lkml.org 
[lkml]   [2020]   [Nov]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] arm64: scs: use vmapped IRQ and SDEI shadow stacks
On Thu, Oct 22, 2020 at 01:23:55PM -0700, Sami Tolvanen wrote:
> Use scs_alloc() to allocate also IRQ and SDEI shadow stacks instead of
> using statically allocated stacks.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
> arch/arm64/include/asm/scs.h | 21 ++++++++++-
> arch/arm64/kernel/entry.S | 6 ++--
> arch/arm64/kernel/irq.c | 2 ++
> arch/arm64/kernel/scs.c | 67 +++++++++++++++++++++++++++++++++---
> arch/arm64/kernel/sdei.c | 7 ++++
> include/linux/scs.h | 8 ++---
> kernel/scs.c | 4 +--
> 7 files changed, 101 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h
> index eaa2cd92e4c1..e9d2c3e67ff9 100644
> --- a/arch/arm64/include/asm/scs.h
> +++ b/arch/arm64/include/asm/scs.h
> @@ -24,6 +24,25 @@
> .endm
> #endif /* CONFIG_SHADOW_CALL_STACK */
>
> -#endif /* __ASSEMBLY __ */
> +#else /* __ASSEMBLY__ */
> +
> +#include <linux/scs.h>
> +
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +
> +extern void scs_init_irq(void);
> +
> +extern void scs_free_sdei(void);

This is only called on the scs_init_sdei() failure path, so it can be
static. But see below, because I think we should move all of these functions
out of scs.c anyway.

> diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
> index 9cf2fb87584a..54ba3725bc0e 100644
> --- a/arch/arm64/kernel/irq.c
> +++ b/arch/arm64/kernel/irq.c
> @@ -20,6 +20,7 @@
> #include <linux/seq_file.h>
> #include <linux/vmalloc.h>
> #include <asm/daifflags.h>
> +#include <asm/scs.h>
> #include <asm/vmap_stack.h>
>
> /* Only access this in an NMI enter/exit */
> @@ -54,6 +55,7 @@ static void init_irq_stacks(void)
> void __init init_IRQ(void)
> {
> init_irq_stacks();
> + scs_init_irq();

If we internalise this in init_irq_stacks()...

> diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
> index 7689f2031c0c..04519a7cb51d 100644
> --- a/arch/arm64/kernel/sdei.c
> +++ b/arch/arm64/kernel/sdei.c
> @@ -13,6 +13,7 @@
> #include <asm/kprobes.h>
> #include <asm/mmu.h>
> #include <asm/ptrace.h>
> +#include <asm/scs.h>
> #include <asm/sections.h>
> #include <asm/stacktrace.h>
> #include <asm/sysreg.h>
> @@ -138,6 +139,12 @@ unsigned long sdei_arch_get_entry_point(int conduit)
> return 0;
> }
>
> + if (scs_init_sdei()) {

... and this in init_sdei_stacks(), then I think we remove all of the code
from arch/arm64/kernel/scs.c.

> diff --git a/include/linux/scs.h b/include/linux/scs.h
> index 86e3c4b7b714..6b35a83576d4 100644
> --- a/include/linux/scs.h
> +++ b/include/linux/scs.h
> @@ -21,13 +21,11 @@
> /* An illegal pointer value to mark the end of the shadow stack. */
> #define SCS_END_MAGIC (0x5f6UL + POISON_POINTER_DELTA)
>
> -/* Allocate a static per-CPU shadow stack */
> -#define DEFINE_SCS(name) \
> - DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], name) \
> -
> #define task_scs(tsk) (task_thread_info(tsk)->scs_base)
> #define task_scs_sp(tsk) (task_thread_info(tsk)->scs_sp)
>
> +void *scs_alloc(int node);
> +void scs_free(void *s);
> void scs_init(void);
> int scs_prepare(struct task_struct *tsk, int node);
> void scs_release(struct task_struct *tsk);
> @@ -56,6 +54,8 @@ static inline bool task_scs_end_corrupted(struct task_struct *tsk)
>
> #else /* CONFIG_SHADOW_CALL_STACK */
>
> +static inline void *scs_alloc(int node) { return NULL; }
> +static inline void scs_free(void *s) {}
> static inline void scs_init(void) {}
> static inline void scs_task_reset(struct task_struct *tsk) {}
> static inline int scs_prepare(struct task_struct *tsk, int node) { return 0; }
> diff --git a/kernel/scs.c b/kernel/scs.c
> index 2136edba548d..8df4a92cd939 100644
> --- a/kernel/scs.c
> +++ b/kernel/scs.c
> @@ -24,7 +24,7 @@ static void __scs_account(void *s, int account)
> #define NR_CACHED_SCS 2
> static DEFINE_PER_CPU(void *, scs_cache[NR_CACHED_SCS]);
>
> -static void *scs_alloc(int node)
> +void *scs_alloc(int node)
> {
> int i;
> void *s;
> @@ -63,7 +63,7 @@ static void *scs_alloc(int node)
> return s;
> }
>
> -static void scs_free(void *s)
> +void scs_free(void *s)

Should be part of the first patch?

Will

\
 
 \ /
  Last update: 2020-11-19 14:13    [W:0.077 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site