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From:   Youling Tang <tangyouling@loongson.cn>
To:     Josh Poimboeuf <jpoimboe@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        madvenka@linux.microsoft.com
Cc:     chenzhongjin@huawei.com, WANG Xuerui <kernel@xen0n.name>,
        Xi Ruoyao <xry111@xry111.site>, live-patching@vger.kernel.org,
        linux-kernel@vger.kernel.org, loongarch@lists.linux.dev,
        tangyouling00@gmail.com, youling.tang@outlook.com,
        Jinyang He <hejinyang@loongson.cn>
Subject: [RFC PATCH v1 19/23] LoongArch: Annotate unwind_hint
Date:   Tue, 20 Jun 2023 15:52:06 +0800
Message-Id: <1687247526-32258-5-git-send-email-tangyouling@loongson.cn>
In-Reply-To: <1687247526-32258-1-git-send-email-tangyouling@loongson.cn>
References: <1687247526-32258-1-git-send-email-tangyouling@loongson.cn>
Precedence: bulk

Some assembly symbols contain code that might be executed with an
unspecified stack state (e.g. invalid stack pointer,no stackframe, ...).

Annotate those symbol with UNWIND_HINT_EMPTY to let objtool be aware of
them.

When taking an exception/interrupt, add UNWIND_HINT_REGS to indicate
from which point the pt_regs is on stack.

Whether returning to userland or creating a new task, sp is
pointing to a pt_regs frame, add UNWIND_HINT_REGS after that.

Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
---
 arch/loongarch/include/asm/stackframe.h | 3 +++
 arch/loongarch/kernel/entry.S           | 2 ++
 arch/loongarch/kernel/head.S            | 1 +
 arch/loongarch/kernel/relocate_kernel.S | 5 +++++
 4 files changed, 11 insertions(+)

diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
index 7df80e6ae9d2..ab16f2d10257 100644
--- a/arch/loongarch/include/asm/stackframe.h
+++ b/arch/loongarch/include/asm/stackframe.h
@@ -13,6 +13,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/loongarch.h>
 #include <asm/thread_info.h>
+#include <asm/unwind_hints.h>
 
 /* Make the addition of cfi info a little easier. */
 	.macro cfi_rel_offset reg offset=0 docfi=0
@@ -158,6 +159,7 @@
 	cfi_st  u0, PT_R21, \docfi
 	csrrd	u0, PERCPU_BASE_KS
 9:
+	UNWIND_HINT_REGS
 	.endm
 
 	.macro	SAVE_ALL docfi=0
@@ -215,6 +217,7 @@
 
 	.macro	RESTORE_SP_AND_RET docfi=0
 	cfi_ld	sp, PT_R3, \docfi
+	UNWIND_HINT_FUNC
 	ertn
 	.endm
 
diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index d737e3cf42d3..458d4e8e126f 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/arch/loongarch/kernel/entry.S
@@ -70,6 +70,7 @@ SYM_FUNC_END(handle_syscall)
 _ASM_NOKPROBE(handle_syscall)
 
 SYM_CODE_START(ret_from_fork)
+	UNWIND_HINT_REGS
 	bl		schedule_tail		# a0 = struct task_struct *prev
 	move		a0, sp
 	bl 		syscall_exit_to_user_mode
@@ -79,6 +80,7 @@ SYM_CODE_START(ret_from_fork)
 SYM_CODE_END(ret_from_fork)
 
 SYM_CODE_START(ret_from_kernel_thread)
+	UNWIND_HINT_REGS
 	bl		schedule_tail		# a0 = struct task_struct *prev
 	move		a0, s1
 	jirl		ra, s0, 0
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index aa64b179744f..73e5ec0006bb 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -43,6 +43,7 @@ SYM_DATA(kernel_offset, .long kernel_offset - _text);
 	.align 12
 
 SYM_CODE_START(kernel_entry)			# kernel entry point
+	UNWIND_HINT_EMPTY
 
 	/* Config direct window and set PG */
 	li.d		t0, CSR_DMW0_INIT	# UC, PLV0, 0x8000 xxxx xxxx xxxx
diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
index d13252553a7c..d0123fa2b511 100644
--- a/arch/loongarch/kernel/relocate_kernel.S
+++ b/arch/loongarch/kernel/relocate_kernel.S
@@ -13,8 +13,11 @@
 #include <asm/loongarch.h>
 #include <asm/stackframe.h>
 #include <asm/addrspace.h>
+#include <asm/unwind_hints.h>
 
 SYM_CODE_START(relocate_new_kernel)
+	UNWIND_HINT_EMPTY
+
 	/*
 	 * a0: EFI boot flag for the new kernel
 	 * a1: Command line pointer for the new kernel
@@ -91,6 +94,8 @@ SYM_CODE_END(relocate_new_kernel)
  * then start at the entry point from LOONGARCH_IOCSR_MBUF0.
  */
 SYM_CODE_START(kexec_smp_wait)
+	UNWIND_HINT_EMPTY
+
 1:	li.w		t0, 0x100			/* wait for init loop */
 2:	addi.w		t0, t0, -1			/* limit mailbox access */
 	bnez		t0, 2b
-- 
2.39.2