool dawr_present(struct ppc_debug_info *dbginfo)
>   {
> -	int ret;
> -
> -	ret = ptrace(PPC_PTRACE_DELHWDEBUG, child_pid, 0, watchpoint_handle);
> -	if (ret < 0) {
> -		perror("Can't delete hw breakpoint\n");
> -		exit(-1);
> -	}
> -	return ret;
> +	return !!(dbginfo->features & PPC_DEBUG_FEATURE_DATA_BP_DAWR);
>   }
>   
> -#define DAWR_LENGTH_MAX 512
> -
> -/* Dummy variables to test read/write accesses */
> -static unsigned long long
> -	dummy_array[DAWR_LENGTH_MAX / sizeof(unsigned long long)]
> -	__attribute__((aligned(512)));
> -static unsigned long long *dummy_var = dummy_array;
> -
>   static void write_var(int len)
>   {
> -	long long *plval;
> -	char *pcval;
> -	short *psval;
> -	int *pival;
> +	__u8 *pcvar;
> +	__u16 *psvar;
> +	__u32 *pivar;
> +	__u64 *plvar;
>   
>   	switch (len) {
>   	case 1:
> -		pcval = (char *)dummy_var;
> -		*pcval = 0xff;
> +		pcvar = (__u8 *)&glvar;
> +		*pcvar = 0xff;
>   		break;
>   	case 2:
> -		psval = (short *)dummy_var;
> -		*psval = 0xffff;
> +		psvar = (__u16 *)&glvar;
> +		*psvar = 0xffff;
>   		break;
>   	case 4:
> -		pival = (int *)dummy_var;
> -		*pival = 0xffffffff;
> +		pivar = (__u32 *)&glvar;
> +		*pivar = 0xffffffff;
>   		break;
>   	case 8:
> -		plval = (long long *)dummy_var;
> -		*plval = 0xffffffffffffffffLL;
> +		plvar = (__u64 *)&glvar;
> +		*plvar = 0xffffffffffffffffLL;
>   		break;
>   	}
>   }
>   
>   static void read_var(int len)
>   {
> -	char cval __attribute__((unused));
> -	short sval __attribute__((unused));
> -	int ival __attribute__((unused));
> -	long long lval __attribute__((unused));
> +	__u8 cvar __attribute__((unused));
> +	__u16 svar __attribute__((unused));
> +	__u32 ivar __attribute__((unused));
> +	__u64 lvar __attribute__((unused));
>   
>   	switch (len) {
>   	case 1:
> -		cval = *(char *)dummy_var;
> +		cvar = (__u8)glvar;
>   		break;
>   	case 2:
> -		sval = *(short *)dummy_var;
> +		svar = (__u16)glvar;
>   		break;
>   	case 4:
> -		ival = *(int *)dummy_var;
> +		ivar = (__u32)glvar;
>   		break;
>   	case 8:
> -		lval = *(long long *)dummy_var;
> +		lvar = (__u64)glvar;
>   		break;
>   	}
>   }
>   
> -/*
> - * Do the r/w accesses to trigger the breakpoints. And run
> - * the usual traps.
> - */
> -static void trigger_tests(void)
> +static void test_workload(void)
>   {
> -	int len, ret;
> +	__u8 cvar __attribute__((unused));
> +	int len = 0;
>   
> -	ret = ptrace(PTRACE_TRACEME, 0, NULL, 0);
> -	if (ret) {
> -		perror("Can't be traced?\n");
> -		return;
> +	if (ptrace(PTRACE_TRACEME, 0, NULL, 0)) {
> +		perror("Child can't be traced?");
> +		exit(-1);
>   	}
>   
>   	/* Wake up father so that it sets up the first test */
>   	kill(getpid(), SIGUSR1);
>   
> -	/* Test write watchpoints */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> +	/* PTRACE_SET_DEBUGREG. WO test */
> +	for (len = 1; len <= sizeof(glvar); len <<= 1)
>   		write_var(len);
>   
> -	/* Test read/write watchpoints (on read accesses) */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> +	/* PTRACE_SET_DEBUGREG. RO test */
> +	for (len = 1; len <= sizeof(glvar); len <<= 1)
>   		read_var(len);
>   
> -	/* Test when breakpoint is unset */
> +	/* PTRACE_SET_DEBUGREG. RW test */
> +	for (len = 1; len <= sizeof(glvar); len <<= 1) {
> +		if (rand() % 2)
> +			read_var(len);
> +		else
> +			write_var(len);
> +	}
>   
> -	/* Test write watchpoints */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> -		write_var(len);
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. WO test */
> +	write_var(1);
>   
> -	/* Test read/write watchpoints (on read accesses) */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> -		read_var(len);
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. RO test */
> +	read_var(1);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. RW test */
> +	if (rand() % 2)
> +		write_var(1);
> +	else
> +		read_var(1);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. WO test */
> +	gstruct.a[rand() % A_LEN] = 'a';
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. RO test */
> +	cvar = gstruct.a[rand() % A_LEN];
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. RW test */
> +	if (rand() % 2)
> +		gstruct.a[rand() % A_LEN] = 'a';
> +	else
> +		cvar = gstruct.a[rand() % A_LEN];
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. WO test */
> +	gstruct.b[rand() % B_LEN] = 'b';
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. RO test */
> +	cvar = gstruct.b[rand() % B_LEN];
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. RW test */
> +	if (rand() % 2)
> +		gstruct.b[rand() % B_LEN] = 'b';
> +	else
> +		cvar = gstruct.b[rand() % B_LEN];
> +
> +	/* PPC_PTRACE_SETHWDEBUG. DAWR_MAX_LEN. RW test */
> +	if (rand() % 2)
> +		big_var[rand() % DAWR_MAX_LEN] = 'a';
> +	else
> +		cvar = big_var[rand() % DAWR_MAX_LEN];
>   }
>   
> -static void check_success(const char *msg)
> +static void
> +check_success(pid_t child_pid, const char *name, const char *type, int len)
>   {
> -	const char *msg2;
>   	int status;
>   
>   	/* Wait for the child to SIGTRAP */
>   	wait(&status);
> +	if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGTRAP) {
> +		printf("%s, %s, len: %d: Fail\n", name, type, len);
> +		exit(-1);
> +	}
> +	printf("%s, %s, len: %d: Ok\n", name, type, len);
>   
> -	msg2 = "Failed";
> +	/*
> +	 * For ptrace registered watchpoint, signal is generated
> +	 * before executing load/store. Singlestep the instruction
> +	 * and then continue the test.
> +	 */
> +	ptrace(PTRACE_SINGLESTEP, child_pid, NULL, 0);
> +	wait(NULL);
> +}
>   
> -	if (WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP) {
> -		msg2 = "Child process hit the breakpoint";
> +static void ptrace_set_debugreg(pid_t child_pid, unsigned long wp_addr)
> +{
> +	if (ptrace(PTRACE_SET_DEBUGREG, child_pid, 0, wp_addr)) {
> +		perror("PTRACE_SET_DEBUGREG failed");
> +		exit(-1);
>   	}
> +}
> +
> +static int ptrace_sethwdebug(pid_t child_pid, struct ppc_hw_breakpoint *info)
> +{
> +	int wh = ptrace(PPC_PTRACE_SETHWDEBUG, child_pid, 0, info);
>   
> -	printf("%s Result: [%s]\n", msg, msg2);
> +	if (wh <= 0) {
> +		perror("PPC_PTRACE_SETHWDEBUG failed");
> +		exit(-1);
> +	}
> +	return wh;
>   }
>   
> -static void launch_watchpoints(char *buf, int mode, int len,
> -			       struct ppc_debug_info *dbginfo, bool dawr)
> +static void ptrace_delhwdebug(pid_t child_pid, int wh)
>   {
> -	const char *mode_str;
> -	unsigned long data = (unsigned long)(dummy_var);
> -	int wh, range;
> -
> -	data &= ~0x7UL;
> -
> -	if (mode == BP_W) {
> -		data |= (1UL << 1);
> -		mode_str = "write";
> -	} else {
> -		data |= (1UL << 0);
> -		data |= (1UL << 1);
> -		mode_str = "read";
> +	if (ptrace(PPC_PTRACE_DELHWDEBUG, child_pid, 0, wh) < 0) {
> +		perror("PPC_PTRACE_DELHWDEBUG failed");
> +		exit(-1);
>   	}
> +}
>   
> -	/* Set DABR_TRANSLATION bit */
> -	data |= (1UL << 2);
> +#define DABR_READ_SHIFT		0
> +#define DABR_WRITE_SHIFT	1
> +#define DABR_TRANSLATION_SHIFT	2
>   
> -	/* use PTRACE_SET_DEBUGREG breakpoints */
> -	set_breakpoint_addr((void *)data);
> -	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> -	sprintf(buf, "Test %s watchpoint with len: %d ", mode_str, len);
> -	check_success(buf);
> -	/* Unregister hw brkpoint */
> -	set_breakpoint_addr(NULL);
> +static int test_set_debugreg(pid_t child_pid)
> +{
> +	unsigned long wp_addr = (unsigned long)&glvar;
> +	char *name = "PTRACE_SET_DEBUGREG";
> +	int len;
> +
> +	/* PTRACE_SET_DEBUGREG. WO test*/
> +	wp_addr &= ~0x7UL;
> +	wp_addr |= (1UL << DABR_WRITE_SHIFT);
> +	wp_addr |= (1UL << DABR_TRANSLATION_SHIFT);
> +	for (len = 1; len <= sizeof(glvar); len <<= 1) {
> +		ptrace_set_debugreg(child_pid, wp_addr);
> +		ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +		check_success(child_pid, name, "WO", len);
> +	}
> +
> +	/* PTRACE_SET_DEBUGREG. RO test */
> +	wp_addr &= ~0x7UL;
> +	wp_addr |= (1UL << DABR_READ_SHIFT);
> +	wp_addr |= (1UL << DABR_TRANSLATION_SHIFT);
> +	for (len = 1; len <= sizeof(glvar); len <<= 1) {
> +		ptrace_set_debugreg(child_pid, wp_addr);
> +		ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +		check_success(child_pid, name, "RO", len);
> +	}
>   
> -	data = (data & ~7); /* remove dabr control bits */
> +	/* PTRACE_SET_DEBUGREG. RW test */
> +	wp_addr &= ~0x7UL;
> +	wp_addr |= (1Ul << DABR_READ_SHIFT);
> +	wp_addr |= (1UL << DABR_WRITE_SHIFT);
> +	wp_addr |= (1UL << DABR_TRANSLATION_SHIFT);
> +	for (len = 1; len <= sizeof(glvar); len <<= 1) {
> +		ptrace_set_debugreg(child_pid, wp_addr);
> +		ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +		check_success(child_pid, name, "RW", len);
> +	}
>   
> -	/* use PPC_PTRACE_SETHWDEBUG breakpoint */
> -	if (!(dbginfo->features & PPC_DEBUG_FEATURE_DATA_BP_RANGE))
> -		return; /* not supported */
> -	wh = set_hwbreakpoint_addr((void *)data, 0);
> -	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> -	sprintf(buf, "Test %s watchpoint with len: %d ", mode_str, len);
> -	check_success(buf);
> -	/* Unregister hw brkpoint */
> -	del_hwbreakpoint_addr(wh);
> -
> -	/* try a wider range */
> -	range = 8;
> -	if (dawr)
> -		range = 512 - ((int)data & (DAWR_LENGTH_MAX - 1));
> -	wh = set_hwbreakpoint_addr((void *)data, range);
> -	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> -	sprintf(buf, "Test %s watchpoint with len: %d ", mode_str, len);
> -	check_success(buf);
> -	/* Unregister hw brkpoint */
> -	del_hwbreakpoint_addr(wh);
> +	ptrace_set_debugreg(child_pid, 0);
> +	return 0;
>   }
>   
> -/* Set the breakpoints and check the child successfully trigger them */
> -static int launch_tests(bool dawr)
> +static void get_ppc_hw_breakpoint(struct ppc_hw_breakpoint *info, int type,
> +				  unsigned long addr, int len)
>   {
> -	char buf[1024];
> -	int len, i, status;
> +	info->version = 1;
> +	info->trigger_type = type;
> +	info->condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
> +	info->addr = (__u64)addr;
> +	info->addr2 = (__u64)addr + len;
> +	info->condition_value = 0;
> +	if (!len)
> +		info->addr_mode = PPC_BREAKPOINT_MODE_EXACT;
> +	else
> +		info->addr_mode = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
> +}
>   
> -	struct ppc_debug_info dbginfo;
> +static void test_sethwdebug_exact(pid_t child_pid)
> +{
> +	struct ppc_hw_breakpoint info;
> +	unsigned long wp_addr = (unsigned long)&glvar;
> +	char *name = "PPC_PTRACE_SETHWDEBUG, MODE_EXACT";
> +	int len = 1; /* hardcoded in kernel */
> +	int wh;
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. WO test */
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_WRITE, wp_addr, 0);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "WO", len);
> +	ptrace_delhwdebug(child_pid, wh);
>   
> -	i = ptrace(PPC_PTRACE_GETHWDBGINFO, child_pid, NULL, &dbginfo);
> -	if (i) {
> -		perror("Can't set breakpoint info\n");
> -		exit(-1);
> -	}
> -	if (!(dbginfo.features & PPC_DEBUG_FEATURE_DATA_BP_RANGE))
> -		printf("WARNING: Kernel doesn't support PPC_PTRACE_SETHWDEBUG\n");
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. RO test */
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_READ, wp_addr, 0);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RO", len);
> +	ptrace_delhwdebug(child_pid, wh);
>   
> -	/* Write watchpoint */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> -		launch_watchpoints(buf, BP_W, len, &dbginfo, dawr);
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_EXACT. RW test */
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_RW, wp_addr, 0);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RW", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +}
>   
> -	/* Read-Write watchpoint */
> -	for (len = 1; len <= sizeof(long); len <<= 1)
> -		launch_watchpoints(buf, BP_RW, len, &dbginfo, dawr);
> +static void test_sethwdebug_range_aligned(pid_t child_pid)
> +{
> +	struct ppc_hw_breakpoint info;
> +	unsigned long wp_addr;
> +	char *name = "PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED";
> +	int len;
> +	int wh;
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. WO test */
> +	wp_addr = (unsigned long)&gstruct.a;
> +	len = A_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_WRITE, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "WO", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. RO test */
> +	wp_addr = (unsigned long)&gstruct.a;
> +	len = A_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_READ, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RO", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW ALIGNED. RW test */
> +	wp_addr = (unsigned long)&gstruct.a;
> +	len = A_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_RW, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RW", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +}
>   
> +static void test_sethwdebug_range_unaligned(pid_t child_pid)
> +{
> +	struct ppc_hw_breakpoint info;
> +	unsigned long wp_addr;
> +	char *name = "PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW UNALIGNED";
> +	int len;
> +	int wh;
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. WO test */
> +	wp_addr = (unsigned long)&gstruct.b;
> +	len = B_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_WRITE, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "WO", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. RO test */
> +	wp_addr = (unsigned long)&gstruct.b;
> +	len = B_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_READ, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RO", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +
> +	/* PPC_PTRACE_SETHWDEBUG. MODE_RANGE. DW UNALIGNED. RW test */
> +	wp_addr = (unsigned long)&gstruct.b;
> +	len = B_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_RW, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
>   	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RW", len);
> +	ptrace_delhwdebug(child_pid, wh);
>   
> -	/*
> -	 * Now we have unregistered the breakpoint, access by child
> -	 * should not cause SIGTRAP.
> -	 */
> +}
>   
> -	wait(&status);
> +static void test_sethwdebug_dawr_max_range(pid_t child_pid)
> +{
> +	struct ppc_hw_breakpoint info;
> +	unsigned long wp_addr;
> +	char *name = "PPC_PTRACE_SETHWDEBUG, DAWR_MAX_LEN";
> +	int len;
> +	int wh;
> +
> +	/* PPC_PTRACE_SETHWDEBUG. DAWR_MAX_LEN. RW test */
> +	wp_addr = (unsigned long)big_var;
> +	len = DAWR_MAX_LEN;
> +	get_ppc_hw_breakpoint(&info, PPC_BREAKPOINT_TRIGGER_RW, wp_addr, len);
> +	wh = ptrace_sethwdebug(child_pid, &info);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "RW", len);
> +	ptrace_delhwdebug(child_pid, wh);
> +}
>   
> -	if (WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP) {
> -		printf("FAIL: Child process hit the breakpoint, which is not expected\n");
> -		ptrace(PTRACE_CONT, child_pid, NULL, 0);
> -		return TEST_FAIL;
> +/* Set the breakpoints and check the child successfully trigger them */
> +static void
> +run_tests(pid_t child_pid, struct ppc_debug_info *dbginfo, bool dawr)
> +{
> +	test_set_debugreg(child_pid);
> +	if (dbginfo->features & PPC_DEBUG_FEATURE_DATA_BP_RANGE) {
> +		test_sethwdebug_exact(child_pid);
> +		test_sethwdebug_range_aligned(child_pid);
> +		test_sethwdebug_range_unaligned(child_pid);
> +
> +		if (dawr)
> +			test_sethwdebug_dawr_max_range(child_pid);
>   	}
> -
> -	if (WIFEXITED(status))
> -		printf("Child exited normally\n");
> -
> -	return TEST_PASS;
>   }
>   
>   static int ptrace_hwbreak(void)
>   {
> -	pid_t pid;
> -	int ret;
> +	pid_t child_pid;
> +	struct ppc_debug_info dbginfo;
>   	bool dawr;
>   
> -	pid = fork();
> -	if (!pid) {
> -		trigger_tests();
> +	child_pid = fork();
> +	if (!child_pid) {
> +		test_workload();
>   		return 0;
>   	}
>   
>   	wait(NULL);
>   
> -	child_pid = pid;
> -
> -	get_dbginfo();
> -	SKIP_IF(!hwbreak_present());
> -	dawr = dawr_present();
> +	get_dbginfo(child_pid, &dbginfo);
> +	SKIP_IF(dbginfo.num_data_bps == 0);
>   
> -	ret = launch_tests(dawr);
> +	dawr = dawr_present(&dbginfo);
> +	run_tests(child_pid, &dbginfo, dawr);
>   
> +	/* Let the child exit first. */
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
>   	wait(NULL);
>   
> -	return ret;
> +	/*
> +	 * Testcases exits immediately with -1 on any failure. If
> +	 * it has reached here, it means all tests were successful.
> +	 */
> +	return TEST_PASS;
>   }
>   
>   int main(int argc, char **argv, char **envp)