mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 04:35:20 +07:00
6fffacb303
It supposed to be safe to modify static branches after jump_label_init().
But, because static key modifying code eventually calls text_poke() it can
end up accessing a struct page which has not been initialized yet.
Here is how to quickly reproduce the problem. Insert code like this
into init/main.c:
| +static DEFINE_STATIC_KEY_FALSE(__test);
| asmlinkage __visible void __init start_kernel(void)
| {
| char *command_line;
|@@ -587,6 +609,10 @@ asmlinkage __visible void __init start_kernel(void)
| vfs_caches_init_early();
| sort_main_extable();
| trap_init();
|+ {
|+ static_branch_enable(&__test);
|+ WARN_ON(!static_branch_likely(&__test));
|+ }
| mm_init();
The following warnings show-up:
WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:701 text_poke+0x20d/0x230
RIP: 0010:text_poke+0x20d/0x230
Call Trace:
? text_poke_bp+0x50/0xda
? arch_jump_label_transform+0x89/0xe0
? __jump_label_update+0x78/0xb0
? static_key_enable_cpuslocked+0x4d/0x80
? static_key_enable+0x11/0x20
? start_kernel+0x23e/0x4c8
? secondary_startup_64+0xa5/0xb0
---[ end trace abdc99c031b8a90a ]---
If the code above is moved after mm_init(), no warning is shown, as struct
pages are initialized during handover from memblock.
Use text_poke_early() in static branching until early boot IRQs are enabled
and from there switch to text_poke. Also, ensure text_poke() is never
invoked when unitialized memory access may happen by using adding a
!after_bootmem assertion.
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-9-pasha.tatashin@oracle.com
43 lines
1.5 KiB
C
43 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_X86_TEXT_PATCHING_H
|
|
#define _ASM_X86_TEXT_PATCHING_H
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/stddef.h>
|
|
#include <asm/ptrace.h>
|
|
|
|
struct paravirt_patch_site;
|
|
#ifdef CONFIG_PARAVIRT
|
|
void apply_paravirt(struct paravirt_patch_site *start,
|
|
struct paravirt_patch_site *end);
|
|
#else
|
|
static inline void apply_paravirt(struct paravirt_patch_site *start,
|
|
struct paravirt_patch_site *end)
|
|
{}
|
|
#define __parainstructions NULL
|
|
#define __parainstructions_end NULL
|
|
#endif
|
|
|
|
extern void *text_poke_early(void *addr, const void *opcode, size_t len);
|
|
|
|
/*
|
|
* Clear and restore the kernel write-protection flag on the local CPU.
|
|
* Allows the kernel to edit read-only pages.
|
|
* Side-effect: any interrupt handler running between save and restore will have
|
|
* the ability to write to read-only pages.
|
|
*
|
|
* Warning:
|
|
* Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
|
|
* no thread can be preempted in the instructions being modified (no iret to an
|
|
* invalid instruction possible) or if the instructions are changed from a
|
|
* consistent state to another consistent state atomically.
|
|
* On the local CPU you need to be protected again NMI or MCE handlers seeing an
|
|
* inconsistent instruction while you patch.
|
|
*/
|
|
extern void *text_poke(void *addr, const void *opcode, size_t len);
|
|
extern int poke_int3_handler(struct pt_regs *regs);
|
|
extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
|
|
extern int after_bootmem;
|
|
|
|
#endif /* _ASM_X86_TEXT_PATCHING_H */
|