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authorChristophe Leroy <christophe.leroy@csgroup.eu>2021-05-08 09:25:32 +0000
committerMichael Ellerman <mpe@ellerman.id.au>2021-05-12 11:07:39 +1000
commit7315e457d6bc342d06ba0b7ee498221c5237a547 (patch)
treef1b9d1d3f0ccfbd0f03f78e55a14a604053961a6 /arch
parent4f242fc5f2e24412b89e934dad025b10293b2712 (diff)
powerpc/uaccess: Fix __get_user() with CONFIG_CC_HAS_ASM_GOTO_OUTPUT
Building kernel mainline with GCC 11 leads to following failure when starting 'init': init[1]: bad frame in sys_sigreturn: 7ff5a900 nip 001083cc lr 001083c4 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b This is an issue due to a segfault happening in __unsafe_restore_general_regs() in a loop copying registers from user to kernel: 10: 7d 09 03 a6 mtctr r8 14: 80 ca 00 00 lwz r6,0(r10) 18: 80 ea 00 04 lwz r7,4(r10) 1c: 90 c9 00 08 stw r6,8(r9) 20: 90 e9 00 0c stw r7,12(r9) 24: 39 0a 00 08 addi r8,r10,8 28: 39 29 00 08 addi r9,r9,8 2c: 81 4a 00 08 lwz r10,8(r10) <== r10 is clobbered here 30: 81 6a 00 0c lwz r11,12(r10) 34: 91 49 00 08 stw r10,8(r9) 38: 91 69 00 0c stw r11,12(r9) 3c: 39 48 00 08 addi r10,r8,8 40: 39 29 00 08 addi r9,r9,8 44: 42 00 ff d0 bdnz 14 <__unsafe_restore_general_regs+0x14> As shown above, this is due to r10 being re-used by GCC. This didn't happen with CLANG. This is fixed by tagging 'x' output as an earlyclobber operand in __get_user_asm2_goto(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/cf0a050d124d4f426cdc7a74009d17b01d8d8969.1620465917.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/include/asm/uaccess.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index a09e4240c5b1..22c79ab40006 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -157,7 +157,7 @@ do { \
"2: lwz%X1 %L0, %L1\n" \
EX_TABLE(1b, %l2) \
EX_TABLE(2b, %l2) \
- : "=r" (x) \
+ : "=&r" (x) \
: "m" (*addr) \
: \
: label)