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Message-ID: <20160930003627.GB4369@remoulade>
Date: Fri, 30 Sep 2016 01:36:28 +0100
From: Mark Rutland <mark.rutland@....com>
To: Laura Abbott <labbott@...hat.com>
Cc: AKASHI Takahiro <takahiro.akashi@...aro.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
David Brown <david.brown@...aro.org>,
Will Deacon <will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Kees Cook <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 2/3] arm64: dump: Make the page table dumping seq_file
optional
On Thu, Sep 29, 2016 at 02:32:56PM -0700, Laura Abbott wrote:
> The page table dumping code always assumes it will be dumping to a
> seq_file to userspace. The dumping code is useful in other situations.
> Let the seq_file be optional.
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
It might be worth elaborating on those other situations, e.g. that for those
we'll have some additional logic that will only run in the absence of a
seq_file.
The NOPing out of logic in the !seq_file case does feel a bit like spaghetti
code, but it's not obvious to me that adding finer-grained callbacks is much
better, and I guess we can reconsider that if and when we need to add more
logic.
Regardless of the above:
Acked-by: Mark Rutland <mark.rutland@....com>
Thanks,
Mark.
> ---
> arch/arm64/mm/dump.c | 26 +++++++++++++++++++-------
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 29e0838..e318f3d 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -50,6 +50,18 @@ static const struct addr_marker address_markers[] = {
> { -1, NULL },
> };
>
> +#define pt_dump_seq_printf(m, fmt, args...) \
> +({ \
> + if (m) \
> + seq_printf(m, fmt, ##args); \
> +})
> +
> +#define pt_dump_seq_puts(m, fmt) \
> +({ \
> + if (m) \
> + seq_printf(m, fmt); \
> +})
> +
> /*
> * The page dumper groups page table entries of the same type into a single
> * description. It uses pg_state to track the range information while
> @@ -186,7 +198,7 @@ static void dump_prot(struct pg_state *st, const struct prot_bits *bits,
> s = bits->clear;
>
> if (s)
> - seq_printf(st->seq, " %s", s);
> + pt_dump_seq_printf(st->seq, " %s", s);
> }
> }
>
> @@ -200,14 +212,14 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> st->level = level;
> st->current_prot = prot;
> st->start_address = addr;
> - seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> } else if (prot != st->current_prot || level != st->level ||
> addr >= st->marker[1].start_address) {
> const char *unit = units;
> unsigned long delta;
>
> if (st->current_prot) {
> - seq_printf(st->seq, "0x%016lx-0x%016lx ",
> + pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx ",
> st->start_address, addr);
>
> delta = (addr - st->start_address) >> 10;
> @@ -215,17 +227,17 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> delta >>= 10;
> unit++;
> }
> - seq_printf(st->seq, "%9lu%c %s", delta, *unit,
> + pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
> pg_level[st->level].name);
> if (pg_level[st->level].bits)
> dump_prot(st, pg_level[st->level].bits,
> pg_level[st->level].num);
> - seq_puts(st->seq, "\n");
> + pt_dump_seq_puts(st->seq, "\n");
> }
>
> if (addr >= st->marker[1].start_address) {
> st->marker++;
> - seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> }
>
> st->start_address = addr;
> @@ -235,7 +247,7 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
>
> if (addr >= st->marker[1].start_address) {
> st->marker++;
> - seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> }
>
> }
> --
> 2.10.0
>
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