Re: [PATCH v2] arm64/traps: Avoid unnecessary kernel/user pointer conversion
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From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-09-17 09:36:48
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On Fri, Sep 17, 2021 at 11:28:11AM +0530, Amit Daniel Kachhap wrote:
Annotating a pointer from kernel to __user and then back again requires an extra __force annotation to silent sparse warning. In call_undef_hook() this unnecessary complexity can be avoided by modifying the intermediate user pointer to unsigned long. This way there is no inter-changeable use of user and kernel pointers and the code is consistent. Note: This patch adds no functional changes to code. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Amit Daniel Kachhap <redacted>
I like that this clarifies that `pc` is not necessarily a user pointer, and this makes the relevant lines shorter and eaier to read, so FWIW: Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks, Mark.
quoted hunk ↗ jump to hunk
--- Changes from v1: * Instead of directly using instruction_pointer() for kernel pointers, modified the pc type from void __user * to unsigned long as suggested by Mark Rutland. arch/arm64/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index b03e383d944a..09236751283e 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c@@ -400,11 +400,11 @@ static int call_undef_hook(struct pt_regs *regs) unsigned long flags; u32 instr; int (*fn)(struct pt_regs *regs, u32 instr) = NULL; - void __user *pc = (void __user *)instruction_pointer(regs); + unsigned long pc = instruction_pointer(regs); if (!user_mode(regs)) { __le32 instr_le; - if (get_kernel_nofault(instr_le, (__force __le32 *)pc)) + if (get_kernel_nofault(instr_le, (__le32 *)pc)) goto exit; instr = le32_to_cpu(instr_le); } else if (compat_thumb_mode(regs)) {-- 2.17.1
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