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| author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2021-05-08 12:25:32 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-05-12 04:07:39 +0300 |
| commit | 7315e457d6bc342d06ba0b7ee498221c5237a547 (patch) | |
| tree | f1b9d1d3f0ccfbd0f03f78e55a14a604053961a6 | |
| parent | 4f242fc5f2e24412b89e934dad025b10293b2712 (diff) | |
| download | linux-7315e457d6bc342d06ba0b7ee498221c5237a547.tar.xz | |
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
| -rw-r--r-- | arch/powerpc/include/asm/uaccess.h | 2 |
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) |