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-rw-r--r--patches/source/squashfs-tools/0002-fix_phys_mem_calculation.patch159
1 files changed, 159 insertions, 0 deletions
diff --git a/patches/source/squashfs-tools/0002-fix_phys_mem_calculation.patch b/patches/source/squashfs-tools/0002-fix_phys_mem_calculation.patch
new file mode 100644
index 00000000..20f9005b
--- /dev/null
+++ b/patches/source/squashfs-tools/0002-fix_phys_mem_calculation.patch
@@ -0,0 +1,159 @@
+From 55f7ba830d40d438f0b0663a505e0c227fc68b6b Mon Sep 17 00:00:00 2001
+From: Phillip Lougher <phillip@squashfs.org.uk>
+Date: Tue, 10 Jun 2014 21:51:52 +0100
+Subject: [PATCH] mksquashfs: fix phys mem calculation for 32-bit processes on
+ PAE/64-bit kernels
+
+When adding the code to base default memory usage on physical memory
+(by default use 25% of physical memory), I made an oversight. I assumed
+the process would be able to address 25% of physical memory.
+
+However, for 32-bit processes running on a PAE kernel or 64-bit kernel,
+25% of physical memory can easily exceed the addressible memory for a
+32-bit process, e.g. if a machine has 24 GB of physical memory, the
+code would asume the process could easily use 6 GB.
+
+A 32-bit process by definition can only address 4 GB (32-bit pointers).
+But, due to the typical kernel/user-space split (1GB/3GB, or 2GB/2GB)
+on PAE kernels, a 32-bit process may only be able to address 2 GB.
+
+So, if Mksquashfs is a 32-bit application running on a PAE/64-bit kernel,
+the code assumes it can address much more memory than it really can, which
+means it runs out of memory.
+
+The fix is to impose a maximum default limit on 32-bit kernels, or
+otherwise to never use a value more than 25% of the address space. If
+we assume the maximum address space is 2 GB, then the maximum becomes
+512 MB. But, given most kernels used the 1GB/3GB split, that may be
+unduely conservative, and 25% of 3 GB (756 MB) may be better. This
+patch compromises on 640 MB, which is mid-way between the 512 MB and 756 MB
+values. It is also the fixed default value previously used by Mksquashfs.
+
+This patch also alters the code which imposes a maximum size. Previously
+it was believed limiting to the physical memory size was adequate. But
+obviously this needs to be updated to take into account a 32-bit process
+may only be able to address 2 GB. In the process I've also taken the
+opportunity to limit all requests to no more than 75% of physical memory.
+
+Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
+---
+ squashfs-tools/mksquashfs.c | 78 ++++++++++++++++++++++++++++++++++++++++-----
+ 1 file changed, 70 insertions(+), 8 deletions(-)
+
+diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
+index 86f82bb..5370ecf 100644
+--- a/squashfs-tools/mksquashfs.c
++++ b/squashfs-tools/mksquashfs.c
+@@ -304,7 +304,7 @@ void restorefs();
+ struct dir_info *scan1_opendir(char *pathname, char *subpath, int depth);
+ void write_filesystem_tables(struct squashfs_super_block *sBlk, int nopad);
+ unsigned short get_checksum_mem(char *buff, int bytes);
+-int get_physical_memory();
++void check_usable_phys_mem(int total_mem);
+
+
+ void prep_exit()
+@@ -4053,11 +4053,7 @@ void initialise_threads(int readq, int fragq, int bwriteq, int fwriteq,
+ BAD_ERROR("Queue sizes rediculously too large\n");
+ total_mem += fwriteq;
+
+- if(total_mem > get_physical_memory()) {
+- ERROR("Total queue sizes larger than physical memory.\n");
+- ERROR("Mksquashfs will exhaust physical memory and thrash.\n");
+- BAD_ERROR("Queues too large\n");
+- }
++ check_usable_phys_mem(total_mem);
+
+ /*
+ * convert from queue size in Mbytes to queue size in
+@@ -4879,6 +4875,72 @@ int get_physical_memory()
+ }
+
+
++void check_usable_phys_mem(int total_mem)
++{
++ /*
++ * We want to allow users to use as much of their physical
++ * memory as they wish. However, for practical reasons there are
++ * limits which need to be imposed, to protect users from themselves
++ * and to prevent people from using Mksquashfs as a DOS attack by using
++ * all physical memory. Mksquashfs uses memory to cache data from disk
++ * to optimise performance. It is pointless to ask it to use more
++ * than 75% of physical memory, as this causes thrashing and it is thus
++ * self-defeating.
++ */
++ int mem = get_physical_memory();
++
++ mem = (mem >> 1) + (mem >> 2); /* 75% */
++
++ if(total_mem > mem) {
++ ERROR("Total memory requested is more than 75%% of physical "
++ "memory.\n");
++ ERROR("Mksquashfs uses memory to cache data from disk to "
++ "optimise performance.\n");
++ ERROR("It is pointless to ask it to use more than this amount "
++ "of memory, as this\n");
++ ERROR("causes thrashing and it is thus self-defeating.\n");
++ BAD_ERROR("Requested memory size too large\n");
++ }
++
++ if(sizeof(void *) == 4 && total_mem > 2048) {
++ /*
++ * If we're running on a kernel with PAE or on a 64-bit kernel,
++ * then the 75% physical memory limit can still easily exceed
++ * the addressable memory by this process.
++ *
++ * Due to the typical kernel/user-space split (1GB/3GB, or
++ * 2GB/2GB), we have to conservatively assume the 32-bit
++ * processes can only address 2-3GB. So refuse if the user
++ * tries to allocate more than 2GB.
++ */
++ ERROR("Total memory requested may exceed maximum "
++ "addressable memory by this process\n");
++ BAD_ERROR("Requested memory size too large\n");
++ }
++}
++
++
++int get_default_phys_mem()
++{
++ int mem = get_physical_memory() / SQUASHFS_TAKE;
++
++ if(sizeof(void *) == 4 && mem > 640) {
++ /*
++ * If we're running on a kernel with PAE or on a 64-bit kernel,
++ * the default memory usage can exceed the addressable
++ * memory by this process.
++ * Due to the typical kernel/user-space split (1GB/3GB, or
++ * 2GB/2GB), we have to conservatively assume the 32-bit
++ * processes can only address 2-3GB. So limit the default
++ * usage to 640M, which gives room for other data.
++ */
++ mem = 640;
++ }
++
++ return mem;
++}
++
++
+ void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq,
+ int *fwriteq)
+ {
+@@ -4890,7 +4952,7 @@ void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq,
+
+
+ #define VERSION() \
+- printf("mksquashfs version 4.3 (2014/05/12)\n");\
++ printf("mksquashfs version 4.3-git (2014/06/09)\n");\
+ printf("copyright (C) 2014 Phillip Lougher "\
+ "<phillip@squashfs.org.uk>\n\n"); \
+ printf("This program is free software; you can redistribute it and/or"\
+@@ -4918,7 +4980,7 @@ int main(int argc, char *argv[])
+ int fragq;
+ int bwriteq;
+ int fwriteq;
+- int total_mem = get_physical_memory() / SQUASHFS_TAKE;
++ int total_mem = get_default_phys_mem();
+ int progress = TRUE;
+ int force_progress = FALSE;
+ struct file_buffer **fragment = NULL;