* [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls
@ 2021-05-20 11:19 Nicholas Piggin
2021-05-20 11:19 ` [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with " Nicholas Piggin
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Nicholas Piggin @ 2021-05-20 11:19 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Nicholas Piggin, Dmitry V. Levin
The sc and scv 0 system calls have different ABI conventions, and
ptracers need to know which system call type is being used if it wants
to look at the syscall registers.
Document that pt_regs.trap can be used for this, and fix one in-tree user
to work with scv 0 syscalls.
Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
Suggested-by: "Dmitry V. Levin" <ldv@altlinux.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
Documentation/powerpc/syscall64-abi.rst | 10 +++++++
tools/testing/selftests/seccomp/seccomp_bpf.c | 27 ++++++++++++-------
2 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/Documentation/powerpc/syscall64-abi.rst b/Documentation/powerpc/syscall64-abi.rst
index dabee3729e5a..56490c4c0c07 100644
--- a/Documentation/powerpc/syscall64-abi.rst
+++ b/Documentation/powerpc/syscall64-abi.rst
@@ -109,6 +109,16 @@ auxiliary vector.
scv 0 syscalls will always behave as PPC_FEATURE2_HTM_NOSC.
+ptrace
+------
+When ptracing system calls (PTRACE_SYSCALL), the pt_regs.trap value contains
+the system call type that can be used to distinguish between sc and scv 0
+system calls, and the different register conventions can be accounted for.
+
+If the value of (pt_regs.trap & 0xfff0) is 0xc00 then the system call was
+performed with the sc instruction, if it is 0x3000 then the system call was
+performed with the scv 0 instruction.
+
vsyscall
========
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 98c3b647f54d..e3d5c77a8612 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -1753,16 +1753,25 @@ TEST_F(TRACE_poke, getpid_runs_normally)
# define SYSCALL_RET_SET(_regs, _val) \
do { \
typeof(_val) _result = (_val); \
- /* \
- * A syscall error is signaled by CR0 SO bit \
- * and the code is stored as a positive value. \
- */ \
- if (_result < 0) { \
- SYSCALL_RET(_regs) = -_result; \
- (_regs).ccr |= 0x10000000; \
- } else { \
+ if ((_regs.trap & 0xfff0) == 0x3000) { \
+ /* \
+ * scv 0 system call uses -ve result \
+ * for error, so no need to adjust. \
+ */ \
SYSCALL_RET(_regs) = _result; \
- (_regs).ccr &= ~0x10000000; \
+ } else { \
+ /* \
+ * A syscall error is signaled by the \
+ * CR0 SO bit and the code is stored as \
+ * a positive value. \
+ */ \
+ if (_result < 0) { \
+ SYSCALL_RET(_regs) = -_result; \
+ (_regs).ccr |= 0x10000000; \
+ } else { \
+ SYSCALL_RET(_regs) = _result; \
+ (_regs).ccr &= ~0x10000000; \
+ } \
} \
} while (0)
# define SYSCALL_RET_SET_ON_PTRACE_EXIT
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with scv syscalls
2021-05-20 11:19 [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls Nicholas Piggin
@ 2021-05-20 11:19 ` Nicholas Piggin
2021-05-20 11:45 ` Dmitry V. Levin
2021-05-20 11:41 ` [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and " Dmitry V. Levin
2021-05-21 12:44 ` Michael Ellerman
2 siblings, 1 reply; 5+ messages in thread
From: Nicholas Piggin @ 2021-05-20 11:19 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Nicholas Piggin, Dmitry V. Levin
The scv implementation missed updating syscall return value and error
value get/set functions to deal with the changed register ABI. This
broke ptrace PTRACE_GET_SYSCALL_INFO as well as some kernel auditing
and tracing functions.
Fix. tools/testing/selftests/ptrace/get_syscall_info now passes when
scv is used.
Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/include/asm/ptrace.h | 45 +++++++++++++++++-------------
arch/powerpc/include/asm/syscall.h | 42 +++++++++++++++++-----------
2 files changed, 52 insertions(+), 35 deletions(-)
diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 9c9ab2746168..b476a685f066 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -19,6 +19,7 @@
#ifndef _ASM_POWERPC_PTRACE_H
#define _ASM_POWERPC_PTRACE_H
+#include <linux/err.h>
#include <uapi/asm/ptrace.h>
#include <asm/asm-const.h>
@@ -152,25 +153,6 @@ extern unsigned long profile_pc(struct pt_regs *regs);
long do_syscall_trace_enter(struct pt_regs *regs);
void do_syscall_trace_leave(struct pt_regs *regs);
-#define kernel_stack_pointer(regs) ((regs)->gpr[1])
-static inline int is_syscall_success(struct pt_regs *regs)
-{
- return !(regs->ccr & 0x10000000);
-}
-
-static inline long regs_return_value(struct pt_regs *regs)
-{
- if (is_syscall_success(regs))
- return regs->gpr[3];
- else
- return -regs->gpr[3];
-}
-
-static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
-{
- regs->gpr[3] = rc;
-}
-
#ifdef __powerpc64__
#define user_mode(regs) ((((regs)->msr) >> MSR_PR_LG) & 0x1)
#else
@@ -235,6 +217,31 @@ static __always_inline void set_trap_norestart(struct pt_regs *regs)
regs->trap |= 0x1;
}
+#define kernel_stack_pointer(regs) ((regs)->gpr[1])
+static inline int is_syscall_success(struct pt_regs *regs)
+{
+ if (trap_is_scv(regs))
+ return !IS_ERR_VALUE((unsigned long)regs->gpr[3]);
+ else
+ return !(regs->ccr & 0x10000000);
+}
+
+static inline long regs_return_value(struct pt_regs *regs)
+{
+ if (trap_is_scv(regs))
+ return regs->gpr[3];
+
+ if (is_syscall_success(regs))
+ return regs->gpr[3];
+ else
+ return -regs->gpr[3];
+}
+
+static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
+{
+ regs->gpr[3] = rc;
+}
+
#define arch_has_single_step() (1)
#define arch_has_block_step() (true)
#define ARCH_HAS_USER_SINGLE_STEP_REPORT
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index fd1b518eed17..ba0f88f3a30d 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -41,11 +41,17 @@ static inline void syscall_rollback(struct task_struct *task,
static inline long syscall_get_error(struct task_struct *task,
struct pt_regs *regs)
{
- /*
- * If the system call failed,
- * regs->gpr[3] contains a positive ERRORCODE.
- */
- return (regs->ccr & 0x10000000UL) ? -regs->gpr[3] : 0;
+ if (trap_is_scv(regs)) {
+ unsigned long error = regs->gpr[3];
+
+ return IS_ERR_VALUE(error) ? error : 0;
+ } else {
+ /*
+ * If the system call failed,
+ * regs->gpr[3] contains a positive ERRORCODE.
+ */
+ return (regs->ccr & 0x10000000UL) ? -regs->gpr[3] : 0;
+ }
}
static inline long syscall_get_return_value(struct task_struct *task,
@@ -58,18 +64,22 @@ static inline void syscall_set_return_value(struct task_struct *task,
struct pt_regs *regs,
int error, long val)
{
- /*
- * In the general case it's not obvious that we must deal with CCR
- * here, as the syscall exit path will also do that for us. However
- * there are some places, eg. the signal code, which check ccr to
- * decide if the value in r3 is actually an error.
- */
- if (error) {
- regs->ccr |= 0x10000000L;
- regs->gpr[3] = error;
+ if (trap_is_scv(regs)) {
+ regs->gpr[3] = (long) error ?: val;
} else {
- regs->ccr &= ~0x10000000L;
- regs->gpr[3] = val;
+ /*
+ * In the general case it's not obvious that we must deal with
+ * CCR here, as the syscall exit path will also do that for us.
+ * However there are some places, eg. the signal code, which
+ * check ccr to decide if the value in r3 is actually an error.
+ */
+ if (error) {
+ regs->ccr |= 0x10000000L;
+ regs->gpr[3] = error;
+ } else {
+ regs->ccr &= ~0x10000000L;
+ regs->gpr[3] = val;
+ }
}
}
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls
2021-05-20 11:19 [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls Nicholas Piggin
2021-05-20 11:19 ` [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with " Nicholas Piggin
@ 2021-05-20 11:41 ` Dmitry V. Levin
2021-05-21 12:44 ` Michael Ellerman
2 siblings, 0 replies; 5+ messages in thread
From: Dmitry V. Levin @ 2021-05-20 11:41 UTC (permalink / raw)
To: Nicholas Piggin; +Cc: linuxppc-dev
On Thu, May 20, 2021 at 09:19:30PM +1000, Nicholas Piggin wrote:
> The sc and scv 0 system calls have different ABI conventions, and
> ptracers need to know which system call type is being used if it wants
> to look at the syscall registers.
typo: s/if it wants/if they want/
> Document that pt_regs.trap can be used for this, and fix one in-tree user
> to work with scv 0 syscalls.
>
> Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
> Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
> Suggested-by: "Dmitry V. Levin" <ldv@altlinux.org>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Also consider adding
Cc: stable@vger.kernel.org # 5.9+
Besides that, looks good, thanks!
--
ldv
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with scv syscalls
2021-05-20 11:19 ` [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with " Nicholas Piggin
@ 2021-05-20 11:45 ` Dmitry V. Levin
0 siblings, 0 replies; 5+ messages in thread
From: Dmitry V. Levin @ 2021-05-20 11:45 UTC (permalink / raw)
To: Nicholas Piggin; +Cc: linuxppc-dev
On Thu, May 20, 2021 at 09:19:31PM +1000, Nicholas Piggin wrote:
> The scv implementation missed updating syscall return value and error
> value get/set functions to deal with the changed register ABI. This
> broke ptrace PTRACE_GET_SYSCALL_INFO as well as some kernel auditing
> and tracing functions.
>
> Fix. tools/testing/selftests/ptrace/get_syscall_info now passes when
> scv is used.
>
> Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
> Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Thanks, feel free to add
Reviewed-by: Dmitry V. Levin <ldv@altlinux.org>
Also consider adding
Cc: stable@vger.kernel.org # 5.9+
--
ldv
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls
2021-05-20 11:19 [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls Nicholas Piggin
2021-05-20 11:19 ` [PATCH 2/2] powerpc/64s/syscall: Fix ptrace syscall info with " Nicholas Piggin
2021-05-20 11:41 ` [PATCH 1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and " Dmitry V. Levin
@ 2021-05-21 12:44 ` Michael Ellerman
2 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2021-05-21 12:44 UTC (permalink / raw)
To: linuxppc-dev, Nicholas Piggin; +Cc: Dmitry V. Levin
On Thu, 20 May 2021 21:19:30 +1000, Nicholas Piggin wrote:
> The sc and scv 0 system calls have different ABI conventions, and
> ptracers need to know which system call type is being used if it wants
> to look at the syscall registers.
>
> Document that pt_regs.trap can be used for this, and fix one in-tree user
> to work with scv 0 syscalls.
Applied to powerpc/fixes.
[1/2] powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls
https://git.kernel.org/powerpc/c/5665bc35c1ed917ac8fd06cb651317bb47a65b10
[2/2] powerpc/64s/syscall: Fix ptrace syscall info with scv syscalls
https://git.kernel.org/powerpc/c/d72500f992849d31ebae8f821a023660ddd0dcc2
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
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