linux-kernel - [PATCH v2 4/6] x86/entry/32: Convert do_fast_syscall

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Date:   Fri, 21 Jul 2023 12:10:15 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Mika Penttilä <mpenttil@...hat.com>,
        Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 4/6] x86/entry/32: Convert do_fast_syscall_32() to bool return type

Signed-off-by: Brian Gerst <brgerst@...il.com>
---
 arch/x86/entry/common.c          | 10 +++++-----
 arch/x86/entry/entry_32.S        |  2 +-
 arch/x86/entry/entry_64_compat.S |  2 +-
 arch/x86/include/asm/syscall.h   |  4 ++--
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index cccdd18c8304..5b3594457af3 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -220,8 +220,8 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
 	return true;
 }
 
-/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
-__visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
+/* Returns true to return using SYSEXIT/SYSRETL, or false to use IRET */
+__visible noinstr bool do_fast_syscall_32(struct pt_regs *regs)
 {
 	/*
 	 * Called using the internal vDSO SYSENTER/SYSCALL32 calling
@@ -239,7 +239,7 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
 
 	/* Invoke the syscall. If it failed, keep it simple: use IRET. */
 	if (!__do_fast_syscall_32(regs))
-		return 0;
+		return false;
 
 #ifdef CONFIG_X86_64
 	/*
@@ -272,8 +272,8 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
 #endif
 }
 
-/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
-__visible noinstr long do_SYSENTER_32(struct pt_regs *regs)
+/* Returns true to return using SYSEXIT/SYSRETL, or false to use IRET */
+__visible noinstr bool do_SYSENTER_32(struct pt_regs *regs)
 {
 	/* SYSENTER loses RSP, but the vDSO saved it in RBP. */
 	regs->sp = regs->bp;
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 6e6af42e044a..c73047bf9f4b 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -837,7 +837,7 @@ SYM_FUNC_START(entry_SYSENTER_32)
 
 	movl	%esp, %eax
 	call	do_SYSENTER_32
-	testl	%eax, %eax
+	testb	%al, %al
 	jz	.Lsyscall_32_done
 
 	STACKLEAK_ERASE
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index b16272395f1a..27c05d08558a 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -212,7 +212,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
 
 sysret32_from_system_call:
 	/* XEN PV guests always use IRET path */
-	ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
+	ALTERNATIVE "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
 		    "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
 
 	/*
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index be6c5515e0b9..f44e2f9ab65d 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -131,7 +131,7 @@ bool do_syscall_64(struct pt_regs *regs, int nr);
 #endif	/* CONFIG_X86_32 */
 
 void do_int80_syscall_32(struct pt_regs *regs);
-long do_fast_syscall_32(struct pt_regs *regs);
-long do_SYSENTER_32(struct pt_regs *regs);
+bool do_fast_syscall_32(struct pt_regs *regs);
+bool do_SYSENTER_32(struct pt_regs *regs);
 
 #endif	/* _ASM_X86_SYSCALL_H */
-- 
2.41.0