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Message-ID: <20181220184917.GY10600@bombadil.infradead.org>
Date: Thu, 20 Dec 2018 10:49:18 -0800
From: Matthew Wilcox <willy@...radead.org>
To: Igor Stoppa <igor.stoppa@...il.com>
Cc: Andy Lutomirski <luto@...capital.net>,
Peter Zijlstra <peterz@...radead.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>, igor.stoppa@...wei.com,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>, linux-integrity@...r.kernel.org,
kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] __wr_after_init: x86_64: __wr_op
On Wed, Dec 19, 2018 at 11:33:30PM +0200, Igor Stoppa wrote:
> +void *__wr_op(unsigned long dst, unsigned long src, __kernel_size_t len,
> + enum wr_op_type op)
> +{
> + temporary_mm_state_t prev;
> + unsigned long offset;
> + unsigned long wr_poking_addr;
> +
> + /* Confirm that the writable mapping exists. */
> + if (WARN_ONCE(!wr_ready, "No writable mapping available"))
> + return (void *)dst;
> +
> + if (WARN_ONCE(op >= WR_OPS_NUMBER, "Invalid WR operation.") ||
> + WARN_ONCE(!is_wr_after_init(dst, len), "Invalid WR range."))
> + return (void *)dst;
> +
> + offset = dst - (unsigned long)&__start_wr_after_init;
> + wr_poking_addr = wr_poking_base + offset;
> + local_irq_disable();
> + prev = use_temporary_mm(wr_poking_mm);
> +
> + if (op == WR_MEMCPY)
> + copy_to_user((void __user *)wr_poking_addr, (void *)src, len);
> + else if (op == WR_MEMSET)
> + memset_user((void __user *)wr_poking_addr, (u8)src, len);
> +
> + unuse_temporary_mm(prev);
> + local_irq_enable();
> + return (void *)dst;
> +}
I think you're causing yourself more headaches by implementing this "op"
function. Here's some generic code:
void *wr_memcpy(void *dst, void *src, unsigned int len)
{
wr_state_t wr_state;
void *wr_poking_addr = __wr_addr(dst);
local_irq_disable();
wr_enable(&wr_state);
__wr_memcpy(wr_poking_addr, src, len);
wr_disable(&wr_state);
local_irq_enable();
return dst;
}
Now, x86 can define appropriate macros and functions to use the temporary_mm
functionality, and other architectures can do what makes sense to them.
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