linux-kernel - [RFC PATCH v3 15/32] x86/fred: make unions for the cs and ss fields in struct pt

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Date:   Thu, 23 Feb 2023 23:01:28 -0800
From:   Xin Li <xin3.li@...el.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, peterz@...radead.org,
        andrew.cooper3@...rix.com, seanjc@...gle.com, pbonzini@...hat.com,
        ravi.v.shankar@...el.com
Subject: [RFC PATCH v3 15/32] x86/fred: make unions for the cs and ss fields in struct pt_regs

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Make the cs and ss fields in struct pt_regs unions between the actual
selector and the unsigned long stack slot. FRED uses this space to
store additional flags.

The printk changes are simply due to the cs and ss fields changed to
unsigned short from unsigned long.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
---
 arch/x86/entry/vsyscall/vsyscall_64.c |  2 +-
 arch/x86/include/asm/ptrace.h         | 36 ++++++++++++++++++++++++---
 arch/x86/kernel/process_64.c          |  2 +-
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 4af81df133ee..6349c818d20a 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -76,7 +76,7 @@ static void warn_bad_vsyscall(const char *level, struct pt_regs *regs,
 	if (!show_unhandled_signals)
 		return;
 
-	printk_ratelimited("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
+	printk_ratelimited("%s%s[%d] %s ip:%lx cs:%x sp:%lx ax:%lx si:%lx di:%lx\n",
 			   level, current->comm, task_pid_nr(current),
 			   message, regs->ip, regs->cs,
 			   regs->sp, regs->ax, regs->si, regs->di);
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index f4db78b09c8f..341e44847cc1 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -82,13 +82,41 @@ struct pt_regs {
  * On hw interrupt, it's IRQ number:
  */
 	unsigned long orig_ax;
-/* Return frame for iretq */
+
+	/* Return frame for iretq/eretu/erets */
 	unsigned long ip;
-	unsigned long cs;
+	union {
+		unsigned long  csl; /* CS + any fields above it */
+		struct __attribute__((__packed__)) {
+			unsigned short cs;  /* CS selector proper */
+			unsigned int current_stack_level: 2;
+			unsigned int __csl_resv1	: 6;
+			unsigned int interrupt_shadowed	: 1;
+			unsigned int software_initiated	: 1;
+			unsigned int __csl_resv2	: 2;
+			unsigned int nmi		: 1;
+			unsigned int __csl_resv3	: 3;
+			unsigned int __csl_resv4	: 32;
+		};
+	};
 	unsigned long flags;
 	unsigned long sp;
-	unsigned long ss;
-/* top of stack page */
+	union {
+		unsigned long  ssl; /* SS + any fields above it */
+		struct __attribute__((__packed__)) {
+			unsigned short ss;  /* SS selector proper */
+			unsigned int __ssl_resv1: 16;
+			unsigned int vector	: 8;
+			unsigned int __ssl_resv2: 8;
+			unsigned int type	: 4;
+			unsigned int __ssl_resv3: 4;
+			unsigned int enclv	: 1;
+			unsigned int long_mode	: 1;
+			unsigned int nested	: 1;
+			unsigned int __ssl_resv4: 1;
+			unsigned int instr_len	: 4;
+		};
+	};
 };
 
 #endif /* !__i386__ */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4e34b3b68ebd..57de166dc61c 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -116,7 +116,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
 
 	printk("%sFS:  %016lx(%04x) GS:%016lx(%04x) knlGS:%016lx\n",
 	       log_lvl, fs, fsindex, gs, gsindex, shadowgs);
-	printk("%sCS:  %04lx DS: %04x ES: %04x CR0: %016lx\n",
+	printk("%sCS:  %04x DS: %04x ES: %04x CR0: %016lx\n",
 		log_lvl, regs->cs, ds, es, cr0);
 	printk("%sCR2: %016lx CR3: %016lx CR4: %016lx\n",
 		log_lvl, cr2, cr3, cr4);
-- 
2.34.1