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s390/boot: workaround llvm IAS bug 

For at least the mvc and clc instructions llvm's integrated assembler can
generate incorrect code. In particular this happens with decompressor boot
code. The reason seems to be that relocations for the second displacement
of each instruction are at incorrect locations (-/+: gas vs llvm IAS):

mvc     __LC_IO_NEW_PSW(16),.Lnewpsw

results in

        4:      d2 0f 01 f0 00 00       mvc     496(16,%r0),0
-                       8: R_390_12     .head.text+0x10
+		       6: R_390_12     .head.text+0x10

and
clc     0(3,%r4),.L_hdr
results in

      258:      d5 02 40 00 00 00       clc     0(3,%r4),0
-                       25c: R_390_12   .head.text+0x324
+		       25a: R_390_12   .head.text+0x324

Workaround this by writing the code in a different way.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://github.com/llvm/llvm-project/issues/55411
Link: https://lore.kernel.org/r/20220511120532.2228616-7-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2022-05-11 14:05:30 +02:00
parent adda746629
commit e9953b729b
1 changed files with 21 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
arch/s390/boot/head.S
View File

@ -42,7 +42,8 @@ ipl_start:
# subroutine to wait for end I/O
#
.Lirqwait:
mvc __LC_IO_NEW_PSW(16),.Lnewpsw # set up IO interrupt psw
larl %r13,.Lnewpsw # set up IO interrupt psw
mvc __LC_IO_NEW_PSW(16),0(%r13)
lpsw .Lwaitpsw
.Lioint:
br %r14
@ -155,9 +156,11 @@ ipl_start:
lr %r2,%r3
.Lnotrunc:
l %r4,.Linitrd
clc 0(3,%r4),.L_hdr # if it is HDRx
larl %r13,.L_hdr
clc 0(3,%r4),0(%r13) # if it is HDRx
bz .Lagain1 # skip dataset header
clc 0(3,%r4),.L_eof # if it is EOFx
larl %r13,.L_eof
clc 0(3,%r4),0(%r13) # if it is EOFx
bz .Lagain1 # skip dateset trailer
lr %r5,%r2
@ -181,9 +184,11 @@ ipl_start:
.Lrdcont:
l %r2,.Linitrd
clc 0(3,%r2),.L_hdr # skip HDRx and EOFx
larl %r13,.L_hdr # skip HDRx and EOFx
clc 0(3,%r2),0(%r13)
bz .Lagain2
clc 0(3,%r2),.L_eof
larl %r13,.L_eof
clc 0(3,%r2),0(%r13)
bz .Lagain2
#
@ -260,20 +265,23 @@ SYM_CODE_START_LOCAL(startup_normal)
.fill 16,4,0x0
0: lmh %r0,%r15,0(%r13) # clear high-order half of gprs
sam64 # switch to 64 bit addressing mode
basr %r13,0 # get base
.LPG0:
mvc __LC_EXT_NEW_PSW(16),.Lext_new_psw-.LPG0(%r13)
mvc __LC_PGM_NEW_PSW(16),.Lpgm_new_psw-.LPG0(%r13)
mvc __LC_IO_NEW_PSW(16),.Lio_new_psw-.LPG0(%r13)
larl %r13,.Lext_new_psw
mvc __LC_EXT_NEW_PSW(16),0(%r13)
larl %r13,.Lpgm_new_psw
mvc __LC_PGM_NEW_PSW(16),0(%r13)
larl %r13,.Lio_new_psw
mvc __LC_IO_NEW_PSW(16),0(%r13)
xc 0x200(256),0x200 # partially clear lowcore
xc 0x300(256),0x300
xc 0xe00(256),0xe00
xc 0xf00(256),0xf00
lctlg %c0,%c15,.Lctl-.LPG0(%r13) # load control registers
larl %r13,.Lctl
lctlg %c0,%c15,0(%r13) # load control registers
stcke __LC_BOOT_CLOCK
mvc __LC_LAST_UPDATE_CLOCK(8),__LC_BOOT_CLOCK+1
spt 6f-.LPG0(%r13)
mvc __LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
larl %r13,6f
spt 0(%r13)
mvc __LC_LAST_UPDATE_TIMER(8),0(%r13)
larl %r15,_stack_end-STACK_FRAME_OVERHEAD
brasl %r14,sclp_early_setup_buffer
brasl %r14,verify_facilities