michael/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

powerpc/32: Restore clearing of MSR[RI] at interrupt/syscall exit

Browse Source 
Commit 13799748b9 ("powerpc/64: use interrupt restart table to speed
up return from interrupt") removed the inconditional clearing of
MSR[RI] when returning from interrupt into kernel. But powerpc/32
doesn't implement interrupt restart table hence still need MSR[RI]
to be cleared.

It could be added back in interrupt_exit_kernel_prepare() but it is
easier and better to add it back in entry_32.S for following reasons:
- Writing to MSR must be followed by a synchronising instruction
- The smaller the non recoverable section is the better it is

So add a macro called clr_ri and use it in the three places that play
up with SRR0/SRR1. Use it just before another mtspr for synchronisation
to avoid having to add an isync.

Now that's done in entry_32.S, exit_must_hard_disable() can return
false for non book3s/64, taking into account that BOOKE doesn't have
MSR_RI.

Also add back blacklisting syscall_exit_finish for kprobe. This was
initially added by commit 7cdf440138 ("powerpc/entry32: Blacklist
syscall exit points for kprobe.") then lost with
commit 6f76a01173 ("powerpc/syscall: implement system call
entry/exit logic in C for PPC32").

Fixes: 6f76a01173 ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
Fixes: 13799748b9 ("powerpc/64: use interrupt restart table to speed up return from interrupt")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/66d0ab070563ad460ed481328ab0887c27f21a2c.1757593807.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy
2025-09-11 14:30:12 +02:00
committed by Madhavan Srinivasan
parent 98fa236044
commit 2997876c4a
2 changed files with 18 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
arch/powerpc/kernel/entry_32.S
View File

@@ -101,6 +101,17 @@ SYM_FUNC_END(__kuep_unlock)
.endm
#endif
.macro clr_ri trash
#ifndef CONFIG_BOOKE
#ifdef CONFIG_PPC_8xx
mtspr SPRN_NRI, \trash
#else
li \trash, MSR_KERNEL & ~MSR_RI
mtmsr \trash
#endif
#endif
.endm
.globl transfer_to_syscall
transfer_to_syscall:
stw r3, ORIG_GPR3(r1)
@@ -149,6 +160,7 @@ ret_from_syscall:
cmpwi r3,0
REST_GPR(3, r1)
syscall_exit_finish:
clr_ri r4
mtspr SPRN_SRR0,r7
mtspr SPRN_SRR1,r8
@@ -168,6 +180,7 @@ syscall_exit_finish:
REST_GPR(0, r1)
REST_GPRS(3, 12, r1)
b 1b
_ASM_NOKPROBE_SYMBOL(syscall_exit_finish)
#ifdef CONFIG_44x
.L44x_icache_flush:
@@ -224,10 +237,11 @@ fast_exception_return:
/* Clear the exception marker on the stack to avoid confusing stacktrace */
li r10, 0
stw r10, 8(r11)
REST_GPR(10, r11)
clr_ri r10
mtspr SPRN_SRR1,r9
mtspr SPRN_SRR0,r12
REST_GPR(9, r11)
REST_GPR(10, r11)
REST_GPR(12, r11)
REST_GPR(11, r11)
rfi
@@ -256,6 +270,7 @@ interrupt_return:
.Lfast_user_interrupt_return:
lwz r11,_NIP(r1)
lwz r12,_MSR(r1)
clr_ri r4
mtspr SPRN_SRR0,r11
mtspr SPRN_SRR1,r12
@@ -299,6 +314,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
cmpwi cr1,r3,0
lwz r11,_NIP(r1)
lwz r12,_MSR(r1)
clr_ri r4
mtspr SPRN_SRR0,r11
mtspr SPRN_SRR1,r12

2
arch/powerpc/kernel/interrupt.c
View File

@@ -38,7 +38,7 @@ static inline bool exit_must_hard_disable(void)
#else
static inline bool exit_must_hard_disable(void)
{
return true;
return false;
}
#endif