Re: [PATCH v6 8/8] powerpc/watchpoint/selftests: Tests for kernel accessing user memory

From: Rogerio Alves <rcardoso@linux.ibm.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
	mpe@ellerman.id.au, christophe.leroy@c-s.fr
Cc: mikey@neuling.org, jniethe5@gmail.com, pedromfc@linux.ibm.com,
	linux-kernel@vger.kernel.org, paulus@samba.org,
	rogealve@linux.ibm.com, naveen.n.rao@linux.vnet.ibm.com,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v6 8/8] powerpc/watchpoint/selftests: Tests for kernel accessing user memory
Date: Thu, 17 Sep 2020 10:26:20 -0300	[thread overview]
Message-ID: <05c1b4a3-a0e7-6fcb-171b-1a2e8a99f21d@linux.ibm.com> (raw)
In-Reply-To: <20200902042945.129369-9-ravi.bangoria@linux.ibm.com>


On 9/2/20 1:29 AM, Ravi Bangoria wrote:
> Introduce tests to cover simple scenarios where user is watching
> memory which can be accessed by kernel as well. We also support
> _MODE_EXACT with _SETHWDEBUG interface. Move those testcases out-
> side of _BP_RANGE condition. This will help to test _MODE_EXACT
> scenarios when CONFIG_HAVE_HW_BREAKPOINT is not set, eg:
> 
>    $ ./ptrace-hwbreak
>    ...
>    PTRACE_SET_DEBUGREG, Kernel Access Userspace, 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_EXACT, Kernel Access Userspace, len: 1: Ok
>    success: ptrace-hwbreak
> 
> Suggested-by: Pedro Miraglia Franco de Carvalho <pedromfc@linux.ibm.com>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Tested-by: Rogerio Alves <rcardoso@linux.ibm.com>
> ---
>   .../selftests/powerpc/ptrace/ptrace-hwbreak.c | 48 ++++++++++++++++++-
>   1 file changed, 46 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> index fc477dfe86a2..2e0d86e0687e 100644
> --- a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> +++ b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
> @@ -20,6 +20,8 @@
>   #include <signal.h>
>   #include <sys/types.h>
>   #include <sys/wait.h>
> +#include <sys/syscall.h>
> +#include <linux/limits.h>
>   #include "ptrace.h"
>   
>   #define SPRN_PVR	0x11F
> @@ -44,6 +46,7 @@ struct gstruct {
>   };
>   static volatile struct gstruct gstruct __attribute__((aligned(512)));
>   
> +static volatile char cwd[PATH_MAX] __attribute__((aligned(8)));
>   
>   static void get_dbginfo(pid_t child_pid, struct ppc_debug_info *dbginfo)
>   {
> @@ -138,6 +141,9 @@ static void test_workload(void)
>   			write_var(len);
>   	}
>   
> +	/* PTRACE_SET_DEBUGREG, Kernel Access Userspace test */
> +	syscall(__NR_getcwd, &cwd, PATH_MAX);
> +
>   	/* PPC_PTRACE_SETHWDEBUG, MODE_EXACT, WO test */
>   	write_var(1);
>   
> @@ -150,6 +156,9 @@ static void test_workload(void)
>   	else
>   		read_var(1);
>   
> +	/* PPC_PTRACE_SETHWDEBUG, MODE_EXACT, Kernel Access Userspace test */
> +	syscall(__NR_getcwd, &cwd, PATH_MAX);
> +
>   	/* PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, WO test */
>   	gstruct.a[rand() % A_LEN] = 'a';
>   
> @@ -293,6 +302,24 @@ static int test_set_debugreg(pid_t child_pid)
>   	return 0;
>   }
>   
> +static int test_set_debugreg_kernel_userspace(pid_t child_pid)
> +{
> +	unsigned long wp_addr = (unsigned long)cwd;
> +	char *name = "PTRACE_SET_DEBUGREG";
> +
> +	/* PTRACE_SET_DEBUGREG, Kernel Access Userspace test */
> +	wp_addr &= ~0x7UL;
> +	wp_addr |= (1Ul << DABR_READ_SHIFT);
> +	wp_addr |= (1UL << DABR_WRITE_SHIFT);
> +	wp_addr |= (1UL << DABR_TRANSLATION_SHIFT);
> +	ptrace_set_debugreg(child_pid, wp_addr);
> +	ptrace(PTRACE_CONT, child_pid, NULL, 0);
> +	check_success(child_pid, name, "Kernel Access Userspace", wp_addr, 8);
> +
> +	ptrace_set_debugreg(child_pid, 0);
> +	return 0;
> +}
> +
>   static void get_ppc_hw_breakpoint(struct ppc_hw_breakpoint *info, int type,
>   				  unsigned long addr, int len)
>   {
> @@ -338,6 +365,22 @@ static void test_sethwdebug_exact(pid_t child_pid)
>   	ptrace_delhwdebug(child_pid, wh);
>   }
>   
> +static void test_sethwdebug_exact_kernel_userspace(pid_t child_pid)
> +{
> +	struct ppc_hw_breakpoint info;
> +	unsigned long wp_addr = (unsigned long)&cwd;
> +	char *name = "PPC_PTRACE_SETHWDEBUG, MODE_EXACT";
> +	int len = 1; /* hardcoded in kernel */
> +	int wh;
> +
> +	/* PPC_PTRACE_SETHWDEBUG, MODE_EXACT, Kernel Access Userspace 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, "Kernel Access Userspace", wp_addr, len);
> +	ptrace_delhwdebug(child_pid, wh);
> +}
> +
>   static void test_sethwdebug_range_aligned(pid_t child_pid)
>   {
>   	struct ppc_hw_breakpoint info;
> @@ -452,9 +495,10 @@ static void
>   run_tests(pid_t child_pid, struct ppc_debug_info *dbginfo, bool dawr)
>   {
>   	test_set_debugreg(child_pid);
> +	test_set_debugreg_kernel_userspace(child_pid);
> +	test_sethwdebug_exact(child_pid);
> +	test_sethwdebug_exact_kernel_userspace(child_pid);
>   	if (dbginfo->features & PPC_DEBUG_FEATURE_DATA_BP_RANGE) {
> -		test_sethwdebug_exact(child_pid);
> -
>   		test_sethwdebug_range_aligned(child_pid);
>   		if (dawr || is_8xx) {
>   			test_sethwdebug_range_unaligned(child_pid);
>