The pre_init stub consists of two syscalls mouting the host's FS via 9pfs and then calling the actual init binary, which can now use normal dynamic linking. Based on the x86 code provide an ARM and ARM64 implementation of that. Beside removing the need for static linkage it reduces the size of the kvmtool binary by quite a lot (numbers for aarch64): -rwxr-xr-x 1 root root 9952 Nov 16 14:37 guest/init -rwxr-xr-x 1 root root 512 Nov 16 14:37 guest/pre_init -rwxr-xr-x 2 root root 1284704 Nov 16 14:37 lkvm vs. the old version: -rwxr-xr-x 1 root root 776024 Nov 16 14:38 guest/init -rwxr-xr-x 2 root root 2050112 Nov 16 14:38 lkvm Tested on Midway and Juno. Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> --- Makefile | 2 ++ arm/aarch32/init.S | 44 ++++++++++++++++++++++++++++++++++++++++++++ arm/aarch64/init.S | 44 ++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 90 insertions(+) create mode 100644 arm/aarch32/init.S create mode 100644 arm/aarch64/init.S diff --git a/Makefile b/Makefile index 54bdd31..57b0bdd 100644 --- a/Makefile +++ b/Makefile @@ -161,6 +161,7 @@ ifeq ($(ARCH), arm) OBJS += $(OBJS_ARM_COMMON) OBJS += arm/aarch32/arm-cpu.o OBJS += arm/aarch32/kvm-cpu.o + ARCH_PRE_INIT = arm/aarch32/init.S ARCH_INCLUDE := $(HDRS_ARM_COMMON) ARCH_INCLUDE += -Iarm/aarch32/include CFLAGS += -march=armv7-a @@ -174,6 +175,7 @@ ifeq ($(ARCH), arm64) OBJS += $(OBJS_ARM_COMMON) OBJS += arm/aarch64/arm-cpu.o OBJS += arm/aarch64/kvm-cpu.o + ARCH_PRE_INIT = arm/aarch64/init.S ARCH_INCLUDE := $(HDRS_ARM_COMMON) ARCH_INCLUDE += -Iarm/aarch64/include diff --git a/arm/aarch32/init.S b/arm/aarch32/init.S new file mode 100644 index 0000000..c023195 --- /dev/null +++ b/arm/aarch32/init.S @@ -0,0 +1,44 @@ +/* + * #!/bin/sh + * mount -t 9p -o trans=virtio,version=9p2000.L hostfs /host + * /virt/init $* + */ + +#include <asm/unistd.h> + +.text +.globl _start +_start: + + mov r7, #__NR_mount + ldr r0, =.m_dev + ldr r1, =.m_dir + ldr r2, =.m_typ + mov r3, #1 // MS_RDONLY + ldr r4, =.m_opt + svc #0 + + mov r7, #__NR_execve + ldr r0, =.e_nam // 1st arg: filename + add r1, sp, #4 // 2nd arg: argv[0] + str r0, [r1] // change argv[0] + ldr r2, [sp] + add r2, r2, #1 // r2 = argc + 1 + add r2, r1, r2, lsl #2 // 3rd arg: envp = argv[0] + argc + 1 + svc #0 + + mov r7, #__NR_exit + mov r0, #1 + svc #0 // panic + +.m_dev: +.string "hostfs" +.m_dir: +.string "/host" +.m_typ: +.string "9p" +.m_opt: +.string "trans=virtio,version=9p2000.L" + +.e_nam: +.string "/virt/init" diff --git a/arm/aarch64/init.S b/arm/aarch64/init.S new file mode 100644 index 0000000..567bf97 --- /dev/null +++ b/arm/aarch64/init.S @@ -0,0 +1,44 @@ +/* + * #!/bin/sh + * mount -t 9p -o trans=virtio,version=9p2000.L hostfs /host + * /virt/init $* + */ + +#include <asm/unistd.h> + +.text +.globl _start +_start: + + mov x8, #__NR_mount + ldr x0, =.m_dev + ldr x1, =.m_dir + ldr x2, =.m_typ + mov x3, #1 // MS_RDONLY + ldr x4, =.m_opt + svc #0 + + mov x8, #__NR_execve + ldr x0, =.e_nam // 1st arg: filename + add x1, sp, #8 // 2nd arg: argv (passed through) + str x0, [x1] // change argv[0] to contain filename + ldr x2, [sp] + add x2, x2, #1 // x2 = argc + 1 + add x2, x1, x2, lsl #3 // 3rd arg: envp = argv[0] + argc + 1 + svc #0 + + mov x8, #__NR_exit + mov x0, #1 + svc #0 // panic + +.m_dev: +.string "hostfs" +.m_dir: +.string "/host" +.m_typ: +.string "9p" +.m_opt: +.string "trans=virtio,version=9p2000.L" + +.e_nam: +.string "/virt/init" -- 2.6.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
