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Subject[PATCH V2 00/17] riscv: compat: Add COMPAT mode support for rv64
Date
From: Guo Ren <guoren@linux.alibaba.com>

Currently, most 64-bit architectures (x86, parisc, powerpc, arm64,
s390, mips, sparc) have supported COMPAT mode. But they all have
history issues and can't use standard linux unistd.h. RISC-V would
be first standard __SYSCALL_COMPAT user of include/uapi/asm-generic
/unistd.h.

The patchset are based on v5.16-rc6, you can compare rv64-compat32
v.s. rv32-whole in qemu with following step:

- Prepare rv32 rootfs & fw_jump.bin by buildroot.org
$ git clone git://git.busybox.net/buildroot
$ cd buildroot
$ make qemu_riscv32_virt_defconfig O=qemu_riscv32_virt_defconfig
$ make -C qemu_riscv32_virt_defconfig
$ make qemu_riscv64_virt_defconfig O=qemu_riscv64_virt_defconfig
$ make -C qemu_riscv64_virt_defconfig
(Got fw_jump.bin & rootfs.ext2 in qemu_riscvXX_virt_defconfig/images)

- Prepare Linux rv32 & rv64 Image
$ git clone git@github.com:c-sky/csky-linux.git -b riscv_compat_v2 linux
$ cd linux
$ echo "CONFIG_STRICT_KERNEL_RWX=n" >> arch/riscv/configs/defconfig
$ echo "CONFIG_STRICT_MODULE_RWX=n" >> arch/riscv/configs/defconfig
$ make ARCH=riscv CROSS_COMPILE=riscv32-buildroot-linux-gnu- O=../build-rv32/ rv32_defconfig
$ make ARCH=riscv CROSS_COMPILE=riscv32-buildroot-linux-gnu- O=../build-rv32/ Image
$ make ARCH=riscv CROSS_COMPILE=riscv64-buildroot-linux-gnu- O=../build-rv64/ defconfig
$ make ARCH=riscv CROSS_COMPILE=riscv64-buildroot-linux-gnu- O=../build-rv64/ Image

- Prepare Qemu: (made by LIU Zhiwei <zhiwei_liu@c-sky.com>)
$ git clone https://github.com/romanheros/qemu.git -b riscv-upstream-uxl-v5
$ cd qemu
$ ./configure --target-list="riscv64-softmmu riscv32-softmmu"
$ make

- Run rv64 with rv32 rootfs in compat mode:
$ ./build/qemu-system-riscv64 -cpu rv64,x-h=true -M virt -m 64m -nographic -bios qemu_riscv64_virt_defconfig/images/fw_jump.bin -kernel build-rv64/Image -drive file qemu_riscv32_virt_defconfig/images/rootfs.ext2,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 -append "rootwait root=/dev/vda ro console=ttyS0 earlycon=sbi" -netdev user,id=net0 -device virtio-net-device,netdev=net0

QEMU emulator version 6.2.50 (v6.2.0-29-g196d7182c8)
OpenSBI v0.9
[ 0.000000] Linux version 5.16.0-rc6-00017-g750f87086bdd-dirty (guoren@guoren-Z87-HD3) (riscv64-unknown-linux-gnu-gcc (GCC) 10.2.0, GNU ld (GNU Binutils) 2.37) #96 SMP Tue Dec 28 21:01:55 CST 2021
[ 0.000000] OF: fdt: Ignoring memory range 0x80000000 - 0x80200000
[ 0.000000] Machine model: riscv-virtio,qemu
[ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[ 0.000000] printk: bootconsole [sbi0] enabled
[ 0.000000] efi: UEFI not found.
[ 0.000000] Zone ranges:
[ 0.000000] DMA32 [mem 0x0000000080200000-0x0000000083ffffff]
[ 0.000000] Normal empty
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000080200000-0x0000000083ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000080200000-0x0000000083ffffff]
[ 0.000000] SBI specification v0.2 detected
[ 0.000000] SBI implementation ID=0x1 Version=0x9
[ 0.000000] SBI TIME extension detected
[ 0.000000] SBI IPI extension detected
[ 0.000000] SBI RFENCE extension detected
[ 0.000000] SBI v0.2 HSM extension detected
[ 0.000000] riscv: ISA extensions acdfhimsu
[ 0.000000] riscv: ELF capabilities acdfim
[ 0.000000] percpu: Embedded 17 pages/cpu s30696 r8192 d30744 u69632
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 15655
[ 0.000000] Kernel command line: rootwait root=/dev/vda ro console=ttyS0 earlycon=sbi
[ 0.000000] Dentry cache hash table entries: 8192 (order: 4, 65536 bytes, linear)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 3, 32768 bytes, linear)
[ 0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] fixmap : 0xffffffcefee00000 - 0xffffffceff000000 (2048 kB)
[ 0.000000] pci io : 0xffffffceff000000 - 0xffffffcf00000000 ( 16 MB)
[ 0.000000] vmemmap : 0xffffffcf00000000 - 0xffffffcfffffffff (4095 MB)
[ 0.000000] vmalloc : 0xffffffd000000000 - 0xffffffdfffffffff (65535 MB)
[ 0.000000] lowmem : 0xffffffe000000000 - 0xffffffe003e00000 ( 62 MB)
[ 0.000000] kernel : 0xffffffff80000000 - 0xffffffffffffffff (2047 MB)
[ 0.000000] Memory: 52788K/63488K available (6184K kernel code, 888K rwdata, 1917K rodata, 294K init, 297K bss, 10700K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] rcu: Hierarchical RCU implementation.
[ 0.000000] rcu: RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1.
[ 0.000000] rcu: RCU debug extended QS entry/exit.
[ 0.000000] Tracing variant of Tasks RCU enabled.
[ 0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[ 0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[ 0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[ 0.000000] riscv-intc: 64 local interrupts mapped
[ 0.000000] plic: plic@c000000: mapped 53 interrupts with 1 handlers for 2 contexts.
...
Welcome to Buildroot
buildroot login: root
# cat /proc/cpuinfo
processor : 0
hart : 0
isa : rv64imafdcsuh
mmu : sv48

# file /bin/busybox
/bin/busybox: setuid ELF 32-bit LSB shared object, UCB RISC-V, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-riscv32-ilp32d.so.1, for GNU/Linux 5.15.0, stripped
# ca[ 78.386630] random: fast init done
# cat /proc/meminfo
MemTotal: 53076 kB
MemFree: 40264 kB
MemAvailable: 40244 kB
Buffers: 236 kB
Cached: 1560 kB
SwapCached: 0 kB
Active: 1700 kB
Inactive: 516 kB
Active(anon): 40 kB
Inactive(anon): 424 kB
Active(file): 1660 kB
Inactive(file): 92 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 444 kB
Mapped: 1188 kB
Shmem: 44 kB
KReclaimable: 952 kB
Slab: 5744 kB
SReclaimable: 952 kB
SUnreclaim: 4792 kB
KernelStack: 624 kB
PageTables: 156 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 26536 kB
Committed_AS: 1748 kB
VmallocTotal: 67108863 kB
VmallocUsed: 652 kB
VmallocChunk: 0 kB
Percpu: 80 kB
#

- Run rv32 with rv32 rootfs:
$ ./build/qemu-system-riscv32 -cpu rv32,x-h=true -M virt -m 64m -nographic -bios qemu_riscv32_virt_defconfig/images/fw_jump.bin -kernel build-rv32/Image -drive file qemu_riscv32_virt_defconfig/images/rootfs.ext2,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 -append "rootwait root=/dev/vda ro console=ttyS0 earlycon=sbi" -netdev user,id=net0 -device virtio-net-device,netdev=net0

QEMU emulator version 6.2.50 (v6.2.0-29-g196d7182c8)
OpenSBI v0.9
[ 0.000000] Linux version 5.16.0-rc6-00017-g750f87086bdd-dirty (guoren@guoren-Z87-HD3) (riscv32-buildroot-linux-gnu-gcc.br_real (Buildroot 2021.11-201-g7600ca7960-dirty) 10.3.0, GNU ld (GNU Binutils) 2.36.1) #7 SMP Tue Dec 28 21:02:21 CST 2021
[ 0.000000] OF: fdt: Ignoring memory range 0x80000000 - 0x80400000
[ 0.000000] Machine model: riscv-virtio,qemu
[ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[ 0.000000] printk: bootconsole [sbi0] enabled
[ 0.000000] efi: UEFI not found.
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000080400000-0x0000000083ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000080400000-0x0000000083ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000080400000-0x0000000083ffffff]
[ 0.000000] SBI specification v0.2 detected
[ 0.000000] SBI implementation ID=0x1 Version=0x9
[ 0.000000] SBI TIME extension detected
[ 0.000000] SBI IPI extension detected
[ 0.000000] SBI RFENCE extension detected
[ 0.000000] SBI v0.2 HSM extension detected
[ 0.000000] riscv: ISA extensions acdfhimsu
[ 0.000000] riscv: ELF capabilities acdfim
[ 0.000000] percpu: Embedded 12 pages/cpu s16600 r8192 d24360 u49152
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 15240
[ 0.000000] Kernel command line: rootwait root=/dev/vda ro console=ttyS0 earlycon=sbi
[ 0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes, linear)
[ 0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] fixmap : 0x9dc00000 - 0x9e000000 (4096 kB)
[ 0.000000] pci io : 0x9e000000 - 0x9f000000 ( 16 MB)
[ 0.000000] vmemmap : 0x9f000000 - 0x9fffffff ( 15 MB)
[ 0.000000] vmalloc : 0xa0000000 - 0xbfffffff ( 511 MB)
[ 0.000000] lowmem : 0xc0000000 - 0xc3c00000 ( 60 MB)
[ 0.000000] Memory: 51924K/61440K available (6117K kernel code, 695K rwdata, 1594K rodata, 255K init, 241K bss, 9516K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] rcu: Hierarchical RCU implementation.
[ 0.000000] rcu: RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1.
[ 0.000000] rcu: RCU debug extended QS entry/exit.
[ 0.000000] Tracing variant of Tasks RCU enabled.
[ 0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[ 0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[ 0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[ 0.000000] riscv-intc: 32 local interrupts mapped
[ 0.000000] plic: plic@c000000: mapped 53 interrupts with 1 handlers for 2 contexts.
...
Welcome to Buildroot
buildroot login: root
# cat /proc/cpuinfo
processor : 0
hart : 0
isa : rv32imafdcsuh
mmu : sv32

# file /bin/busybox
/bin/busybox: setuid ELF 32-bit LSB shared object, UCB RISC-V, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-riscv32-ilp32d.so.1, for GNU/Linux 5.15.0, stripped
[ 79.320589] random: fast init done
# cat /proc/meminfo
MemTotal: 52176 kB
MemFree: 41012 kB
MemAvailable: 42176 kB
Buffers: 644 kB
Cached: 2724 kB
SwapCached: 0 kB
Active: 3128 kB
Inactive: 752 kB
Active(anon): 40 kB
Inactive(anon): 516 kB
Active(file): 3088 kB
Inactive(file): 236 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 4 kB
Writeback: 0 kB
AnonPages: 556 kB
Mapped: 2172 kB
Shmem: 44 kB
KReclaimable: 656 kB
Slab: 3684 kB
SReclaimable: 656 kB
SUnreclaim: 3028 kB
KernelStack: 312 kB
PageTables: 88 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 26088 kB
Committed_AS: 2088 kB
VmallocTotal: 524287 kB
VmallocUsed: 12 kB
VmallocChunk: 0 kB
Percpu: 60 kB
#

Some conclusions:
- kernel statics:
64: Memory: 52788K/63488K available (6184K kernel code, 888K rwdata, 1917K rodata, 294K init, 297K bss, 10700K reserved)
32: Memory: 51924K/61440K available (6117K kernel code, 695K rwdata, 1594K rodata, 255K init, 241K bss, 9516K reserved)
rv32 better than rv64: 1% 22% 17% 13% 19% 11%
The code size is very similar, but data size rv32 would be better.

- rv32 kernel runtime KernelStack, Slab... are smaller,
rv64: MemTotal: 53076 kB, MemFree: 40264 kB
rv32: MemTotal: 52176 + 2048 kB, MemFree: 41012 + 2048 kB
rv32 better than rv64: 2% 6%

(Because opensbi problem, we could add another 2MB for rv32.)
Overall, rv64-compat is 6% worse than rv32-full at memory footprint.
If the user space memory usage increases, the gap will be further
reduced.

- Qemu, kernel, rv32 = rv64 defconfig, rootfs, opensbi
are the same in this comparison.

Changes in v2:
- Add __ARCH_WANT_COMPAT_STAT suggested
- Cleanup fcntl compatduplicate definitions
- Cleanup compat.h
- Move rv32_defconfig into Makefile
- Fixup rv64 rootfs boot failed, remove hw_compat_mode_detect
- Move SYSVIPC_COMPAT into init/Kconfig
- Simplify compat_elf_check

Guo Ren (17):
kconfig: Add SYSVIPC_COMPAT for all architectures
fs: stat: compat: Add __ARCH_WANT_COMPAT_STAT
asm-generic: fcntl: compat: Remove duplicate definitions
asm-generic: compat: Cleanup duplicate definitions
syscalls: compat: Fix the missing part for __SYSCALL_COMPAT
riscv: Fixup difference with defconfig
riscv: compat: Add basic compat date type implementation
riscv: compat: Re-implement TASK_SIZE for COMPAT_32BIT
riscv: compat: syscall: Add compat_sys_call_table implementation
riscv: compat: syscall: Add entry.S implementation
riscv: compat: Add elf.h implementation
riscv: compat: vdso: Add rv32 VDSO base code implementation
riscv: compat: vdso: Add setup additional pages implementation
riscv: compat: signal: Add rt_frame implementation
riscv: compat: ptrace: Add compat_arch_ptrace implement
riscv: compat: Add UXL_32 support in start_thread
riscv: compat: Add COMPAT Kbuild skeletal support

arch/arm64/Kconfig | 4 -
arch/arm64/include/asm/compat.h | 112 +-------
arch/arm64/include/asm/unistd.h | 1 +
arch/mips/Kconfig | 5 -
arch/mips/include/asm/compat.h | 24 +-
arch/mips/include/asm/unistd.h | 2 +
arch/parisc/Kconfig | 4 -
arch/parisc/include/asm/compat.h | 47 +---
arch/parisc/include/asm/unistd.h | 1 +
arch/powerpc/Kconfig | 5 -
arch/powerpc/include/asm/compat.h | 51 +---
arch/powerpc/include/asm/unistd.h | 1 +
arch/riscv/Kconfig | 19 ++
arch/riscv/Makefile | 9 +
arch/riscv/configs/rv32_defconfig | 135 ----------
arch/riscv/include/asm/compat.h | 132 ++++++++++
arch/riscv/include/asm/csr.h | 7 +
arch/riscv/include/asm/elf.h | 54 +++-
arch/riscv/include/asm/mmu.h | 1 +
arch/riscv/include/asm/pgtable.h | 11 +-
arch/riscv/include/asm/processor.h | 6 +
arch/riscv/include/asm/syscall.h | 3 +
arch/riscv/include/asm/thread_info.h | 1 +
arch/riscv/include/asm/vdso.h | 9 +
arch/riscv/include/uapi/asm/unistd.h | 2 +-
arch/riscv/kernel/Makefile | 3 +
arch/riscv/kernel/compat_signal.c | 243 ++++++++++++++++++
arch/riscv/kernel/compat_syscall_table.c | 72 ++++++
arch/riscv/kernel/compat_vdso/.gitignore | 2 +
arch/riscv/kernel/compat_vdso/Makefile | 68 +++++
arch/riscv/kernel/compat_vdso/compat_vdso.S | 8 +
.../kernel/compat_vdso/compat_vdso.lds.S | 3 +
arch/riscv/kernel/compat_vdso/flush_icache.S | 3 +
.../compat_vdso/gen_compat_vdso_offsets.sh | 5 +
arch/riscv/kernel/compat_vdso/getcpu.S | 3 +
arch/riscv/kernel/compat_vdso/note.S | 3 +
arch/riscv/kernel/compat_vdso/rt_sigreturn.S | 3 +
arch/riscv/kernel/entry.S | 18 +-
arch/riscv/kernel/process.c | 5 +
arch/riscv/kernel/ptrace.c | 87 ++++++-
arch/riscv/kernel/signal.c | 13 +-
arch/riscv/kernel/sys_riscv.c | 6 +-
arch/riscv/kernel/vdso.c | 104 +++++---
arch/riscv/kernel/vdso/vdso.S | 6 +-
arch/s390/Kconfig | 3 -
arch/s390/include/asm/compat.h | 113 +-------
arch/s390/include/asm/unistd.h | 1 +
arch/sparc/Kconfig | 5 -
arch/sparc/include/asm/compat.h | 43 ++--
arch/sparc/include/asm/unistd.h | 1 +
arch/x86/Kconfig | 4 -
arch/x86/include/asm/compat.h | 118 +--------
arch/x86/include/asm/unistd.h | 1 +
drivers/firmware/efi/libstub/efi-stub.c | 2 +-
fs/stat.c | 2 +-
include/asm-generic/compat.h | 122 +++++++++
include/uapi/asm-generic/fcntl.h | 2 +-
include/uapi/asm-generic/unistd.h | 4 +-
init/Kconfig | 4 +
tools/include/uapi/asm-generic/unistd.h | 4 +-
60 files changed, 1076 insertions(+), 654 deletions(-)
delete mode 100644 arch/riscv/configs/rv32_defconfig
create mode 100644 arch/riscv/include/asm/compat.h
create mode 100644 arch/riscv/kernel/compat_signal.c
create mode 100644 arch/riscv/kernel/compat_syscall_table.c
create mode 100644 arch/riscv/kernel/compat_vdso/.gitignore
create mode 100644 arch/riscv/kernel/compat_vdso/Makefile
create mode 100644 arch/riscv/kernel/compat_vdso/compat_vdso.S
create mode 100644 arch/riscv/kernel/compat_vdso/compat_vdso.lds.S
create mode 100644 arch/riscv/kernel/compat_vdso/flush_icache.S
create mode 100755 arch/riscv/kernel/compat_vdso/gen_compat_vdso_offsets.sh
create mode 100644 arch/riscv/kernel/compat_vdso/getcpu.S
create mode 100644 arch/riscv/kernel/compat_vdso/note.S
create mode 100644 arch/riscv/kernel/compat_vdso/rt_sigreturn.S

--
2.25.1

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