linux-um.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: benjamin@sipsolutions.net
To: linux-um@lists.infradead.org
Cc: Benjamin Berg <benjamin@sipsolutions.net>
Subject: [PATCH v2 24/28] um: Add helper functions to get/set state for SECCOMP
Date: Tue, 22 Nov 2022 11:07:55 +0100	[thread overview]
Message-ID: <20221122100759.208290-25-benjamin@sipsolutions.net> (raw)
In-Reply-To: <20221122100759.208290-1-benjamin@sipsolutions.net>

From: Benjamin Berg <benjamin@sipsolutions.net>

When not using ptrace, we need to both save and restore registers
through the mcontext as provided by the host kernel to our signal
handlers.

Add corresponding functions to store the state to an mcontext and
helpers to access the mcontext of the subprocess through the stub data.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
---
 arch/um/include/shared/common-offsets.h |   9 +-
 arch/x86/um/os-Linux/mcontext.c         | 150 +++++++++++++++++++++++-
 arch/x86/um/shared/sysdep/mcontext.h    |   9 ++
 3 files changed, 166 insertions(+), 2 deletions(-)

diff --git a/arch/um/include/shared/common-offsets.h b/arch/um/include/shared/common-offsets.h
index 579ed946a3a9..307dba626001 100644
--- a/arch/um/include/shared/common-offsets.h
+++ b/arch/um/include/shared/common-offsets.h
@@ -28,4 +28,11 @@ DEFINE(UML_CONFIG_64BIT, CONFIG_64BIT);
 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
 DEFINE(UML_CONFIG_UML_TIME_TRAVEL_SUPPORT, CONFIG_UML_TIME_TRAVEL_SUPPORT);
 #endif
-
+#ifdef CONFIG_UML_SECCOMP
+DEFINE(UM_FPSTATE_EXTENDED_SIZE,
+       offsetof(struct _fpstate, sw_reserved)
+       + offsetof(struct _fpx_sw_bytes, extended_size));
+DEFINE(UM_FPSTATE_XSTATE_SIZE,
+       offsetof(struct _fpstate, sw_reserved)
+       + offsetof(struct _fpx_sw_bytes, xstate_size));
+#endif
diff --git a/arch/x86/um/os-Linux/mcontext.c b/arch/x86/um/os-Linux/mcontext.c
index 81b9d1f9f4e6..aabebe58fb25 100644
--- a/arch/x86/um/os-Linux/mcontext.c
+++ b/arch/x86/um/os-Linux/mcontext.c
@@ -1,8 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <sys/ucontext.h>
 #define __FRAME_OFFSETS
 #include <asm/ptrace.h>
 #include <sysdep/ptrace.h>
+#include <string.h>
+#include <signal.h>
+#include <sysdep/mcontext.h>
+#include <linux/errno.h>
+#include <generated/asm-offsets.h>
 
 void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc)
 {
@@ -16,6 +20,10 @@ void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc)
 	COPY2(UESP, ESP); /* sic */
 	COPY(EBX); COPY(EDX); COPY(ECX); COPY(EAX);
 	COPY(EIP); COPY_SEG_CPL3(CS); COPY(EFL); COPY_SEG_CPL3(SS);
+#undef COPY2
+#undef COPY
+#undef COPY_SEG
+#undef COPY_SEG_CPL3
 #else
 #define COPY2(X,Y) regs->gp[X/sizeof(unsigned long)] = mc->gregs[REG_##Y]
 #define COPY(X) regs->gp[X/sizeof(unsigned long)] = mc->gregs[REG_##X]
@@ -27,5 +35,145 @@ void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc)
 	COPY2(EFLAGS, EFL);
 	COPY2(CS, CSGSFS);
 	regs->gp[SS / sizeof(unsigned long)] = mc->gregs[REG_CSGSFS] >> 48;
+#undef COPY2
+#undef COPY
 #endif
 }
+
+#ifdef CONFIG_UML_SECCOMP
+/* Same thing, but the copy macros are turned around. */
+void get_mc_from_regs(struct uml_pt_regs *regs, mcontext_t *mc, int single_stepping)
+{
+#ifdef __i386__
+#define COPY2(X,Y) mc->gregs[REG_##Y] = regs->gp[X]
+#define COPY(X) mc->gregs[REG_##X] = regs->gp[X]
+#define COPY_SEG(X) mc->gregs[REG_##X] = mc->gregs[REG_##X] & 0xffff;
+#define COPY_SEG_CPL3(X) mc->gregs[REG_##X] = (regs->gp[X] & 0xffff) | 3;
+	COPY_SEG(GS); COPY_SEG(FS); COPY_SEG(ES); COPY_SEG(DS);
+	COPY(EDI); COPY(ESI); COPY(EBP);
+	COPY2(UESP, ESP); /* sic */
+	COPY(EBX); COPY(EDX); COPY(ECX); COPY(EAX);
+	COPY(EIP); COPY_SEG_CPL3(CS); COPY(EFL); COPY_SEG_CPL3(SS);
+#else
+#define COPY2(X,Y) mc->gregs[REG_##Y] = regs->gp[X/sizeof(unsigned long)]
+#define COPY(X) mc->gregs[REG_##X] = regs->gp[X/sizeof(unsigned long)]
+	COPY(R8); COPY(R9); COPY(R10); COPY(R11);
+	COPY(R12); COPY(R13); COPY(R14); COPY(R15);
+	COPY(RDI); COPY(RSI); COPY(RBP); COPY(RBX);
+	COPY(RDX); COPY(RAX); COPY(RCX); COPY(RSP);
+	COPY(RIP);
+	COPY2(EFLAGS, EFL);
+	mc->gregs[REG_CSGSFS] = mc->gregs[REG_CSGSFS] & 0xffffffffffffl;
+	mc->gregs[REG_CSGSFS] |= (regs->gp[SS / sizeof(unsigned long)] & 0xffff) << 48;
+#endif
+
+	if (single_stepping)
+		mc->gregs[REG_EFL] |= X86_EFLAGS_TF;
+	else
+		mc->gregs[REG_EFL] &= ~X86_EFLAGS_TF;
+}
+
+int get_stub_state(struct uml_pt_regs *regs, struct stub_data *data)
+{
+	mcontext_t *mcontext;
+	unsigned long fp_regs;
+	int fp_size;
+
+	/* mctx_offset is verified by wait_stub_done_seccomp */
+	mcontext = (void *)&data->sigstack[data->mctx_offset];
+
+	get_regs_from_mc(regs, mcontext);
+
+	/* Assume floating point registers are on the same page */
+	fp_regs = (((unsigned long)mcontext->fpregs &
+		    (UM_KERN_PAGE_SIZE - 1)) +
+		   (unsigned long)&data->sigstack[0]);
+
+	/* Use extended_size, but never touch the trailing magic
+	 * (as it may not fit our internal storage)
+	 */
+	fp_size = *(int *)(fp_regs + UM_FPSTATE_EXTENDED_SIZE)
+		  - FP_XSTATE_MAGIC2_SIZE;
+
+	if (fp_size > sizeof(regs->fp))
+		return -ENOSPC;
+
+	if (fp_regs + fp_size > (unsigned long)data->sigstack +
+				sizeof(data->sigstack))
+		return -EINVAL;
+
+	memcpy(&regs->fp, (void *)fp_regs, fp_size);
+
+	/* We do not need to read the x86_64 FS_BASE/GS_BASE registers as
+	 * we do not permit userspace to set them directly.
+	 */
+
+	return 0;
+}
+
+int set_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+		   int single_stepping)
+{
+	mcontext_t *mcontext;
+	unsigned long fp_regs;
+	int fp_size;
+	int fp_size_stub;
+
+	/* mctx_offset is verified by wait_stub_done_seccomp */
+	mcontext = (void *)&data->sigstack[data->mctx_offset];
+
+	if ((unsigned long)mcontext < (unsigned long)data->sigstack ||
+	    (unsigned long)mcontext >
+			(unsigned long) data->sigstack +
+			sizeof(data->sigstack) - sizeof(*mcontext))
+		return -EINVAL;
+
+	get_mc_from_regs(regs, mcontext, single_stepping);
+
+	/* Assume floating point registers are on the same page */
+	fp_regs = (((unsigned long)mcontext->fpregs &
+		    (UM_KERN_PAGE_SIZE - 1)) +
+		   (unsigned long)&data->sigstack[0]);
+
+	/* Use extended_size, but never touch the trailing magic
+	 * (as it may not fit our internal storage)
+	 */
+	fp_size = *(int *)((unsigned long) &regs->fp +
+			   UM_FPSTATE_EXTENDED_SIZE) -
+		  FP_XSTATE_MAGIC2_SIZE;
+	fp_size_stub = *(int *)(fp_regs + UM_FPSTATE_EXTENDED_SIZE) -
+		       FP_XSTATE_MAGIC2_SIZE;
+
+	/* Can we fit it, or would we need an alternative memory location? */
+	if (fp_size > fp_size_stub)
+		return -ENOSPC;
+
+	if (fp_regs + fp_size > (unsigned long)data->sigstack +
+				sizeof(data->sigstack))
+		return -EINVAL;
+
+	memcpy((void *) fp_regs, &regs->fp, fp_size);
+
+#ifdef __i386__
+	/*
+	 * On x86, we need to sync the GDT entries for the thread local storage.
+	 */
+	#error "Not implemented"
+#else
+	/*
+	 * On x86_64, we need to sync the FS_BASE/GS_BASE registers using the
+	 * arch specific data.
+	 */
+	if (data->arch_data.fs_base != regs->gp[FS_BASE / sizeof(unsigned long)]) {
+		data->arch_data.fs_base = regs->gp[FS_BASE / sizeof(unsigned long)];
+		data->arch_data.sync |= STUB_SYNC_FS_BASE;
+	}
+	if (data->arch_data.gs_base != regs->gp[GS_BASE / sizeof(unsigned long)]) {
+		data->arch_data.gs_base = regs->gp[GS_BASE / sizeof(unsigned long)];
+		data->arch_data.sync |= STUB_SYNC_GS_BASE;
+	}
+#endif
+
+	return 0;
+}
+#endif
diff --git a/arch/x86/um/shared/sysdep/mcontext.h b/arch/x86/um/shared/sysdep/mcontext.h
index b724c54da316..3ea6da0dbe9d 100644
--- a/arch/x86/um/shared/sysdep/mcontext.h
+++ b/arch/x86/um/shared/sysdep/mcontext.h
@@ -6,7 +6,16 @@
 #ifndef __SYS_SIGCONTEXT_X86_H
 #define __SYS_SIGCONTEXT_X86_H
 
+#include <linux/kconfig.h>
+#include <stub-data.h>
+
 extern void get_regs_from_mc(struct uml_pt_regs *, mcontext_t *);
+extern void get_mc_from_regs(struct uml_pt_regs *regs, mcontext_t *mc,
+			     int single_stepping);
+
+extern int get_stub_state(struct uml_pt_regs *regs, struct stub_data *data);
+extern int set_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+			  int single_stepping);
 
 #ifdef __i386__
 
-- 
2.38.1


_______________________________________________
linux-um mailing list
linux-um@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-um

  parent reply	other threads:[~2022-11-22 10:11 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-22 10:07 [PATCH v2 00/28] Implement SECCOMP based userland benjamin
2022-11-22 10:07 ` [PATCH v2 01/28] um: Switch printk calls to adhere to correct coding style benjamin
2022-11-22 10:07 ` [PATCH v2 02/28] um: Declare fix_range_common as a static function benjamin
2022-11-22 10:07 ` [PATCH v2 03/28] um: Drop support for hosts without SYSEMU_SINGLESTEP support benjamin
2022-11-22 10:07 ` [PATCH v2 04/28] um: Drop NULL check from start_userspace benjamin
2022-11-22 10:07 ` [PATCH v2 05/28] um: Make errors to stop ptraced child fatal during startup benjamin
2022-11-22 10:07 ` [PATCH v2 06/28] um: Don't use vfprintf() for os_info() benjamin
2022-11-22 10:07 ` [PATCH v2 07/28] um: Do not use printk in SIGWINCH helper thread benjamin
2022-11-22 10:07 ` [PATCH v2 08/28] um: Reap winch thread if it fails benjamin
2022-11-22 10:07 ` [PATCH v2 09/28] um: Do not use printk in userspace trampoline benjamin
2022-11-22 10:07 ` [PATCH v2 10/28] um: Always inline stub functions benjamin
2022-11-22 10:07 ` [PATCH v2 11/28] um: Rely on PTRACE_SETREGSET to set FS/GS base registers benjamin
2022-11-22 10:07 ` [PATCH v2 12/28] um: Remove unused register save/restore functions benjamin
2022-11-22 10:07 ` [PATCH v2 13/28] um: Mark 32bit syscall helpers as clobbering memory benjamin
2022-11-22 10:07 ` [PATCH v2 14/28] um: Remove stub-data.h include from common-offsets.h benjamin
2022-11-22 10:07 ` [PATCH v2 15/28] um: Create signal stack memory assignment in stub_data benjamin
2022-11-22 10:07 ` [PATCH v2 16/28] um: Add generic stub_syscall6 function benjamin
2022-11-22 10:07 ` [PATCH v2 17/28] um: Rework syscall handling benjamin
2022-11-22 10:07 ` [PATCH v2 18/28] um: Store full CSGSFS and SS register from mcontext benjamin
2022-11-22 10:07 ` [PATCH v2 19/28] um: Pass full mm_id to functions creating helper processes benjamin
2022-11-22 10:07 ` [PATCH v2 20/28] um: Move faultinfo extraction into userspace routine benjamin
2022-11-22 10:07 ` [PATCH v2 21/28] um: Use struct uml_pt_regs for copy_context_skas0 benjamin
2022-11-22 10:07 ` [PATCH v2 22/28] um: Add UML_SECCOMP configuration option benjamin
2022-11-22 10:07 ` [PATCH v2 23/28] um: Add stub side of SECCOMP/futex based process handling benjamin
2022-11-22 10:07 ` benjamin [this message]
2022-11-22 10:07 ` [PATCH v2 25/28] um: Add SECCOMP support detection and initialization benjamin
2022-11-22 10:07 ` [PATCH v2 26/28] um: Die if a child dies unexpectedly in seccomp mode benjamin
2022-11-22 10:07 ` [PATCH v2 27/28] um: Implement kernel side of SECCOMP based process handling benjamin
2022-11-22 10:07 ` [PATCH v2 28/28] um: Delay flushing syscalls until the thread is restarted benjamin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20221122100759.208290-25-benjamin@sipsolutions.net \
    --to=benjamin@sipsolutions.net \
    --cc=linux-um@lists.infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).