linux-kernel - Re: [PATCH 1/2] x86/boot/KASLR: Adapt process_e820

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Date:   Tue, 20 Jun 2017 16:22:09 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <keescook@...omium.org>,
        <x86@...nel.org>, <caoj.fnst@...fujitsu.com>,
        <douly.fnst@...fujitsu.com>
Subject: Re: [PATCH 1/2] x86/boot/KASLR: Adapt process_e820_entry for all
 kinds of memory map

On Thu, Jun 15, 2017 at 03:52:48PM +0800, Baoquan He wrote:
>Now function process_e820_entry is only used to process e820 memory
>entry. Adapt it for memory region only, not just for e820. Later
>we will use it to process efi mirror regions.
>
>So rename the original process_e820_entry to process_mem_region, and
>extract and wrap the e820 specific processing code into process_e820_entry.
>
>Signed-off-by: Baoquan He <bhe@...hat.com>

Hi Bao,

Maybe some code annotations should be changed, for example:

	/* Walk e820 and find a random address. */
	random_addr = find_random_phys_addr(min_addr, output_size);

Cause you will walk efi map firstly, and then e820 map(or not).

Thanks,
Chao Fan

>---
> arch/x86/boot/compressed/kaslr.c | 60 ++++++++++++++++++++++------------------
> 1 file changed, 33 insertions(+), 27 deletions(-)
>
>diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>index fe318b4..c2ed051 100644
>--- a/arch/x86/boot/compressed/kaslr.c
>+++ b/arch/x86/boot/compressed/kaslr.c
>@@ -479,35 +479,31 @@ static unsigned long slots_fetch_random(void)
> 	return 0;
> }
> 
>-static void process_e820_entry(struct boot_e820_entry *entry,
>+static void process_mem_region(struct mem_vector *entry,
> 			       unsigned long minimum,
> 			       unsigned long image_size)
> {
> 	struct mem_vector region, overlap;
> 	struct slot_area slot_area;
> 	unsigned long start_orig, end;
>-	struct boot_e820_entry cur_entry;
>-
>-	/* Skip non-RAM entries. */
>-	if (entry->type != E820_TYPE_RAM)
>-		return;
>+	struct mem_vector cur_entry;
> 
> 	/* On 32-bit, ignore entries entirely above our maximum. */
>-	if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= KERNEL_IMAGE_SIZE)
>+	if (IS_ENABLED(CONFIG_X86_32) && entry->start >= KERNEL_IMAGE_SIZE)
> 		return;
> 
> 	/* Ignore entries entirely below our minimum. */
>-	if (entry->addr + entry->size < minimum)
>+	if (entry->start + entry->size < minimum)
> 		return;
> 
> 	/* Ignore entries above memory limit */
>-	end = min(entry->size + entry->addr, mem_limit);
>-	if (entry->addr >= end)
>+	end = min(entry->size + entry->start, mem_limit);
>+	if (entry->start >= end)
> 		return;
>-	cur_entry.addr = entry->addr;
>-	cur_entry.size = end - entry->addr;
>+	cur_entry.start = entry->start;
>+	cur_entry.size = end - entry->start;
> 
>-	region.start = cur_entry.addr;
>+	region.start = cur_entry.start;
> 	region.size = cur_entry.size;
> 
> 	/* Give up if slot area array is full. */
>@@ -522,7 +518,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> 		region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> 
> 		/* Did we raise the address above this e820 region? */
>-		if (region.start > cur_entry.addr + cur_entry.size)
>+		if (region.start > cur_entry.start + cur_entry.size)
> 			return;
> 
> 		/* Reduce size by any delta from the original address. */
>@@ -562,12 +558,31 @@ static void process_e820_entry(struct boot_e820_entry *entry,
> 	}
> }
> 
>-static unsigned long find_random_phys_addr(unsigned long minimum,
>-					   unsigned long image_size)
>+static void process_e820_entry(unsigned long minimum,unsigned long image_size)
> {
> 	int i;
>-	unsigned long addr;
>+	struct mem_vector region;
>+	struct boot_e820_entry *entry;
>+
>+	/* Verify potential e820 positions, appending to slots list. */
>+        for (i = 0; i < boot_params->e820_entries; i++) {
>+                entry = &boot_params->e820_table[i];
>+                /* Skip non-RAM entries. */
>+                if (entry->type != E820_TYPE_RAM)
>+                        continue;
>+                region.start = entry->addr;
>+                region.size = entry->size;
>+                process_mem_region(&region, minimum, image_size);
>+                if (slot_area_index == MAX_SLOT_AREA) {
>+                        debug_putstr("Aborted e820 scan (slot_areas full)!\n");
>+                        break;
>+                }
>+        }
>+}
> 
>+static unsigned long find_random_phys_addr(unsigned long minimum,
>+					   unsigned long image_size)
>+{
> 	/* Check if we had too many memmaps. */
> 	if (memmap_too_large) {
> 		debug_putstr("Aborted e820 scan (more than 4 memmap= args)!\n");
>@@ -577,16 +592,7 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
> 	/* Make sure minimum is aligned. */
> 	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> 
>-	/* Verify potential e820 positions, appending to slots list. */
>-	for (i = 0; i < boot_params->e820_entries; i++) {
>-		process_e820_entry(&boot_params->e820_table[i], minimum,
>-				   image_size);
>-		if (slot_area_index == MAX_SLOT_AREA) {
>-			debug_putstr("Aborted e820 scan (slot_areas full)!\n");
>-			break;
>-		}
>-	}
>-
>+	process_e820_entry(minimum, image_size);
> 	return slots_fetch_random();
> }
> 
>-- 
>2.5.5
>
>
>