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powerpc/64s: add a table of implicit soft-masked addresses 

Commit 9d1988ca87 ("powerpc/64: treat low kernel text as irqs
soft-masked") ends up catching too much code, including ret_from_fork,
and parts of interrupt and syscall return that do not expect to be
interrupts to be soft-masked. If an interrupt gets marked pending,
and then the code proceeds out of the implicit soft-masked region it
will fail to deal with the pending interrupt.

Fix this by adding a new table of addresses which explicitly marks
the regions of code that are soft masked. This table is only checked
for interrupts that below __end_soft_masked, so most kernel interrupts
will not have the overhead of the table search.

Fixes: 9d1988ca87 ("powerpc/64: treat low kernel text as irqs soft-masked")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210630074621.2109197-5-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-06-30 17:46:16 +10:00 committed by Michael Ellerman
parent 9b69d48c75
commit 325678fd05
6 changed files with 105 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/powerpc/include/asm/interrupt.h
View File

@ -75,6 +75,7 @@
#ifdef CONFIG_PPC_BOOK3S_64
extern char __end_soft_masked[];
bool search_kernel_soft_mask_table(unsigned long addr);
unsigned long search_kernel_restart_table(unsigned long addr);
DECLARE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
@ -87,7 +88,7 @@ static inline bool is_implicit_soft_masked(struct pt_regs *regs)
if (regs->nip >= (unsigned long)__end_soft_masked)
return false;
return true;
return search_kernel_soft_mask_table(regs->nip);
}
static inline void srr_regs_clobbered(void)

7
arch/powerpc/include/asm/ppc_asm.h
View File

@ -762,6 +762,13 @@ END_FTR_SECTION_NESTED(CPU_FTR_CELL_TB_BUG, CPU_FTR_CELL_TB_BUG, 96)
stringify_in_c(.long (_target) - . ;) \
stringify_in_c(.previous)
#define SOFT_MASK_TABLE(_start, _end) \
stringify_in_c(.section __soft_mask_table,"a";)\
stringify_in_c(.balign 8;) \
stringify_in_c(.llong (_start);) \
stringify_in_c(.llong (_end);) \
stringify_in_c(.previous)
#define RESTART_TABLE(_start, _end, _target) \
stringify_in_c(.section __restart_table,"a";)\
stringify_in_c(.balign 8;) \

62
arch/powerpc/kernel/exceptions-64s.S
View File

@ -428,21 +428,31 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real)
/* If coming from user, skip soft-mask tests. */
andi. r10,r12,MSR_PR
bne 2f
bne 3f
/*
* Kernel code running below __end_soft_masked is implicitly
* soft-masked
* Kernel code running below __end_soft_masked may be
* implicitly soft-masked if it is within the regions
* in the soft mask table.
*/
LOAD_HANDLER(r10, __end_soft_masked)
cmpld r11,r10
bge+ 1f
/* SEARCH_SOFT_MASK_TABLE clobbers r9,r10,r12 */
mtctr r12
stw r9,PACA_EXGEN+EX_CCR(r13)
SEARCH_SOFT_MASK_TABLE
cmpdi r12,0
mfctr r12 /* Restore r12 to SRR1 */
lwz r9,PACA_EXGEN+EX_CCR(r13)
beq 1f /* Not in soft-mask table */
li r10,IMASK
blt- 1f
b 2f /* In soft-mask table, always mask */
/* Test the soft mask state against our interrupt's bit */
lbz r10,PACAIRQSOFTMASK(r13)
1: andi. r10,r10,IMASK
1: lbz r10,PACAIRQSOFTMASK(r13)
2: andi. r10,r10,IMASK
/* Associate vector numbers with bits in paca->irq_happened */
.if IVEC == 0x500 || IVEC == 0xea0
li r10,PACA_IRQ_EE
@ -473,7 +483,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real)
.if ISTACK
andi. r10,r12,MSR_PR /* See if coming from user */
2: mr r10,r1 /* Save r1 */
3: mr r10,r1 /* Save r1 */
subi r1,r1,INT_FRAME_SIZE /* alloc frame on kernel stack */
beq- 100f
ld r1,PACAKSAVE(r13) /* kernel stack to use */
@ -624,6 +634,36 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
303:
.endm
.macro SEARCH_SOFT_MASK_TABLE
#ifdef CONFIG_RELOCATABLE
mr r12,r2
ld r2,PACATOC(r13)
LOAD_REG_ADDR(r9, __start___soft_mask_table)
LOAD_REG_ADDR(r10, __stop___soft_mask_table)
mr r2,r12
#else
LOAD_REG_IMMEDIATE_SYM(r9, r12, __start___soft_mask_table)
LOAD_REG_IMMEDIATE_SYM(r10, r12, __stop___soft_mask_table)
#endif
300:
cmpd r9,r10
beq 302f
ld r12,0(r9)
cmpld r11,r12
blt 301f
ld r12,8(r9)
cmpld r11,r12
bge 301f
li r12,1
b 303f
301:
addi r9,r9,16
b 300b
302:
li r12,0
303:
.endm
/*
* Restore all registers including H/SRR0/1 saved in a stack frame of a
* standard exception.
@ -754,8 +794,8 @@ __start_interrupts:
* scv instructions enter the kernel without changing EE, RI, ME, or HV.
* In particular, this means we can take a maskable interrupt at any point
* in the scv handler, which is unlike any other interrupt. This is solved
* by treating the instruction addresses below __end_soft_masked as being
* soft-masked.
* by treating the instruction addresses in the handler as being soft-masked,
* by adding a SOFT_MASK_TABLE entry for them.
*
* AIL-0 mode scv exceptions go to 0x17000-0x17fff, but we set AIL-3 and
* ensure scv is never executed with relocation off, which means AIL-0
@ -772,6 +812,7 @@ __start_interrupts:
* syscall register convention is in Documentation/powerpc/syscall64-abi.rst
*/
EXC_VIRT_BEGIN(system_call_vectored, 0x3000, 0x1000)
1:
/* SCV 0 */
mr r9,r13
GET_PACA(r13)
@ -801,8 +842,11 @@ EXC_VIRT_BEGIN(system_call_vectored, 0x3000, 0x1000)
b system_call_vectored_sigill
#endif
.endr
2:
EXC_VIRT_END(system_call_vectored, 0x3000, 0x1000)
SOFT_MASK_TABLE(1b, 2b) // Treat scv vectors as soft-masked, see comment above.
#ifdef CONFIG_RELOCATABLE
TRAMP_VIRT_BEGIN(system_call_vectored_tramp)
__LOAD_HANDLER(r10, system_call_vectored_common)

8
arch/powerpc/kernel/interrupt_64.S
View File

@ -207,7 +207,9 @@ syscall_vectored_\name\()_restart:
bl syscall_exit_restart
std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
b .Lsyscall_vectored_\name\()_rst_start
1:
SOFT_MASK_TABLE(.Lsyscall_vectored_\name\()_rst_start, 1b)
RESTART_TABLE(.Lsyscall_vectored_\name\()_rst_start, .Lsyscall_vectored_\name\()_rst_end, syscall_vectored_\name\()_restart)
.endm
@ -410,7 +412,9 @@ syscall_restart:
bl syscall_exit_restart
std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
b .Lsyscall_rst_start
1:
SOFT_MASK_TABLE(.Lsyscall_rst_start, 1b)
RESTART_TABLE(.Lsyscall_rst_start, .Lsyscall_rst_end, syscall_restart)
#endif
@ -607,7 +611,9 @@ interrupt_return_\srr\()_user_restart:
bl interrupt_exit_user_restart
std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
b .Linterrupt_return_\srr\()_user_rst_start
1:
SOFT_MASK_TABLE(.Linterrupt_return_\srr\()_user_rst_start, 1b)
RESTART_TABLE(.Linterrupt_return_\srr\()_user_rst_start, .Linterrupt_return_\srr\()_user_rst_end, interrupt_return_\srr\()_user_restart)
#endif
@ -738,7 +744,9 @@ interrupt_return_\srr\()_kernel_restart:
bl interrupt_exit_kernel_restart
std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
b .Linterrupt_return_\srr\()_kernel_rst_start
1:
SOFT_MASK_TABLE(.Linterrupt_return_\srr\()_kernel_rst_start, 1b)
RESTART_TABLE(.Linterrupt_return_\srr\()_kernel_rst_start, .Linterrupt_return_\srr\()_kernel_rst_end, interrupt_return_\srr\()_kernel_restart)
#endif

9
arch/powerpc/kernel/vmlinux.lds.S
View File

@ -9,6 +9,14 @@
#define EMITS_PT_NOTE
#define RO_EXCEPTION_TABLE_ALIGN 0
#define SOFT_MASK_TABLE(align) \
. = ALIGN(align); \
__soft_mask_table : AT(ADDR(__soft_mask_table) - LOAD_OFFSET) { \
__start___soft_mask_table = .; \
KEEP(*(__soft_mask_table)) \
__stop___soft_mask_table = .; \
}
#define RESTART_TABLE(align) \
. = ALIGN(align); \
__restart_table : AT(ADDR(__restart_table) - LOAD_OFFSET) { \
@ -132,6 +140,7 @@ SECTIONS
RO_DATA(PAGE_SIZE)
#ifdef CONFIG_PPC64
SOFT_MASK_TABLE(8)
RESTART_TABLE(8)
. = ALIGN(8);

26
arch/powerpc/lib/restart_table.c
View File

@ -1,15 +1,41 @@
#include <asm/interrupt.h>
#include <asm/kprobes.h>
struct soft_mask_table_entry {
unsigned long start;
unsigned long end;
};
struct restart_table_entry {
unsigned long start;
unsigned long end;
unsigned long fixup;
};
extern struct soft_mask_table_entry __start___soft_mask_table[];
extern struct soft_mask_table_entry __stop___soft_mask_table[];
extern struct restart_table_entry __start___restart_table[];
extern struct restart_table_entry __stop___restart_table[];
/* Given an address, look for it in the soft mask table */
bool search_kernel_soft_mask_table(unsigned long addr)
{
struct soft_mask_table_entry *smte = __start___soft_mask_table;
while (smte < __stop___soft_mask_table) {
unsigned long start = smte->start;
unsigned long end = smte->end;
if (addr >= start && addr < end)
return true;
smte++;
}
return false;
}
NOKPROBE_SYMBOL(search_kernel_soft_mask_table);
/* Given an address, look for it in the kernel exception table */
unsigned long search_kernel_restart_table(unsigned long addr)
{