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55b22075f7
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. Tested-by: Michael Cree <mcree@orcon.net.nz> Signed-off-by: Magnus Lindholm <linmag7@gmail.com> Link: https://lore.kernel.org/r/20260409171439.8759-2-linmag7@gmail.com Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_ALPHA_SYSCALL_H
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#define _ASM_ALPHA_SYSCALL_H
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#include <uapi/linux/audit.h>
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#include <linux/audit.h>
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#include <linux/sched.h>
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#include <linux/types.h>
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#include <asm/ptrace.h>
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static inline int syscall_get_arch(struct task_struct *task)
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{
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return AUDIT_ARCH_ALPHA;
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}
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static inline long syscall_get_return_value(struct task_struct *task,
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struct pt_regs *regs)
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{
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return regs->r19 ? -(long)regs->r0 : (long)regs->r0;
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}
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/*
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* Alpha syscall ABI / kernel conventions:
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* - PAL provides syscall number in r0 on entry.
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* - The kernel tracks the active syscall number in regs->r1 (mutable) and
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* preserves the original syscall number in regs->r2 for rollback/restart.
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* - Return value is in regs->r0, with regs->r19 ("a3") as the error flag
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* (0=success, 1=error; on error regs->r0 holds positive errno).
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*/
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static inline long syscall_get_nr(struct task_struct *task,
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struct pt_regs *regs)
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{
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return (long)regs->r1;
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}
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static inline void syscall_set_nr(struct task_struct *task,
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struct pt_regs *regs,
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long nr)
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{
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regs->r1 = (unsigned long)nr;
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}
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/*
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* Syscall arguments:
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* regs->r16..regs->r21 carry up to 6 syscall arguments on entry.
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* Note: regs->r19 is also used as "a3" (error flag) on syscall return.
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*/
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned long *args)
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{
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args[0] = regs->r16;
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args[1] = regs->r17;
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args[2] = regs->r18;
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args[3] = regs->r19;
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args[4] = regs->r20;
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args[5] = regs->r21;
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}
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static inline void syscall_set_arguments(struct task_struct *task,
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struct pt_regs *regs,
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const unsigned long *args)
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{
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regs->r16 = args[0];
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regs->r17 = args[1];
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regs->r18 = args[2];
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regs->r19 = args[3];
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regs->r20 = args[4];
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regs->r21 = args[5];
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}
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/*
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* Set return value for a syscall.
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* Alpha uses r0 for return value and r19 ("a3") as the error indicator:
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* a3 = 0 => success
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* a3 = 1 => error, and userspace interprets r0 as errno (positive).
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*
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* The kernel reports errors to userspace by setting a3=1 and placing a
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* positive errno value in r0. Some syscall paths do this in entry.S,
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* while others (e.g. seccomp/ptrace helpers) use syscall_set_return_value().
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*/
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static inline void syscall_set_return_value(struct task_struct *task,
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struct pt_regs *regs,
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int error, long val)
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{
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if (error) {
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/* error is negative errno in this tree */
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regs->r0 = (unsigned long)(-error); /* positive errno */
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regs->r19 = 1; /* a3 = error */
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} else {
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regs->r0 = (unsigned long)val;
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regs->r19 = 0; /* a3 = success */
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}
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}
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/* Restore the original syscall nr after seccomp/ptrace modified regs->r1. */
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static inline void syscall_rollback(struct task_struct *task,
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struct pt_regs *regs)
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{
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regs->r1 = regs->r2;
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}
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#endif /* _ASM_ALPHA_SYSCALL_H */
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