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From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: luto@kernel.org, tglx@linutronix.de
Cc: hch@lst.de, hpa@zytor.com, bp@alien8.de, rric@kernel.org,
	peterz@infradead.org, mingo@redhat.com, x86@kernel.org,
	linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	kernel@collabora.com
Subject: [PATCH v2 5/9] x86: elf: Use e_machine to select start_thread for x32
Date: Thu,  1 Oct 2020 16:58:15 -0400	[thread overview]
Message-ID: <20201001205819.27879-6-krisman@collabora.com> (raw)
In-Reply-To: <20201001205819.27879-1-krisman@collabora.com>

Since TIF_X32 is going away, avoid using it to find the ELF type on
compat_start_thread

According to SysV AMD64 ABI Draft, an AMD64 ELF object using ILP32 must
have ELFCLASS32 with (E_MACHINE == EM_X86_64), so use that ELF field to
differentiate a x32 object from a IA32 object when executing
start_thread in compat mode.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 arch/x86/include/asm/elf.h   | 11 +++++++++--
 arch/x86/kernel/process_64.c | 11 +++++++----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 9220efc65d78..33c1c9be2e07 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -186,8 +186,15 @@ static inline void elf_common_init(struct thread_struct *t,
 #define	COMPAT_ELF_PLAT_INIT(regs, load_addr)		\
 	elf_common_init(&current->thread, regs, __USER_DS)
 
-void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp);
-#define compat_start_thread compat_start_thread
+void compat_start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp);
+void compat_start_thread_x32(struct pt_regs *regs, u32 new_ip, u32 new_sp);
+#define compat_start_thread(regs, new_ip, new_sp)			\
+do {									\
+	if (elf_ex->e_machine == EM_X86_64)				\
+		compat_start_thread_x32(regs, new_ip, new_sp);		\
+	else								\
+		compat_start_thread_ia32(regs, new_ip, new_sp);		\
+} while (0)
 
 void set_personality_ia32(bool);
 #define COMPAT_SET_PERSONALITY(ex)			\
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9afefe325acb..56e882c339e6 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -511,12 +511,15 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 EXPORT_SYMBOL_GPL(start_thread);
 
 #ifdef CONFIG_COMPAT
-void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp)
+void compat_start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp)
 {
 	start_thread_common(regs, new_ip, new_sp,
-			    test_thread_flag(TIF_X32)
-			    ? __USER_CS : __USER32_CS,
-			    __USER_DS, __USER_DS);
+			    __USER32_CS, __USER_DS, __USER_DS);
+}
+void compat_start_thread_x32(struct pt_regs *regs, u32 new_ip, u32 new_sp)
+{
+	start_thread_common(regs, new_ip, new_sp,
+			    __USER_CS, __USER_DS, __USER_DS);
 }
 #endif
 
-- 
2.28.0


  parent reply	other threads:[~2020-10-01 20:59 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01 20:58 [PATCH v2 0/9] Reclaim TIF_IA32 and TIF_X32 Gabriel Krisman Bertazi
2020-10-01 20:58 ` [PATCH v2 1/9] x86: events: Avoid TIF_IA32 when checking 64bit mode Gabriel Krisman Bertazi
2020-10-01 20:58 ` [PATCH v2 2/9] x86: Simplify compat syscall userspace allocation Gabriel Krisman Bertazi
2020-10-01 20:58 ` [PATCH v2 3/9] x86: oprofile: Avoid TIF_IA32 when checking 64bit mode Gabriel Krisman Bertazi
2020-10-01 20:58 ` [PATCH v2 4/9] x86: elf: Use e_machine to choose DLINFO in compat Gabriel Krisman Bertazi
2020-10-01 21:46   ` Andy Lutomirski
2020-10-01 20:58 ` Gabriel Krisman Bertazi [this message]
2020-10-01 21:49   ` [PATCH v2 5/9] x86: elf: Use e_machine to select start_thread for x32 Andy Lutomirski
2020-10-01 20:58 ` [PATCH v2 6/9] x86: elf: Use e_machine to select setup_additional_pages " Gabriel Krisman Bertazi
2020-10-01 21:50   ` Andy Lutomirski
2020-10-01 20:58 ` [PATCH v2 7/9] x86: Use current USER_CS to setup correct context on vmx entry Gabriel Krisman Bertazi
2020-10-01 21:52   ` Andy Lutomirski
2020-10-02 22:40     ` Sean Christopherson
2020-10-02 23:11       ` Gabriel Krisman Bertazi
2020-10-03  0:15       ` Andy Lutomirski
2020-10-03 23:04         ` Andy Lutomirski
2020-10-05 18:56           ` Andy Lutomirski
2020-10-05 19:54           ` Sean Christopherson
2020-10-01 20:58 ` [PATCH v2 8/9] x86: Convert mmu context ia32_compat into a proper flags field Gabriel Krisman Bertazi
2020-10-01 22:09   ` Andy Lutomirski
2020-10-01 20:58 ` [PATCH v2 9/9] x86: Reclaim TIF_IA32 and TIF_X32 Gabriel Krisman Bertazi

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