Sohil Mehta b36d1f53d9 x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE ... The EMULATE mode of vsyscall maps the vsyscall page with a high kernel address directly into user address space. Reading the vsyscall page in EMULATE mode would cause LASS to trigger a #GP. Fixing the LASS violation in EMULATE mode would require complex instruction decoding because the resulting #GP does include the necessary error information, and the vsyscall address is not readily available in the RIP. The EMULATE mode has been deprecated since 2022 and can only be enabled using the command line parameter vsyscall=emulate. See commit bf00745e77 ("x86/vsyscall: Remove CONFIG_LEGACY_VSYSCALL_EMULATE") for details. At this point, no one is expected to be using this insecure mode. The rare usages that need it obviously do not care about security. Disable LASS when EMULATE mode is requested to avoid breaking legacy user software. Also, update the vsyscall documentation to reflect this. LASS will only be supported if vsyscall mode is set to XONLY (default) or NONE. Signed-off-by: Sohil Mehta <sohil.mehta@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com> Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> Link: https://patch.msgid.link/20260309181029.398498-5-sohil.mehta@intel.com		2026-03-19 15:11:13 -07:00
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Makefile	x86/vdso: Switch to generic vDSO implementation	2019-06-22 21:21:10 +02:00
vsyscall_64.c	x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE	2026-03-19 15:11:13 -07:00
vsyscall_emu_64.S	x86/vsyscall_emu/64: Don't use RET in vsyscall emulation	2022-06-27 10:33:58 +02:00
vsyscall_trace.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00