From: Ilya Leoshkevich Date: Wed, 25 Jun 2025 15:36:51 +0000 (+0200) Subject: s390/boot: Introduce jump_to_kernel() function X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=996f7f292b7e190138738bd9213616a544837a41;p=thirdparty%2Fkernel%2Fstable.git s390/boot: Introduce jump_to_kernel() function Introduce a global function that jumps from the decompressor to the decompressed kernel. Put its address into svc_old_psw, from where GDB can take it without loading decompressor symbols. It should be available throughout the entire decompressor execution, because it's placed there statically, and nothing in the decompressor uses the SVC instruction. Acked-by: Heiko Carstens Signed-off-by: Ilya Leoshkevich Tested-by: Alexander Gordeev Link: https://lore.kernel.org/r/20250625154220.75300-2-iii@linux.ibm.com Signed-off-by: Alexander Gordeev --- diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile index 0986c7c67eaf..02f2cf082748 100644 --- a/arch/s390/boot/Makefile +++ b/arch/s390/boot/Makefile @@ -27,7 +27,7 @@ CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char obj-y := head.o als.o startup.o physmem_info.o ipl_parm.o ipl_report.o vmem.o obj-y += string.o ebcdic.o sclp_early_core.o mem.o ipl_vmparm.o cmdline.o obj-y += version.o pgm_check.o ctype.o ipl_data.o relocs.o alternative.o -obj-y += uv.o printk.o +obj-y += uv.o printk.o trampoline.o obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o obj-y += $(if $(CONFIG_KERNEL_UNCOMPRESSED),,decompressor.o) info.o obj-$(CONFIG_KERNEL_ZSTD) += clz_ctz.o diff --git a/arch/s390/boot/boot.h b/arch/s390/boot/boot.h index 759aaf5b4fd2..c0152db285f0 100644 --- a/arch/s390/boot/boot.h +++ b/arch/s390/boot/boot.h @@ -74,6 +74,7 @@ void print_stacktrace(unsigned long sp); void error(char *m); int get_random(unsigned long limit, unsigned long *value); void boot_rb_dump(void); +void __noreturn jump_to_kernel(psw_t *psw); #ifndef boot_fmt #define boot_fmt(fmt) fmt diff --git a/arch/s390/boot/ipl_data.c b/arch/s390/boot/ipl_data.c index 0846e2b249c6..c4130a80b058 100644 --- a/arch/s390/boot/ipl_data.c +++ b/arch/s390/boot/ipl_data.c @@ -16,7 +16,9 @@ struct ipl_lowcore { struct ccw0 ccwpgm[2]; /* 0x0008 */ u8 fill[56]; /* 0x0018 */ struct ccw0 ccwpgmcc[20]; /* 0x0050 */ - u8 pad_0xf0[0x01a0-0x00f0]; /* 0x00f0 */ + u8 pad_0xf0[0x0140-0x00f0]; /* 0x00f0 */ + psw_t svc_old_psw; /* 0x0140 */ + u8 pad_0x150[0x01a0-0x0150]; /* 0x0150 */ psw_t restart_psw; /* 0x01a0 */ psw_t external_new_psw; /* 0x01b0 */ psw_t svc_new_psw; /* 0x01c0 */ @@ -75,6 +77,11 @@ static struct ipl_lowcore ipl_lowcore __used __section(".ipldata") = { [18] = CCW0(CCW_CMD_READ_IPL, 0x690, 0x50, CCW_FLAG_SLI | CCW_FLAG_CC), [19] = CCW0(CCW_CMD_READ_IPL, 0x6e0, 0x50, CCW_FLAG_SLI), }, + /* + * Let the GDB's lx-symbols command find the jump_to_kernel symbol + * without having to load decompressor symbols. + */ + .svc_old_psw = { .mask = 0, .addr = (unsigned long)jump_to_kernel }, .restart_psw = { .mask = 0, .addr = IPL_START, }, .external_new_psw = { .mask = PSW_MASK_DISABLED, .addr = __LC_EXT_NEW_PSW, }, .svc_new_psw = { .mask = PSW_MASK_DISABLED, .addr = __LC_SVC_NEW_PSW, }, diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index da8337e63a3e..305e6c791071 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -642,5 +642,5 @@ void startup_kernel(void) psw.addr = __kaslr_offset + vmlinux.entry; psw.mask = PSW_KERNEL_BITS; boot_debug("Starting kernel at: 0x%016lx\n", psw.addr); - __load_psw(psw); + jump_to_kernel(&psw); } diff --git a/arch/s390/boot/trampoline.S b/arch/s390/boot/trampoline.S new file mode 100644 index 000000000000..1cb5adf005ea --- /dev/null +++ b/arch/s390/boot/trampoline.S @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include + +# This function is identical to __load_psw(), but the lx-symbols GDB command +# puts a breakpoint on it, so it needs to be kept separate. +SYM_CODE_START(jump_to_kernel) + lpswe 0(%r2) +SYM_CODE_END(jump_to_kernel)