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Add ptrace commands used to read/write the XSAVE area of a traced
process. Intended to give debuggers access to xmm/ymm registers. Inspired by FreeBSD which exposes a similar set of ptrace commands. ok kettenis@
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.\" $OpenBSD: ptrace.2,v 1.43 2022/09/11 06:38:11 jmc Exp $
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.\" $OpenBSD: ptrace.2,v 1.44 2024/11/27 05:25:56 anton Exp $
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.\" $NetBSD: ptrace.2,v 1.3 1996/02/23 01:39:41 jtc Exp $
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.\"
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.\" This file is in the public domain.
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.Dd $Mdocdate: September 11 2022 $
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.Dd $Mdocdate: November 27 2024 $
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.Dt PTRACE 2
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.Os
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.Sh NAME
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@ -500,6 +500,58 @@ pointed to by
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The window cookie needs to be
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.Sq XOR'ed
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to stack-saved program counters.
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.It Dv PT_GETXSTATE_INFO Pq amd64 only
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This request can be used to obtain details about the traced process XSAVE area,
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specified in a
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.Dq Li "struct ptrace_xstate_info"
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defined as follows:
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.Bd -literal -offset indent
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struct ptrace_xstate_info {
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uint64_t xsave_mask;
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uint32_t xsave_len;
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};
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.Ed
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.Pp
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The
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.Fa xsave_mask
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field denotes the enabled XSAVE components.
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The
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.Fa xsave_len
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field denotes the size of XSAVE area intended to be used with the
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.Dv PT_GETXSTATE
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and
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.Dv PT_SETXSTATE
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requests.
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.Pp
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A pointer to
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.Dq Li "struct ptrace_xstate_info"
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must be passed in
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.Fa addr
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and the
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.Fa data
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argument must be set to
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.Li sizeof(struct ptrace_xstate_info) .
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.It Dv PT_GETXSTATE Pq amd64 only
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This request can be used to read the XSAVE area of the traced process.
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A pointer to a buffer must be passed in
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.Fa addr
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with a capacity of the length obtained using the
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.Dv PT_GETXSTATE_INFO
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request.
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The
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.Fa data
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argument must reflect the same length.
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.It Dv PT_SETXSTATE Pq amd64 only
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This request can be used to write the XSAVE area of the traced process.
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Only changes to the x87, SSE and AVX state components are honored.
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A pointer to a buffer must be passed in
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.Fa addr
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with a capacity of the length obtained using the
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.Dv PT_GETXSTATE_INFO
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request.
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The
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.Fa data
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argument must reflect the same length.
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.El
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.Sh ERRORS
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Some requests can cause
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@ -579,6 +631,12 @@ An attempt was made to use
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.Dv PT_ATTACH
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on a system process.
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.El
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.It Bq Er ENOTSUP
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.Dv PT_GETXSTATE_INFO ,
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.Dv PT_GETXSTATE ,
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or
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.Dv PT_SETXSTATE
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was attempted on a CPU lacking support for XSAVE.
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.El
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.Sh HISTORY
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The
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@ -1,4 +1,4 @@
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/* $OpenBSD: process_machdep.c,v 1.17 2024/05/13 01:15:50 jsg Exp $ */
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/* $OpenBSD: process_machdep.c,v 1.18 2024/11/27 05:25:56 anton Exp $ */
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/* $NetBSD: process_machdep.c,v 1.1 2003/04/26 18:39:31 fvdl Exp $ */
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/*-
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@ -56,6 +56,7 @@
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/proc.h>
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#include <sys/ptrace.h>
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#include <sys/user.h>
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#include <uvm/uvm_extern.h>
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@ -200,4 +201,84 @@ process_set_pc(struct proc *p, caddr_t addr)
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return (0);
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}
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int
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process_read_xstate_info(struct proc *p, void *addr)
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{
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struct ptrace_xstate_info *info = addr;
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if (xsave_mask == 0)
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return (ENOTSUP);
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info->xsave_mask = xsave_mask;
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info->xsave_len = fpu_save_len;
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return (0);
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}
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struct xsave_area {
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uint8_t legacy_region[512];
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struct xsave_header {
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uint64_t xstate_bv;
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uint64_t xcomp_bv;
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uint8_t rsvd0[48];
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} xsave_header;
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uint8_t extended_region[];
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} __attribute__((packed));
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#define XSTATE_COMPONENT_X87 (1ULL << 0)
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#define XSTATE_COMPONENT_SSE (1ULL << 1)
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#define XSTATE_COMPONENT_AVX (1ULL << 2)
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int
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process_read_xstate(struct proc *p, void *addr)
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{
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struct xsave_area *area =
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(struct xsave_area *)&p->p_addr->u_pcb.pcb_savefpu;
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if (xsave_mask == 0)
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return (ENOTSUP);
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memcpy(addr, area, fpu_save_len);
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return (0);
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}
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int
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process_write_xstate(struct proc *p, void *addr)
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{
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struct xsave_area *area =
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(struct xsave_area *)&p->p_addr->u_pcb.pcb_savefpu;
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struct xsave_area *new_area = (struct xsave_area *)addr;
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uint32_t offset_extended_region = offsetof(struct xsave_area,
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extended_region);
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uint32_t a, b, c, d;
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if (xsave_mask == 0)
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return (ENOTSUP);
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/*
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* Honor changes to x87, SSE and AVX components and mark them as in use.
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* Required to ensure any changes are restored once the traced process
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* continues execution.
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*/
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if ((xsave_mask & XSTATE_COMPONENT_X87) ||
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(xsave_mask & XSTATE_COMPONENT_SSE)) {
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memcpy(area->legacy_region, new_area->legacy_region,
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sizeof(area->legacy_region));
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area->xsave_header.xstate_bv |= xsave_mask &
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(XSTATE_COMPONENT_X87 | XSTATE_COMPONENT_SSE);
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}
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if (xsave_mask & XSTATE_COMPONENT_AVX) {
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CPUID_LEAF(0xd, 2, a, b, c, d);
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if (offset_extended_region == b &&
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offset_extended_region + a <= fpu_save_len) {
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memcpy(area->extended_region,
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new_area->extended_region, a);
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area->xsave_header.xstate_bv |= XSTATE_COMPONENT_AVX;
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}
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}
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return (0);
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}
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#endif /* PTRACE */
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@ -1,4 +1,4 @@
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/* $OpenBSD: ptrace.h,v 1.1 2004/01/28 01:39:39 mickey Exp $ */
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/* $OpenBSD: ptrace.h,v 1.2 2024/11/27 05:25:57 anton Exp $ */
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/* $NetBSD: ptrace.h,v 1.1 2003/04/26 18:39:47 fvdl Exp $ */
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/*
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@ -39,3 +39,18 @@
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#define PT_SETREGS (PT_FIRSTMACH + 2)
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#define PT_GETFPREGS (PT_FIRSTMACH + 3)
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#define PT_SETFPREGS (PT_FIRSTMACH + 4)
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#define PT_GETXSTATE_INFO (PT_FIRSTMACH + 5)
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#define PT_GETXSTATE (PT_FIRSTMACH + 6)
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#define PT_SETXSTATE (PT_FIRSTMACH + 7)
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struct ptrace_xstate_info {
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uint64_t xsave_mask;
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uint32_t xsave_len;
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};
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#ifdef _KERNEL
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int process_read_xstate_info(struct proc *, void *);
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int process_read_xstate(struct proc *, void *);
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int process_write_xstate(struct proc *, void *);
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#endif
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@ -1,4 +1,4 @@
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/* $OpenBSD: sys_process.c,v 1.102 2024/10/08 12:02:24 claudio Exp $ */
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/* $OpenBSD: sys_process.c,v 1.103 2024/11/27 05:25:57 anton Exp $ */
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/* $NetBSD: sys_process.c,v 1.55 1996/05/15 06:17:47 tls Exp $ */
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/*-
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@ -66,6 +66,7 @@
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#include <uvm/uvm_extern.h>
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#include <machine/fpu.h>
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#include <machine/reg.h>
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#ifdef PTRACE
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@ -206,6 +207,24 @@ sys_ptrace(struct proc *p, void *v, register_t *retval)
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mode = OUT;
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size = sizeof u.u_pacmask;
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break;
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#endif
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#ifdef PT_GETXSTATE_INFO
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case PT_GETXSTATE_INFO:
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mode = OUT_ALLOC;
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size = sizeof(struct ptrace_xstate_info);
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break;
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#endif
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#ifdef PT_GETXSTATE
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case PT_GETXSTATE:
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mode = OUT_ALLOC;
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size = fpu_save_len;
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break;
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#endif
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#ifdef PT_SETXSTATE
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case PT_SETXSTATE:
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mode = IN_ALLOC;
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size = fpu_save_len;
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break;
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#endif
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default:
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return EINVAL;
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@ -759,6 +778,18 @@ ptrace_ustate(struct proc *p, int req, pid_t pid, void *addr, int data,
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((register_t *)addr)[0] = process_get_pacmask(t);
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((register_t *)addr)[1] = process_get_pacmask(t);
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return 0;
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#endif
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#ifdef PT_GETXSTATE_INFO
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case PT_GETXSTATE_INFO:
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return process_read_xstate_info(t, addr);
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#endif
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#ifdef PT_GETXSTATE
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case PT_GETXSTATE:
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return process_read_xstate(t, addr);
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#endif
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#ifdef PT_SETXSTATE
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case PT_SETXSTATE:
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return process_write_xstate(t, addr);
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#endif
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default:
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KASSERTMSG(0, "%s: unhandled request %d", __func__, req);
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