The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f3b7e73b2c6619884351a3a0a7468642f852b8a2 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich iii@linux.ibm.com Date: Wed, 19 Jan 2022 19:26:37 +0100 Subject: [PATCH] s390/module: fix loading modules with a lot of relocations
If the size of the PLT entries generated by apply_rela() exceeds 64KiB, the first ones can no longer reach __jump_r1 with brc. Fix by using brcl. An alternative solution is to add a __jump_r1 copy after every 64KiB, however, the space savings are quite small and do not justify the additional complexity.
Fixes: f19fbd5ed642 ("s390: introduce execute-trampolines for branches") Cc: stable@vger.kernel.org Reported-by: Andrea Righi andrea.righi@canonical.com Signed-off-by: Ilya Leoshkevich iii@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Cc: Vasily Gorbik gor@linux.ibm.com Cc: Christian Borntraeger borntraeger@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c index d52d85367bf7..b032e556eeb7 100644 --- a/arch/s390/kernel/module.c +++ b/arch/s390/kernel/module.c @@ -33,7 +33,7 @@ #define DEBUGP(fmt , ...) #endif
-#define PLT_ENTRY_SIZE 20 +#define PLT_ENTRY_SIZE 22
void *module_alloc(unsigned long size) { @@ -341,27 +341,26 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */ case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */ if (info->plt_initialized == 0) { - unsigned int insn[5]; - unsigned int *ip = me->core_layout.base + - me->arch.plt_offset + - info->plt_offset; - - insn[0] = 0x0d10e310; /* basr 1,0 */ - insn[1] = 0x100a0004; /* lg 1,10(1) */ + unsigned char insn[PLT_ENTRY_SIZE]; + char *plt_base; + char *ip; + + plt_base = me->core_layout.base + me->arch.plt_offset; + ip = plt_base + info->plt_offset; + *(int *)insn = 0x0d10e310; /* basr 1,0 */ + *(int *)&insn[4] = 0x100c0004; /* lg 1,12(1) */ if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) { - unsigned int *ij; - ij = me->core_layout.base + - me->arch.plt_offset + - me->arch.plt_size - PLT_ENTRY_SIZE; - insn[2] = 0xa7f40000 + /* j __jump_r1 */ - (unsigned int)(u16) - (((unsigned long) ij - 8 - - (unsigned long) ip) / 2); + char *jump_r1; + + jump_r1 = plt_base + me->arch.plt_size - + PLT_ENTRY_SIZE; + /* brcl 0xf,__jump_r1 */ + *(short *)&insn[8] = 0xc0f4; + *(int *)&insn[10] = (jump_r1 - (ip + 8)) / 2; } else { - insn[2] = 0x07f10000; /* br %r1 */ + *(int *)&insn[8] = 0x07f10000; /* br %r1 */ } - insn[3] = (unsigned int) (val >> 32); - insn[4] = (unsigned int) val; + *(long *)&insn[14] = val;
write(ip, insn, sizeof(insn)); info->plt_initialized = 1;