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powerpc/kexec: fix physical address calculation in clear_utlb_entry()

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In relocate_32.S, function clear_utlb_entry() goes into real mode. To
do so, it has to calculate the physical address based on the virtual
address. To get the virtual address it uses 'bl' which is problematic
(see commit c974809a26 ("powerpc/vdso: Avoid link stack corruption
in __get_datapage()")). In addition, the calculation is done on a
wrong address because 'bl' loads LR with the address of the following
instruction, not the address of the target. So when the target is not
the instruction following the 'bl' instruction, it may lead to
unexpected behaviour.

Fix it by re-writing the code so that is goes via another path which
is based 'bcl 20,31,.+4' which is the right instruction to use for that.

Fixes: 6834302003 ("powerpc/47x: Kernel support for KEXEC")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/dc4f9616fba9c05c5dbf9b4b5480eb1c362adc17.1741256651.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy
2025-03-06 11:24:28 +01:00
committed by Madhavan Srinivasan
parent 1e4d73d06c
commit 861efb8a48
1 changed files with 2 additions and 5 deletions
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7
arch/powerpc/kexec/relocate_32.S
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@@ -348,16 +348,13 @@ write_utlb:
rlwinm r10, r24, 0, 22, 27
cmpwi r10, PPC47x_TLB0_4K
bne 0f
li r10, 0x1000 /* r10 = 4k */
ANNOTATE_INTRA_FUNCTION_CALL
bl 1f
beq 0f
0:
/* Defaults to 256M */
lis r10, 0x1000
bcl 20,31,$+4
0: bcl 20,31,$+4
1: mflr r4
addi r4, r4, (2f-1b) /* virtual address of 2f */