From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ravi Shankar <ravi.v.shankar@intel.com>,
Tony Luck <tony.luck@intel.com>,
Sohil Mehta <sohil.mehta@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Subject: [PATCH v3 03/12] x86/alternatives: Disable LASS when patching kernel alternatives
Date: Fri, 9 Jun 2023 21:36:23 +0300 [thread overview]
Message-ID: <20230609183632.48706-4-alexander.shishkin@linux.intel.com> (raw)
In-Reply-To: <20230609183632.48706-1-alexander.shishkin@linux.intel.com>
From: Sohil Mehta <sohil.mehta@intel.com>
For patching, the kernel initializes a temporary mm area in the lower
half of the address range. See commit 4fc19708b165 ("x86/alternatives:
Initialize temporary mm for patching").
Disable LASS enforcement during patching using the stac()/clac()
instructions to avoid triggering a #GP fault.
The objtool warns due to a call to a non-allowed function that exists
outside of the stac/clac guard, or references to any function with a
dynamic function pointer inside the guard. See the Objtool warnings
section #9 in the document tools/objtool/Documentation/objtool.txt.
Considering that patching is usually small, replace the memcpy and
memset functions in the text poking functions with their inline versions
respectively.
Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
arch/x86/kernel/alternative.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index f615e0cb6d93..eac6a5406d39 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1526,16 +1526,24 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
__ro_after_init struct mm_struct *poking_mm;
__ro_after_init unsigned long poking_addr;
+/*
+ * poking_init() initializes the text poking address from the lower half of the
+ * address space. Relax LASS enforcement when accessing the poking address.
+ */
static void text_poke_memcpy(void *dst, const void *src, size_t len)
{
- memcpy(dst, src, len);
+ stac();
+ __inline_memcpy(dst, src, len);
+ clac();
}
static void text_poke_memset(void *dst, const void *src, size_t len)
{
int c = *(const int *)src;
- memset(dst, c, len);
+ stac();
+ __inline_memset(dst, c, len);
+ clac();
}
typedef void text_poke_f(void *dst, const void *src, size_t len);
--
2.39.2
next prev parent reply other threads:[~2023-06-09 18:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 18:36 [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 01/12] x86/cpu: Enumerate the LASS feature bits Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 02/12] x86/asm: Introduce inline memcpy and memset Alexander Shishkin
2023-06-09 18:36 ` Alexander Shishkin [this message]
2023-07-31 22:41 ` [PATCH v3 03/12] x86/alternatives: Disable LASS when patching kernel alternatives Edgecombe, Rick P
2023-08-01 21:10 ` Sohil Mehta
2023-08-01 21:50 ` Edgecombe, Rick P
2023-06-09 18:36 ` [PATCH v3 04/12] x86/cpu: Enable LASS during CPU initialization Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 05/12] x86/cpu: Remove redundant comment during feature setup Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 06/12] x86/vsyscall: Reorganize the #PF emulation code Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 07/12] x86/traps: Consolidate user fixups in exc_general_protection() Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 08/12] x86/vsyscall: Add vsyscall emulation for #GP Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 09/12] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 11/12] x86/cpu: Set LASS CR4 bit as pinning sensitive Alexander Shishkin
2023-06-09 18:36 ` [RFC v3 12/12] x86/efi: Disable LASS enforcement when switching to EFI MM Alexander Shishkin
2023-07-31 18:00 ` [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-07-31 22:36 ` Edgecombe, Rick P
2023-08-01 19:50 ` Sohil Mehta
2023-08-01 20:38 ` Edgecombe, Rick P
2023-08-04 23:52 ` Edgecombe, Rick P
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