[PATCH v3 0/4] Clean up hugetlb boot command line processing

[Mike Kravetz]

On 4/20/20 8:34 AM, Qian Cai wrote:
> 
> 
>> On Apr 17, 2020, at 2:50 PM, Mike Kravetz <mike.kravetz at oracle.com> wrote:
>>
>> Longpeng(Mike) reported a weird message from hugetlb command line processing
>> and proposed a solution [1].  While the proposed patch does address the
>> specific issue, there are other related issues in command line processing.
>> As hugetlbfs evolved, updates to command line processing have been made to
>> meet immediate needs and not necessarily in a coordinated manner.  The result
>> is that some processing is done in arch specific code, some is done in arch
>> independent code and coordination is problematic.  Semantics can vary between
>> architectures.
>>
>> The patch series does the following:
>> - Define arch specific arch_hugetlb_valid_size routine used to validate
>>  passed huge page sizes.
>> - Move hugepagesz= command line parsing out of arch specific code and into
>>  an arch independent routine.
>> - Clean up command line processing to follow desired semantics and
>>  document those semantics.
>>
>> [1] https://lore.kernel.org/linux-mm/20200305033014.1152-1-longpeng2@huawei.com
>>
>> Mike Kravetz (4):
>>  hugetlbfs: add arch_hugetlb_valid_size
>>  hugetlbfs: move hugepagesz= parsing to arch independent code
>>  hugetlbfs: remove hugetlb_add_hstate() warning for existing hstate
>>  hugetlbfs: clean up command line processing
> 
> Reverted this series fixed many undefined behaviors on arm64 with the config,
> 
> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> 
> [   54.172683][    T1] UBSAN: shift-out-of-bounds in ./include/linux/hugetlb.h:555:34
> [   54.180411][    T1] shift exponent 4294967285 is too large for 64-bit type 'unsigned long'
> [   54.188885][    T1] CPU: 130 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc2-next-20200420 #1
> [   54.197284][    T1] Hardware name: HPE Apollo 70             /C01_APACHE_MB         , BIOS L50_5.13_1.11 06/18/2019
> [   54.207888][    T1] Call trace:
> [   54.211100][    T1]  dump_backtrace+0x0/0x224
> [   54.215565][    T1]  show_stack+0x20/0x2c
> [   54.219651][    T1]  dump_stack+0xfc/0x184
> [   54.223829][    T1]  __ubsan_handle_shift_out_of_bounds+0x304/0x344
> [   54.230204][    T1]  hugetlb_add_hstate+0x3ec/0x414
> huge_page_size at include/linux/hugetlb.h:555
> (inlined by) hugetlb_add_hstate at mm/hugetlb.c:3301
> [   54.235191][    T1]  hugetlbpage_init+0x14/0x30
> [   54.239824][    T1]  do_one_initcall+0x6c/0x144
> [   54.244446][    T1]  do_initcall_level+0x158/0x1c4
> [   54.249336][    T1]  do_initcalls+0x68/0xb0
> [   54.253597][    T1]  do_basic_setup+0x28/0x30
> [   54.258049][    T1]  kernel_init_freeable+0x19c/0x228
> [   54.263188][    T1]  kernel_init+0x14/0x208
> [   54.267473][    T1]  ret_from_fork+0x10/0x18

While rearranging the code (patch 3 in series), I made the incorrect
assumption that CONT_XXX_SIZE == (1UL << CONT_XXX_SHIFT).  However,
this is not the case.  Does the following patch fix these issues?

>From b75cb4a0852e208bee8c4eb347dc076fcaa88859 Mon Sep 17 00:00:00 2001
From: Mike Kravetz <mike.kravetz at oracle.com>
Date: Mon, 20 Apr 2020 10:41:18 -0700
Subject: [PATCH] arm64/hugetlb: fix hugetlb initialization

When calling hugetlb_add_hstate() to initialize a new hugetlb size,
be sure to use correct huge pages size order.

Signed-off-by: Mike Kravetz <mike.kravetz at oracle.com>
---
 arch/arm64/mm/hugetlbpage.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 9ca840527296..a02411a1f19a 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -453,11 +453,11 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,
 static int __init hugetlbpage_init(void)
 {
 #ifdef CONFIG_ARM64_4K_PAGES
-	hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
+	hugetlb_add_hstate(ilog2(PUD_SIZE) - PAGE_SHIFT);
 #endif
-	hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT);
-	hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
-	hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);
+	hugetlb_add_hstate(ilog2(CONT_PMD_SIZE) - PAGE_SHIFT);
+	hugetlb_add_hstate(ilog2(PMD_SIZE) - PAGE_SHIFT);
+	hugetlb_add_hstate(ilog2(CONT_PTE_SIZE) - PAGE_SHIFT);
 
 	return 0;
 }
-- 
2.25.2