| Message ID | cf0a050d124d4f426cdc7a74009d17b01d8d8969.1620465917.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/uaccess: Fix __get_user() with CONFIG_CC_HAS_ASM_GOTO_OUTPUT | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (7619d98e5041d5c25aba5428704dba6121237a9a) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
On Sat, 8 May 2021 09:25:32 +0000 (UTC), Christophe Leroy wrote: > 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: > > [...] Applied to powerpc/fixes. [1/1] powerpc/uaccess: Fix __get_user() with CONFIG_CC_HAS_ASM_GOTO_OUTPUT https://git.kernel.org/powerpc/c/7315e457d6bc342d06ba0b7ee498221c5237a547 cheers
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)
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> --- arch/powerpc/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)