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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 2/9] x86: Simplify compat syscall userspace allocation
Date: Thu,  1 Oct 2020 16:58:12 -0400	[thread overview]
Message-ID: <20201001205819.27879-3-krisman@collabora.com> (raw)
In-Reply-To: <20201001205819.27879-1-krisman@collabora.com>

When allocating user memory space for a compat system call, don't
consider whether the originating code is IA32 or X32, just allocate from
a safe region for both, beyond the redzone.  This should be safe for
IA32, and has the benefit of avoiding TIF_IA32, which we want to drop.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 arch/x86/include/asm/compat.h | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index d4edf281fff4..a4b5126dff4e 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -179,14 +179,13 @@ typedef struct user_regs_struct compat_elf_gregset_t;
 
 static inline void __user *arch_compat_alloc_user_space(long len)
 {
-	compat_uptr_t sp;
-
-	if (test_thread_flag(TIF_IA32)) {
-		sp = task_pt_regs(current)->sp;
-	} else {
-		/* -128 for the x32 ABI redzone */
-		sp = task_pt_regs(current)->sp - 128;
-	}
+	compat_uptr_t sp = task_pt_regs(current)->sp;
+
+	/*
+	 * -128 for the x32 ABI redzone.  For IA32, it is not strictly
+	 * necessary, but not harmful.
+	 */
+	sp -= 128;
 
 	return (void __user *)round_down(sp - len, 16);
 }
-- 
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 ` Gabriel Krisman Bertazi [this message]
2020-10-01 20:58 ` [PATCH v2 3/9] x86: oprofile: " 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 ` [PATCH v2 5/9] x86: elf: Use e_machine to select start_thread for x32 Gabriel Krisman Bertazi
2020-10-01 21:49   ` 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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