# git rev-parse -q --verify 2d4f9bdc22740d10984b850bdd74a86ad8ed3d23^{commit}
2d4f9bdc22740d10984b850bdd74a86ad8ed3d23
already have revision, skipping fetch
# git checkout -q -f -B kisskb 2d4f9bdc22740d10984b850bdd74a86ad8ed3d23
# git clean -qxdf
# < git log -1
# commit 2d4f9bdc22740d10984b850bdd74a86ad8ed3d23
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Tue May 14 23:00:58 2019 +1000
# 
#     powerpc/mm: Fix crashes with hugepages & 4K pages
#     
#     The recent commit to cleanup ifdefs in the hugepage initialisation led
#     to crashes when using 4K pages as reported by Sachin:
#     
#       BUG: Kernel NULL pointer dereference at 0x0000001c
#       Faulting instruction address: 0xc000000001d1e58c
#       Oops: Kernel access of bad area, sig: 11 [#1]
#       LE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
#       ...
#       CPU: 3 PID: 4635 Comm: futex_wake04 Tainted: G        W  O      5.1.0-next-20190507-autotest #1
#       NIP:  c000000001d1e58c LR: c000000001d1e54c CTR: 0000000000000000
#       REGS: c000000004937890 TRAP: 0300
#       MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 22424822  XER: 00000000
#       CFAR: c00000000183e9e0 DAR: 000000000000001c DSISR: 40000000 IRQMASK: 0
#       ...
#       NIP kmem_cache_alloc+0xbc/0x5a0
#       LR  kmem_cache_alloc+0x7c/0x5a0
#       Call Trace:
#         huge_pte_alloc+0x580/0x950
#         hugetlb_fault+0x9a0/0x1250
#         handle_mm_fault+0x490/0x4a0
#         __do_page_fault+0x77c/0x1f00
#         do_page_fault+0x28/0x50
#         handle_page_fault+0x18/0x38
#     
#     This is caused by us trying to allocate from a NULL kmem cache in
#     __hugepte_alloc(). The kmem cache is NULL because it was never
#     allocated in hugetlbpage_init(), because add_huge_page_size() returned
#     an error.
#     
#     The reason add_huge_page_size() returned an error is a simple typo, we
#     are calling check_and_get_huge_psize(size) when we should be passing
#     shift instead.
#     
#     The fact that we're able to trigger this path when the kmem caches are
#     NULL is a separate bug, ie. we should not advertise any hugepage sizes
#     if we haven't setup the required caches for them.
#     
#     This was only seen with 4K pages, with 64K pages we don't need to
#     allocate any extra kmem caches because the 16M hugepage just occupies
#     a single entry at the PMD level.
#     
#     Fixes: 723f268f19da ("powerpc/mm: cleanup ifdef mess in add_huge_page_size()")
#     Reported-by: Sachin Sant <sachinp@linux.ibm.com>
#     Tested-by: Sachin Sant <sachinp@linux.ibm.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 2d4f9bdc22740d10984b850bdd74a86ad8ed3d23
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64e_defconfig
# Added to kconfig CONFIG_SMP=n
# yes \n | make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  oldconfig
yes: standard output: Broken pipe
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
<stdin>:1388:2: warning: #warning syscall open_tree not implemented [-Wcpp]
<stdin>:1391:2: warning: #warning syscall move_mount not implemented [-Wcpp]
<stdin>:1394:2: warning: #warning syscall fsopen not implemented [-Wcpp]
<stdin>:1397:2: warning: #warning syscall fsconfig not implemented [-Wcpp]
<stdin>:1400:2: warning: #warning syscall fsmount not implemented [-Wcpp]
<stdin>:1403:2: warning: #warning syscall fspick not implemented [-Wcpp]
WARNING: vmlinux.o(.text+0x39e): Section mismatch in reference from the variable start_here_multiplatform to the function .init.text:.early_setup()
The function start_here_multiplatform() references
the function __init .early_setup().
This is often because start_here_multiplatform lacks a __init 
annotation or the annotation of .early_setup is wrong.

INFO: Uncompressed kernel (size 0xbd6b98) overlaps the address of the wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0xc00000)
Image Name:   Linux-5.1.0-g2d4f9bdc2274
Created:      Wed May 15 04:45:17 2019
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    5071425 Bytes = 4952.56 KiB = 4.84 MiB
Load Address: 00000000
Entry Point:  00000000
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_ppc64e_defconfig+UP_powerpc-gcc5
# Build took: 0:01:30.488914