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Date: Mon, 13 Jan 2014 13:32:40 +0800
From: Dave Young <dyoung@...hat.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Linux EFI <linux-efi@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Borislav Petkov <bp@...e.de>,
Arjan van de Ven <arjan@...ux.intel.com>,
Matt Fleming <matt@...sole-pimps.org>,
Matthew Garrett <mjg59@...f.ucam.org>,
"H. Peter Anvin" <hpa@...or.com>, Toshi Kani <toshi.kani@...com>
Subject: Re: [PATCH 1/4] x86, ptdump: Add the functionality to dump an
arbitrary pagetable
On 01/11/14 at 09:49pm, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
>
> With reusing the ->trampoline_pgd page table for mapping EFI regions in
> order to use them after having switched to EFI virtual mode, it is very
> useful to be able to dump aforementioned page table in dmesg. This adds
> that functionality through the walk_pgd_level() interface which can be
> called from somewhere else.
>
> The original functionality of dumping to debugfs remains untouched.
>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
> arch/x86/include/asm/pgtable.h | 3 +-
> arch/x86/mm/dump_pagetables.c | 77 ++++++++++++++++++++++++++++--------------
> 2 files changed, 53 insertions(+), 27 deletions(-)
>
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index bbc8b12fa443..0001851fa785 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -15,9 +15,10 @@
> : (prot))
>
> #ifndef __ASSEMBLY__
> -
> #include <asm/x86_init.h>
>
> +void walk_pgd_level(struct seq_file *m, pgd_t *pgd);
> +
> /*
> * ZERO_PAGE is a global shared page that is always zero: used
> * for zero-mapped memory areas etc..
> diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
> index 0002a3a33081..f987ecff9226 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -19,6 +19,8 @@
>
> #include <asm/pgtable.h>
>
> +static bool dump_to_dmesg;
> +
> /*
> * The dumper groups pagetable entries of the same type into one, and for
> * that it needs to keep some state when walking, and flush this state
> @@ -88,6 +90,24 @@ static struct addr_marker address_markers[] = {
> #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
> #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
>
> +#define pt_dump_seq_printf(m, fmt, args...) \
> +({ \
> + if (dump_to_dmesg) \
> + printk(KERN_INFO fmt, ##args); \
pr_info? This is for debug purpose, maybe pr_debug is better?
Ditto to other printk callbacks.
> + else \
> + if (m) \
> + seq_printf(m, fmt, ##args); \
> +})
> +
> +#define pt_dump_cont_printf(m, fmt, args...) \
> +({ \
> + if (dump_to_dmesg) \
> + printk(KERN_CONT fmt, ##args); \
> + else \
> + if (m) \
> + seq_printf(m, fmt, ##args); \
> +})
> +
> /*
> * Print a readable form of a pgprot_t to the seq_file
> */
> @@ -99,47 +119,47 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level)
>
> if (!pgprot_val(prot)) {
> /* Not present */
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> } else {
> if (pr & _PAGE_USER)
> - seq_printf(m, "USR ");
> + pt_dump_cont_printf(m, "USR ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> if (pr & _PAGE_RW)
> - seq_printf(m, "RW ");
> + pt_dump_cont_printf(m, "RW ");
> else
> - seq_printf(m, "ro ");
> + pt_dump_cont_printf(m, "ro ");
> if (pr & _PAGE_PWT)
> - seq_printf(m, "PWT ");
> + pt_dump_cont_printf(m, "PWT ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> if (pr & _PAGE_PCD)
> - seq_printf(m, "PCD ");
> + pt_dump_cont_printf(m, "PCD ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
>
> /* Bit 9 has a different meaning on level 3 vs 4 */
> if (level <= 3) {
> if (pr & _PAGE_PSE)
> - seq_printf(m, "PSE ");
> + pt_dump_cont_printf(m, "PSE ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> } else {
> if (pr & _PAGE_PAT)
> - seq_printf(m, "pat ");
> + pt_dump_cont_printf(m, "pat ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> }
> if (pr & _PAGE_GLOBAL)
> - seq_printf(m, "GLB ");
> + pt_dump_cont_printf(m, "GLB ");
> else
> - seq_printf(m, " ");
> + pt_dump_cont_printf(m, " ");
> if (pr & _PAGE_NX)
> - seq_printf(m, "NX ");
> + pt_dump_cont_printf(m, "NX ");
> else
> - seq_printf(m, "x ");
> + pt_dump_cont_printf(m, "x ");
> }
> - seq_printf(m, "%s\n", level_name[level]);
> + pt_dump_cont_printf(m, "%s\n", level_name[level]);
> }
>
> /*
> @@ -178,7 +198,7 @@ static void note_page(struct seq_file *m, struct pg_state *st,
> st->current_prot = new_prot;
> st->level = level;
> st->marker = address_markers;
> - seq_printf(m, "---[ %s ]---\n", st->marker->name);
> + pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
> } else if (prot != cur || level != st->level ||
> st->current_address >= st->marker[1].start_address) {
> const char *unit = units;
> @@ -188,16 +208,16 @@ static void note_page(struct seq_file *m, struct pg_state *st,
> /*
> * Now print the actual finished series
> */
> - seq_printf(m, "0x%0*lx-0x%0*lx ",
> - width, st->start_address,
> - width, st->current_address);
> + pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
> + width, st->start_address,
> + width, st->current_address);
>
> delta = (st->current_address - st->start_address) >> 10;
> while (!(delta & 1023) && unit[1]) {
> delta >>= 10;
> unit++;
> }
> - seq_printf(m, "%9lu%c ", delta, *unit);
> + pt_dump_cont_printf(m, "%9lu%c ", delta, *unit);
> printk_prot(m, st->current_prot, st->level);
>
> /*
> @@ -207,7 +227,7 @@ static void note_page(struct seq_file *m, struct pg_state *st,
> */
> if (st->current_address >= st->marker[1].start_address) {
> st->marker++;
> - seq_printf(m, "---[ %s ]---\n", st->marker->name);
> + pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
> }
>
> st->start_address = st->current_address;
> @@ -296,7 +316,7 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
> #define pgd_none(a) pud_none(__pud(pgd_val(a)))
> #endif
>
> -static void walk_pgd_level(struct seq_file *m)
> +void walk_pgd_level(struct seq_file *m, pgd_t *pgd)
How about do not limit to only if (pgd) case, instead do something like below:
set dump_to_dmesg as a module parameter, so user can enable it via kernel cmdline
or set it while insmod.
> {
> #ifdef CONFIG_X86_64
> pgd_t *start = (pgd_t *) &init_level4_pgt;
> @@ -306,6 +326,11 @@ static void walk_pgd_level(struct seq_file *m)
> int i;
> struct pg_state st;
>
> + if (pgd) {
> + start = pgd;
> + dump_to_dmesg = true;
> + }
> +
> memset(&st, 0, sizeof(st));
>
> for (i = 0; i < PTRS_PER_PGD; i++) {
> @@ -331,7 +356,7 @@ static void walk_pgd_level(struct seq_file *m)
>
> static int ptdump_show(struct seq_file *m, void *v)
> {
> - walk_pgd_level(m);
> + walk_pgd_level(m, NULL);
> return 0;
> }
>
> --
> 1.8.5.2.192.g7794a68
>
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