linux-ext4 - [PATCH v15 08/43] x86_64, dept: add support CONFIG_ARCH_HAS_DEPT_SUPPORT to x86

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Message-Id: <20250513100730.12664-9-byungchul@sk.com>
Date: Tue, 13 May 2025 19:06:55 +0900
From: Byungchul Park <byungchul@...com>
To: linux-kernel@...r.kernel.org
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Subject: [PATCH v15 08/43] x86_64, dept: add support CONFIG_ARCH_HAS_DEPT_SUPPORT to x86_64

dept needs to notice every entrance from user to kernel mode to treat
every kernel context independently when tracking wait-event dependencies.
Roughly, system call and user oriented fault are the cases.

Make dept aware of the entrances of x86_64 and add support
CONFIG_ARCH_HAS_DEPT_SUPPORT to x86_64.

Signed-off-by: Byungchul Park <byungchul@...com>
---
 arch/x86/Kconfig            | 1 +
 arch/x86/entry/syscall_64.c | 7 +++++++
 arch/x86/mm/fault.c         | 7 +++++++
 3 files changed, 15 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5873c9e39919..4b6d9e59d96c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -38,6 +38,7 @@ config X86_64
 	select ARCH_HAS_ELFCORE_COMPAT
 	select ZONE_DMA32
 	select EXECMEM if DYNAMIC_FTRACE
+	select ARCH_HAS_DEPT_SUPPORT
 
 config FORCE_DYNAMIC_FTRACE
 	def_bool y
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index b6e68ea98b83..66bd5af5aff1 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -8,6 +8,7 @@
 #include <linux/entry-common.h>
 #include <linux/nospec.h>
 #include <asm/syscall.h>
+#include <linux/dept.h>
 
 #define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
 #define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __x64_##sym(const struct pt_regs *);
@@ -86,6 +87,12 @@ static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
 /* Returns true to return using SYSRET, or false to use IRET */
 __visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr)
 {
+	/*
+	 * This is a system call from user mode.  Make dept work with a
+	 * new kernel mode context.
+	 */
+	dept_update_cxt();
+
 	add_random_kstack_offset();
 	nr = syscall_enter_from_user_mode(regs, nr);
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 296d294142c8..241537ce47fe 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -20,6 +20,7 @@
 #include <linux/mm_types.h>
 #include <linux/mm.h>			/* find_and_lock_vma() */
 #include <linux/vmalloc.h>
+#include <linux/dept.h>
 
 #include <asm/cpufeature.h>		/* boot_cpu_has, ...		*/
 #include <asm/traps.h>			/* dotraplinkage, ...		*/
@@ -1220,6 +1221,12 @@ void do_user_addr_fault(struct pt_regs *regs,
 	tsk = current;
 	mm = tsk->mm;
 
+	/*
+	 * This fault comes from user mode.  Make dept work with a new
+	 * kernel mode context.
+	 */
+	dept_update_cxt();
+
 	if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
 		/*
 		 * Whoops, this is kernel mode code trying to execute from
-- 
2.17.1