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Message-ID: <176173345626.2601451.9394372373920437956.tip-bot2@tip-bot2>
Date: Wed, 29 Oct 2025 10:24:16 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: kernel test robot <lkp@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject:
[tip: core/rseq] ARM: uaccess: Implement missing __get_user_asm_dword()
The following commit has been merged into the core/rseq branch of tip:
Commit-ID: a4354629e7bef36e39ed46139d1f9486fdecf7c9
Gitweb: https://git.kernel.org/tip/a4354629e7bef36e39ed46139d1f9486fdecf7c9
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 27 Oct 2025 09:43:42 +01:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:07 +01:00
ARM: uaccess: Implement missing __get_user_asm_dword()
When CONFIG_CPU_SPECTRE=n then get_user() is missing the 8 byte ASM variant
for no real good reason. This prevents using get_user(u64) in generic code.
Implement it as a sequence of two 4-byte reads with LE/BE awareness and
make the unsigned long (or long long) type for the intermediate variable to
read into dependend on the the target type.
The __long_type() macro and idea was lifted from PowerPC. Thanks to
Christophe for pointing it out.
Closes: https://lore.kernel.org/oe-kbuild-all/202509120155.pFgwfeUD-lkp@intel.com/
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Link: https://patch.msgid.link/20251027083745.168468637@linutronix.de
---
arch/arm/include/asm/uaccess.h | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index f90be31..d6ae80b 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -283,10 +283,17 @@ extern int __put_user_8(void *, unsigned long long);
__gu_err; \
})
+/*
+ * This is a type: either unsigned long, if the argument fits into
+ * that type, or otherwise unsigned long long.
+ */
+#define __long_type(x) \
+ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
+
#define __get_user_err(x, ptr, err, __t) \
do { \
unsigned long __gu_addr = (unsigned long)(ptr); \
- unsigned long __gu_val; \
+ __long_type(x) __gu_val; \
unsigned int __ua_flags; \
__chk_user_ptr(ptr); \
might_fault(); \
@@ -295,6 +302,7 @@ do { \
case 1: __get_user_asm_byte(__gu_val, __gu_addr, err, __t); break; \
case 2: __get_user_asm_half(__gu_val, __gu_addr, err, __t); break; \
case 4: __get_user_asm_word(__gu_val, __gu_addr, err, __t); break; \
+ case 8: __get_user_asm_dword(__gu_val, __gu_addr, err, __t); break; \
default: (__gu_val) = __get_user_bad(); \
} \
uaccess_restore(__ua_flags); \
@@ -353,6 +361,22 @@ do { \
#define __get_user_asm_word(x, addr, err, __t) \
__get_user_asm(x, addr, err, "ldr" __t)
+#ifdef __ARMEB__
+#define __WORD0_OFFS 4
+#define __WORD1_OFFS 0
+#else
+#define __WORD0_OFFS 0
+#define __WORD1_OFFS 4
+#endif
+
+#define __get_user_asm_dword(x, addr, err, __t) \
+ ({ \
+ unsigned long __w0, __w1; \
+ __get_user_asm(__w0, addr + __WORD0_OFFS, err, "ldr" __t); \
+ __get_user_asm(__w1, addr + __WORD1_OFFS, err, "ldr" __t); \
+ (x) = ((u64)__w1 << 32) | (u64) __w0; \
+})
+
#define __put_user_switch(x, ptr, __err, __fn) \
do { \
const __typeof__(*(ptr)) __user *__pu_ptr = (ptr); \
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