linux-kernel - [RFC PATCH 1/6] x86/entry: unify definitions from calling.h and ptrace-abi.h

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Date:   Mon, 10 May 2021 10:45:04 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 1/6] x86/entry: unify definitions from calling.h and ptrace-abi.h

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

The register offsets in <asm/ptrace-abi.h> are duplicated in
entry/calling.h, but are formatted differently and therefore not
compatible. Use the version from <asm/ptrace-abi.h> consistently.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
 arch/x86/entry/calling.h  | 36 +-----------------------------------
 arch/x86/kernel/head_64.S |  6 +++---
 2 files changed, 4 insertions(+), 38 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 07a9331d55e7..7436d4a74ecb 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -6,6 +6,7 @@
 #include <asm/percpu.h>
 #include <asm/asm-offsets.h>
 #include <asm/processor-flags.h>
+#include <asm/ptrace-abi.h>
 
 /*
 
@@ -62,41 +63,6 @@ For 32-bit we have the following conventions - kernel is built with
  * for assembly code:
  */
 
-/* The layout forms the "struct pt_regs" on the stack: */
-/*
- * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
- * unless syscall needs a complete, fully filled "struct pt_regs".
- */
-#define R15		0*8
-#define R14		1*8
-#define R13		2*8
-#define R12		3*8
-#define RBP		4*8
-#define RBX		5*8
-/* These regs are callee-clobbered. Always saved on kernel entry. */
-#define R11		6*8
-#define R10		7*8
-#define R9		8*8
-#define R8		9*8
-#define RAX		10*8
-#define RCX		11*8
-#define RDX		12*8
-#define RSI		13*8
-#define RDI		14*8
-/*
- * On syscall entry, this is syscall#. On CPU exception, this is error code.
- * On hw interrupt, it's IRQ number:
- */
-#define ORIG_RAX	15*8
-/* Return frame for iretq */
-#define RIP		16*8
-#define CS		17*8
-#define EFLAGS		18*8
-#define RSP		19*8
-#define SS		20*8
-
-#define SIZEOF_PTREGS	21*8
-
 .macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
 	.if \save_ret
 	pushq	%rsi		/* pt_regs->si */
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 04bddaaba8e2..d8b3ebd2bb85 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -62,7 +62,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 	 */
 
 	/* Set up the stack for verify_cpu(), similar to initial_stack below */
-	leaq	(__end_init_task - SIZEOF_PTREGS)(%rip), %rsp
+	leaq	(__end_init_task - FRAME_SIZE)(%rip), %rsp
 
 	leaq	_text(%rip), %rdi
 	pushq	%rsi
@@ -343,10 +343,10 @@ SYM_DATA(initial_vc_handler,	.quad handle_vc_boot_ghcb)
 #endif
 
 /*
- * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
+ * The FRAME_SIZE gap is a convention which helps the in-kernel unwinder
  * reliably detect the end of the stack.
  */
-SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - SIZEOF_PTREGS)
+SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - FRAME_SIZE)
 	__FINITDATA
 
 	__INIT
-- 
2.31.1