| Message ID | 20210917055811.22341-1-amit.kachhap@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64/traps: Avoid unnecessary kernel/user pointer conversion | expand |
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 <amit.kachhap@arm.com> 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. > --- > 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 >
On Fri, 17 Sep 2021 11:28:11 +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. > > [...] Applied to arm64 (for-next/misc), thanks! [1/1] arm64/traps: Avoid unnecessary kernel/user pointer conversion https://git.kernel.org/arm64/c/f5b650f887f3 Cheers,
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)) {
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 <amit.kachhap@arm.com> --- 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(-)