* [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER
@ 2026-02-20 10:50 Magnus Lindholm
2026-02-20 10:50 ` [PATCH v2 1/1] " Magnus Lindholm
2026-02-24 8:53 ` [PATCH v2 0/1] " Michael Cree
0 siblings, 2 replies; 3+ messages in thread
From: Magnus Lindholm @ 2026-02-20 10:50 UTC (permalink / raw)
To: richard.henderson, mattst88, linux-kernel, linux-alpha, corbet,
linux-doc
Cc: glaubitz, macro, macro, mcree, ink, Magnus Lindholm
This patch adds SECCOMP and SECCOMP_FILTER support to the Alpha
architecture.
The seccomp-bpf selftests exercise syscall tracing, restart, and signal
interaction paths that were previously untested on Alpha. To support
these, the ptrace/strace syscall path is updated to reliably distinguish
internal skip-dispatch from userspace invalid syscall numbers, ensuring
that syscall(-1) continues to return -ENOSYS with correct r0/a3
semantics.
Supporting seccomp also requires correct syscall restart handling when
ptrace and signal delivery are involved. The traced syscall entry path
now consistently tracks syscall state using r0, r1, and r2 while
preserving Alpha's a3-based error reporting ABI:
- r1 holds the mutable "current" syscall number
- r2 preserves the original syscall number for restart
- r0 and r19 (a3) retain their traditional roles as return value and
error indicator
This separation allows syscall restarts to be gated strictly on valid
ERESTART* return codes in the ptrace/strace paths and prevents
kernel-internal restart values from leaking into userspace.
Alpha also lacked support for PTRACE_GETREGSET(NT_PRSTATUS), causing
ptrace-based seccomp tests to fail with -EIO. Minimal GETREGSET and
SETREGSET support is added to export struct pt_regs directly.
With these changes applied, the seccomp-bpf and ptrace syscall selftests
(seccomp_bpf, extended for Alpha) pass reliably on Alpha systems.
---
Changes since v1:
- Update features documentation for seccomp-filter/alpha
Link: https://lore.kernel.org/linux-alpha/20260205133049.526-1-linmag7@gmail.com/T/#t
Magnus Lindholm (1):
alpha: add support for SECCOMP and SECCOMP_FILTER
.../seccomp/seccomp-filter/arch-support.txt | 2 +-
arch/alpha/Kconfig | 2 +
arch/alpha/include/asm/seccomp.h | 13 ++
arch/alpha/include/asm/syscall.h | 90 ++++++++++++-
arch/alpha/include/asm/thread_info.h | 16 ++-
arch/alpha/kernel/entry.S | 123 +++++++++++++++---
arch/alpha/kernel/ptrace.c | 83 +++++++++++-
7 files changed, 305 insertions(+), 24 deletions(-)
create mode 100644 arch/alpha/include/asm/seccomp.h
--
2.52.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH v2 1/1] alpha: add support for SECCOMP and SECCOMP_FILTER
2026-02-20 10:50 [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER Magnus Lindholm
@ 2026-02-20 10:50 ` Magnus Lindholm
2026-02-24 8:53 ` [PATCH v2 0/1] " Michael Cree
1 sibling, 0 replies; 3+ messages in thread
From: Magnus Lindholm @ 2026-02-20 10:50 UTC (permalink / raw)
To: richard.henderson, mattst88, linux-kernel, linux-alpha, corbet,
linux-doc
Cc: glaubitz, macro, macro, mcree, ink, Magnus Lindholm
Add SECCOMP and SECCOMP_FILTER support to the Alpha architecture and fix
syscall entry and ptrace issues uncovered by the seccomp-bpf selftests.
The syscall entry path is reworked to consistently track syscall state
using r0, r1 and r2:
- r1 holds the active syscall number
- r2 preserves the original syscall number for restart
- r0 carries the return value, with r19 (a3) indicating success/error
This allows syscall restarts to be permitted only for valid ERESTART*
return codes and prevents kernel-internal restart values from leaking to
userspace. The syscall tracing error marker is corrected to use the saved
syscall number slot, matching the Alpha ABI.
Additionally, implement minimal PTRACE_GETREGSET and PTRACE_SETREGSET
support for NT_PRSTATUS, exporting struct pt_regs directly. This fixes
ptrace-based seccomp tests that previously failed with -EIO.
With these changes, seccomp-bpf and ptrace syscall tests pass reliably on
Alpha.
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
---
.../seccomp/seccomp-filter/arch-support.txt | 2 +-
arch/alpha/Kconfig | 2 +
arch/alpha/include/asm/seccomp.h | 13 ++
arch/alpha/include/asm/syscall.h | 90 ++++++++++++-
arch/alpha/include/asm/thread_info.h | 16 ++-
arch/alpha/kernel/entry.S | 123 +++++++++++++++---
arch/alpha/kernel/ptrace.c | 83 +++++++++++-
7 files changed, 305 insertions(+), 24 deletions(-)
create mode 100644 arch/alpha/include/asm/seccomp.h
diff --git a/Documentation/features/seccomp/seccomp-filter/arch-support.txt b/Documentation/features/seccomp/seccomp-filter/arch-support.txt
index 13feb679649e..9336bdfc125c 100644
--- a/Documentation/features/seccomp/seccomp-filter/arch-support.txt
+++ b/Documentation/features/seccomp/seccomp-filter/arch-support.txt
@@ -6,7 +6,7 @@
-----------------------
| arch |status|
-----------------------
- | alpha: | TODO |
+ | alpha: | ok |
| arc: | TODO |
| arm: | ok |
| arm64: | ok |
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 6c7dbf0adad6..7b7dafe7d9df 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -31,6 +31,8 @@ config ALPHA
select GENERIC_SMP_IDLE_THREAD
select HAS_IOPORT
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_SECCOMP
+ select HAVE_ARCH_SECCOMP_FILTER
select HAVE_MOD_ARCH_SPECIFIC
select LOCK_MM_AND_FIND_VMA
select MODULES_USE_ELF_RELA
diff --git a/arch/alpha/include/asm/seccomp.h b/arch/alpha/include/asm/seccomp.h
new file mode 100644
index 000000000000..311934d20340
--- /dev/null
+++ b/arch/alpha/include/asm/seccomp.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ALPHA_SECCOMP_H
+#define _ASM_ALPHA_SECCOMP_H
+
+#include <asm/unistd.h>
+#include <asm-generic/seccomp.h>
+#include <uapi/linux/audit.h>
+
+#define SECCOMP_ARCH_NATIVE AUDIT_ARCH_ALPHA
+#define SECCOMP_ARCH_NATIVE_NR NR_syscalls
+#define SECCOMP_ARCH_NATIVE_NAME "alpha"
+
+#endif /* _ASM_ALPHA_SECCOMP_H */
diff --git a/arch/alpha/include/asm/syscall.h b/arch/alpha/include/asm/syscall.h
index f21babaeed85..584b1ab2e325 100644
--- a/arch/alpha/include/asm/syscall.h
+++ b/arch/alpha/include/asm/syscall.h
@@ -3,6 +3,10 @@
#define _ASM_ALPHA_SYSCALL_H
#include <uapi/linux/audit.h>
+#include <linux/audit.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <asm/ptrace.h>
static inline int syscall_get_arch(struct task_struct *task)
{
@@ -12,7 +16,91 @@ static inline int syscall_get_arch(struct task_struct *task)
static inline long syscall_get_return_value(struct task_struct *task,
struct pt_regs *regs)
{
- return regs->r0;
+ return regs->r19 ? -(long)regs->r0 : (long)regs->r0;
+}
+
+/*
+ * Alpha syscall ABI / kernel conventions:
+ * - PAL provides syscall number in r0 on entry.
+ * - The kernel tracks the active syscall number in regs->r1 (mutable) and
+ * preserves the original syscall number in regs->r2 for rollback/restart.
+ * - Return value is in regs->r0, with regs->r19 ("a3") as the error flag
+ * (0=success, 1=error; on error regs->r0 holds positive errno).
+ */
+
+static inline long syscall_get_nr(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return (long)regs->r1;
+}
+
+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ long nr)
+{
+ regs->r1 = (unsigned long)nr;
+}
+
+/*
+ * Syscall arguments:
+ * regs->r16..regs->r21 carry up to 6 syscall arguments on entry.
+ * Note: regs->r19 is also used as "a3" (error flag) on syscall return.
+ */
+
+static inline void syscall_get_arguments(struct task_struct *task,
+ struct pt_regs *regs,
+ unsigned long *args)
+{
+ args[0] = regs->r16;
+ args[1] = regs->r17;
+ args[2] = regs->r18;
+ args[3] = regs->r19;
+ args[4] = regs->r20;
+ args[5] = regs->r21;
+}
+
+static inline void syscall_set_arguments(struct task_struct *task,
+ struct pt_regs *regs,
+ const unsigned long *args)
+{
+ regs->r16 = args[0];
+ regs->r17 = args[1];
+ regs->r18 = args[2];
+ regs->r19 = args[3];
+ regs->r20 = args[4];
+ regs->r21 = args[5];
+}
+/*
+ * Set return value for a syscall.
+ * Alpha uses r0 for return value and r19 ("a3") as the error indicator:
+ * a3 = 0 => success
+ * a3 = 1 => error, and userspace interprets r0 as errno (positive).
+ *
+ * The kernel reports errors to userspace by setting a3=1 and placing a
+ * positive errno value in r0. Some syscall paths do this in entry.S,
+ * while others (e.g. seccomp/ptrace helpers) use syscall_set_return_value().
+ */
+
+static inline void syscall_set_return_value(struct task_struct *task,
+ struct pt_regs *regs,
+ int error, long val)
+{
+
+ if (error) {
+ /* error is negative errno in this tree */
+ regs->r0 = (unsigned long)(-error); /* positive errno */
+ regs->r19 = 1; /* a3 = error */
+ } else {
+ regs->r0 = (unsigned long)val;
+ regs->r19 = 0; /* a3 = success */
+ }
+}
+
+/* Restore the original syscall nr after seccomp/ptrace modified regs->r1. */
+static inline void syscall_rollback(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ regs->r1 = regs->r2;
}
#endif /* _ASM_ALPHA_SYSCALL_H */
diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h
index 98ccbca64984..94ef9cfa30f5 100644
--- a/arch/alpha/include/asm/thread_info.h
+++ b/arch/alpha/include/asm/thread_info.h
@@ -56,7 +56,8 @@ register unsigned long *current_stack_pointer __asm__ ("$30");
* - pending work-to-be-done flags come first and must be assigned to be
* within bits 0 to 7 to fit in and immediate operand.
*
- * TIF_SYSCALL_TRACE is known to be 0 via blbs.
+ * (Historically TIF_SYSCALL_TRACE was known to be 0 via blbs, but we may
+ * also test multiple bits via masks now.)
*/
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
@@ -64,6 +65,7 @@ register unsigned long *current_stack_pointer __asm__ ("$30");
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_SYSCALL_AUDIT 4 /* syscall audit active */
#define TIF_NOTIFY_SIGNAL 5 /* signal notifications exist */
+#define TIF_SECCOMP 6 /* seccomp syscall filtering active */
#define TIF_DIE_IF_KERNEL 9 /* dik recursion lock */
#define TIF_MEMDIE 13 /* is terminating due to OOM killer */
#define TIF_POLLING_NRFLAG 14 /* idle is polling for TIF_NEED_RESCHED */
@@ -74,8 +76,20 @@ register unsigned long *current_stack_pointer __asm__ ("$30");
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_NOTIFY_SIGNAL (1<<TIF_NOTIFY_SIGNAL)
+#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+/*
+ * Work to do on syscall entry (in entry.S).
+ * If you want this to exactly mirror what entry.S checks, keep it aligned
+ * with the mask used before branching to syscall_trace_enter().
+ */
+#ifdef CONFIG_AUDITSYSCALL
+# define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP)
+#else
+# define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SECCOMP)
+#endif
+
/* Work to do on interrupt/exception return. */
#define _TIF_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL)
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index f4d41b4538c2..6e09115ad406 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -10,6 +10,7 @@
#include <asm/pal.h>
#include <asm/errno.h>
#include <asm/unistd.h>
+#include <linux/errno.h>
.text
.set noat
@@ -35,6 +36,64 @@
.size \func, . - \func
.endm
+/*
+ * SYSCALL_SKIP_RETURN_RESTART_GATE
+ *
+ * Used when syscall dispatch is skipped (seccomp/ptrace injected nr=-1).
+ * - Ensure we never return r0==-1 with a3==0 (success); convert to ENOSYS.
+ * - Gate whether syscall restart is allowed by preserving restart context
+ * only for ERESTART* returns. Result:
+ * $26 = 0 => restart allowed
+ * $26 = 1 => restart NOT allowed
+ * $18 = preserved syscall nr (regs->r2) if restart allowed, else 0
+ */
+.macro SYSCALL_SKIP_RETURN_RESTART_GATE
+ /* Fix up invalid "-1 success" return state. */
+ ldq $19, 72($sp) /* a3 */
+ bne $19, 1f /* already error => skip fixup */
+
+ ldq $20, 0($sp) /* r0 */
+ lda $21, -1($31)
+ cmpeq $20, $21, $22
+ beq $22, 1f /* r0 != -1 => skip fixup */
+
+
+ lda $20, ENOSYS($31)
+ stq $20, 0($sp) /* r0 = ENOSYS */
+ lda $19, 1($31)
+ stq $19, 72($sp) /* a3 = 1 */
+1:
+ /* Restart gating: success is never restartable here. */
+ ldq $19, 72($sp) /* a3 */
+ beq $19, 3f /* success => not restartable */
+
+ ldq $20, 0($sp) /* r0 (positive errno if a3==1) */
+ lda $21, ERESTARTSYS($31)
+ cmpeq $20, $21, $22
+ bne $22, 2f
+ lda $21, ERESTARTNOINTR($31)
+ cmpeq $20, $21, $22
+ bne $22, 2f
+ lda $21, ERESTARTNOHAND($31)
+ cmpeq $20, $21, $22
+ bne $22, 2f
+ lda $21, ERESTART_RESTARTBLOCK($31)
+ cmpeq $20, $21, $22
+ bne $22, 2f
+
+3: /* Not a restart code (or success) => restart NOT allowed. */
+ addq $31, 1, $26 /* $26=1 => restart NOT allowed */
+ mov 0, $18
+ br 4f
+
+2: /* Restart allowed. */
+ ldq $18, 16($sp) /* preserved syscall nr (regs->r2) */
+ mov $31, $26 /* $26=0 => restart allowed */
+ br 4f
+4:
+.endm
+
+
/*
* This defines the normal kernel pt-regs layout.
*
@@ -425,7 +484,7 @@ CFI_START_OSF_FRAME entDbg
mov $sp, $16
jsr $31, do_entDbg
CFI_END_OSF_FRAME entDbg
-\f
+
/*
* The system call entry point is special. Most importantly, it looks
* like a function call to userspace as far as clobbered registers. We
@@ -435,6 +494,17 @@ CFI_END_OSF_FRAME entDbg
* So much for theory. We don't take advantage of this yet.
*
* Note that a0-a2 are not saved by PALcode as with the other entry points.
+ *
+ * Alpha syscall ABI uses:
+ * - r0 for return value
+ * - r19 ("a3") as error indicator (0=success, 1=error; r0 holds errno)
+ *
+ * For seccomp/ptrace/generic syscall helpers we track the syscall
+ * number separately:
+ * - regs->r1: current (mutable) syscall number (may be changed or set to -1)
+ * - regs->r2: original syscall number for restart/rollback
+ *
+ * On entry PAL provides the syscall number in r0; copy it into r1/r2.
*/
.align 4
@@ -447,6 +517,10 @@ CFI_END_OSF_FRAME entDbg
.cfi_rel_offset $gp, 16
entSys:
SAVE_ALL
+ ldq $1, 0($sp) /* syscall nr from saved r0 */
+ stq $1, 8($sp) /* regs->r1 = shadow syscall nr */
+ stq $1, 16($sp) /* regs->r2 = restart syscall nr */
+
lda $8, 0x3fff
bic $sp, $8, $8
lda $4, NR_syscalls($31)
@@ -462,15 +536,19 @@ entSys:
.cfi_rel_offset $17, SP_OFF+32
.cfi_rel_offset $18, SP_OFF+40
#ifdef CONFIG_AUDITSYSCALL
- lda $6, _TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT
+ lda $6, _TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP
and $3, $6, $3
bne $3, strace
#else
- blbs $3, strace /* check for SYSCALL_TRACE in disguise */
+ lda $6, _TIF_SYSCALL_TRACE | _TIF_SECCOMP
+ and $3, $6, $3
+ bne $3, strace
#endif
beq $4, 1f
ldq $27, 0($5)
-1: jsr $26, ($27), sys_ni_syscall
+1: ldq $0, 8($sp) /* syscall nr shadow (regs->r1) */
+
+ jsr $26, ($27), sys_ni_syscall
ldgp $gp, 0($26)
blt $0, $syscall_error /* the call failed */
$ret_success:
@@ -509,15 +587,17 @@ ret_to_kernel:
.align 3
$syscall_error:
- /*
- * Some system calls (e.g., ptrace) can return arbitrary
- * values which might normally be mistaken as error numbers.
- * Those functions must zero $0 (v0) directly in the stack
- * frame to indicate that a negative return value wasn't an
- * error number..
- */
- ldq $18, 0($sp) /* old syscall nr (zero if success) */
- beq $18, $ret_success
+/*
+ * Some syscalls (e.g. ptrace) may return negative values that are not
+ * errno. Those syscalls clear the saved syscall number slot (regs->r1)
+ * as a marker; when it is zero, do not convert a negative r0 into errno.
+ */
+
+ ldq $2, 8($sp)
+ beq $2, $ret_success
+
+ /* Restart syscall nr comes from saved r2 (preserved even if r0 overwritten). */
+ ldq $18, 16($sp) /* old syscall nr for restart */
ldq $19, 72($sp) /* .. and this a3 */
subq $31, $0, $0 /* with error in v0 */
@@ -581,6 +661,8 @@ strace:
jsr $26, syscall_trace_enter /* returns the syscall number */
UNDO_SWITCH_STACK
+ stq $0, 8($sp) /* regs->r1 = shadow syscall nr */
+
/* get the arguments back.. */
ldq $16, SP_OFF+24($sp)
ldq $17, SP_OFF+32($sp)
@@ -589,6 +671,11 @@ strace:
ldq $20, 80($sp)
ldq $21, 88($sp)
+ /* nr == -1: internal skip-dispatch or userspace syscall(-1)? */
+ lda $6, -1($31)
+ cmpeq $0, $6, $6
+ bne $6, $strace_skip_call /* nr != -1 => dispatch */
+
/* get the system call pointer.. */
lda $1, NR_syscalls($31)
lda $2, sys_call_table
@@ -607,6 +694,8 @@ $strace_success:
stq $31, 72($sp) /* a3=0 => no error */
stq $0, 0($sp) /* save return value */
+$strace_skip_call:
+ SYSCALL_SKIP_RETURN_RESTART_GATE
DO_SWITCH_STACK
jsr $26, syscall_trace_leave
UNDO_SWITCH_STACK
@@ -614,8 +703,10 @@ $strace_success:
.align 3
$strace_error:
- ldq $18, 0($sp) /* old syscall nr (zero if success) */
- beq $18, $strace_success
+ ldq $2, 8($sp) /* marker: zero means negative isn't errno */
+ beq $2, $strace_success
+ ldq $18, 16($sp) /* restart syscall nr */
+
ldq $19, 72($sp) /* .. and this a3 */
subq $31, $0, $0 /* with error in v0 */
@@ -634,7 +725,7 @@ $strace_error:
mov $31, $26 /* tell "ret_from_sys_call" we can restart */
br ret_from_sys_call
CFI_END_OSF_FRAME entSys
-\f
+
/*
* Save and restore the switch stack -- aka the balance of the user context.
*/
diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index fde4c68e7a0b..0687760ea466 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -16,11 +16,14 @@
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
+#include <linux/seccomp.h>
+#include <asm/syscall.h>
#include <linux/uaccess.h>
#include <asm/fpu.h>
#include "proto.h"
+#include <linux/uio.h>
#define DEBUG DBG_MEM
#undef DEBUG
@@ -312,6 +315,54 @@ long arch_ptrace(struct task_struct *child, long request,
DBG(DBG_MEM, ("poke $%lu<-%#lx\n", addr, data));
ret = put_reg(child, addr, data);
break;
+ case PTRACE_GETREGSET:
+ case PTRACE_SETREGSET: {
+ struct iovec __user *uiov = (struct iovec __user *)data;
+ struct iovec iov;
+ struct pt_regs *regs;
+ size_t len;
+
+ /* Only support NT_PRSTATUS (general registers) for now. */
+ if (addr != NT_PRSTATUS) {
+ ret = -EIO;
+ break;
+ }
+
+ if (copy_from_user(&iov, uiov, sizeof(iov))) {
+ ret = -EFAULT;
+ break;
+ }
+
+ regs = task_pt_regs(child);
+ len = min_t(size_t, iov.iov_len, sizeof(*regs));
+
+ if (request == PTRACE_GETREGSET) {
+ if (copy_to_user(iov.iov_base, regs, len)) {
+ ret = -EFAULT;
+ break;
+ }
+ } else {
+ /*
+ * Allow writing back regs. This is needed by the TRACE_syscall
+ * tests (they change PC/syscall nr/retval).
+ */
+ if (copy_from_user(regs, iov.iov_base, len)) {
+ ret = -EFAULT;
+ break;
+ }
+ }
+
+ /* Per API, update iov_len with amount transferred. */
+ iov.iov_len = len;
+ if (copy_to_user(uiov, &iov, sizeof(iov))) {
+ ret = -EFAULT;
+ break;
+ }
+
+ ret = 0;
+ break;
+ }
+
default:
ret = ptrace_request(child, request, addr, data);
break;
@@ -321,15 +372,37 @@ long arch_ptrace(struct task_struct *child, long request,
asmlinkage unsigned long syscall_trace_enter(void)
{
- unsigned long ret = 0;
struct pt_regs *regs = current_pt_regs();
+
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- ptrace_report_syscall_entry(current_pt_regs()))
- ret = -1UL;
- audit_syscall_entry(regs->r0, regs->r16, regs->r17, regs->r18, regs->r19);
- return ret ?: current_pt_regs()->r0;
+ ptrace_report_syscall_entry(regs)) {
+ syscall_set_nr(current, regs, -1);
+ if (regs->r19 == 0 && regs->r0 == (unsigned long)-1)
+ syscall_set_return_value(current, regs, -ENOSYS, 0);
+ return -1UL;
+ }
+
+ /*
+ * Do the secure computing after ptrace; failures should be fast.
+ * If this fails, seccomp may already have set up the return value
+ * (e.g. SECCOMP_RET_ERRNO / TRACE).
+ */
+ if (secure_computing() == -1) {
+ if (regs->r19 == 0 && regs->r0 == (unsigned long)-1)
+ syscall_set_return_value(current, regs, -ENOSYS, 0);
+ syscall_set_nr(current, regs, -1);
+ return -1UL;
+ }
+
+#ifdef CONFIG_AUDITSYSCALL
+ audit_syscall_entry(syscall_get_nr(current, regs),
+ regs->r16, regs->r17, regs->r18, regs->r19);
+#endif
+ return syscall_get_nr(current, regs);
}
+
+
asmlinkage void
syscall_trace_leave(void)
{
--
2.52.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER
2026-02-20 10:50 [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER Magnus Lindholm
2026-02-20 10:50 ` [PATCH v2 1/1] " Magnus Lindholm
@ 2026-02-24 8:53 ` Michael Cree
1 sibling, 0 replies; 3+ messages in thread
From: Michael Cree @ 2026-02-24 8:53 UTC (permalink / raw)
To: Magnus Lindholm
Cc: richard.henderson, mattst88, linux-kernel, linux-alpha, corbet,
linux-doc, glaubitz, macro, macro, ink
On Fri, Feb 20, 2026 at 11:50:09AM +0100, Magnus Lindholm wrote:
> This patch adds SECCOMP and SECCOMP_FILTER support to the Alpha
> architecture.
>
> The seccomp-bpf selftests exercise syscall tracing, restart, and signal
> interaction paths that were previously untested on Alpha. To support
> these, the ptrace/strace syscall path is updated to reliably distinguish
> internal skip-dispatch from userspace invalid syscall numbers, ensuring
> that syscall(-1) continues to return -ENOSYS with correct r0/a3
> semantics.
>
> Supporting seccomp also requires correct syscall restart handling when
> ptrace and signal delivery are involved. The traced syscall entry path
> now consistently tracks syscall state using r0, r1, and r2 while
> preserving Alpha's a3-based error reporting ABI:
>
> - r1 holds the mutable "current" syscall number
> - r2 preserves the original syscall number for restart
> - r0 and r19 (a3) retain their traditional roles as return value and
> error indicator
>
> This separation allows syscall restarts to be gated strictly on valid
> ERESTART* return codes in the ptrace/strace paths and prevents
> kernel-internal restart values from leaking into userspace.
>
> Alpha also lacked support for PTRACE_GETREGSET(NT_PRSTATUS), causing
> ptrace-based seccomp tests to fail with -EIO. Minimal GETREGSET and
> SETREGSET support is added to export struct pt_regs directly.
>
> With these changes applied, the seccomp-bpf and ptrace syscall selftests
> (seccomp_bpf, extended for Alpha) pass reliably on Alpha systems.
>
> ---
> Changes since v1:
> - Update features documentation for seccomp-filter/alpha
> Link: https://lore.kernel.org/linux-alpha/20260205133049.526-1-linmag7@gmail.com/T/#t
>
> Magnus Lindholm (1):
> alpha: add support for SECCOMP and SECCOMP_FILTER
>
Passes the seccomp-bpf selftests and the live tests of Adrian's
alpha-support branch of libseccomp on my ES45.
Tested-by: Michael Cree <mcree@orcon.net.nz>
Cheers,
Michael.
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2026-02-20 10:50 [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER Magnus Lindholm
2026-02-20 10:50 ` [PATCH v2 1/1] " Magnus Lindholm
2026-02-24 8:53 ` [PATCH v2 0/1] " Michael Cree
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