6.12-stable review patch. If anyone has any objections, please let me know.
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From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit 861efb8a48ee8b73ae4e8817509cd4e82fd52bc4 ]
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 c974809a26a1 ("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: 683430200315 ("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... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kexec/relocate_32.S | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kexec/relocate_32.S b/arch/powerpc/kexec/relocate_32.S index 104c9911f4061..dd86e338307d3 100644 --- a/arch/powerpc/kexec/relocate_32.S +++ b/arch/powerpc/kexec/relocate_32.S @@ -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 */