Thanks Marco for your detailed review!
On 2023/3/9 23:48, Marco Elver wrote:
On Thu, 9 Mar 2023 at 16:38, Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx> wrote:
Kfence only needs its pool to be mapped as page granularity, previous
judgement was a bit over protected. Decouple it from judgement and do
page granularity mapping for kfence pool only [1].
To implement this, also relocate the kfence pool allocation before the
linear mapping setting up, arm64_kfence_alloc_pool is to allocate phys
addr, __kfence_pool is to be set after linear mapping set up.
LINK: [1] https://lore.kernel.org/linux-arm-kernel/1675750519-1064-1-git-send-email-quic_zhenhuah@xxxxxxxxxxx/T/
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx>
---
arch/arm64/mm/mmu.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
arch/arm64/mm/pageattr.c | 5 ++---
include/linux/kfence.h | 7 +++++++
mm/kfence/core.c | 9 +++++++++
4 files changed, 62 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 6f9d889..46afe3f 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -24,6 +24,7 @@
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/set_memory.h>
+#include <linux/kfence.h>
#include <asm/barrier.h>
#include <asm/cputype.h>
@@ -525,6 +526,33 @@ static int __init enable_crash_mem_map(char *arg)
}
early_param("crashkernel", enable_crash_mem_map);
+#ifdef CONFIG_KFENCE
+
+static phys_addr_t arm64_kfence_alloc_pool(void)
+{
+ phys_addr_t kfence_pool = 0;
+
+ if (!kfence_sample_interval)
+ return 0;
+
+ kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE);
+ if (!kfence_pool) {
+ pr_err("failed to allocate kfence pool\n");
+ return 0;
+ }
+
+ return kfence_pool;
+}
+
+#else
+
+static phys_addr_t arm64_kfence_alloc_pool(void)
+{
+ return (phys_addr_t)NULL;
Just return "0" - which the above function does as well on error. Or
the above function should also do (phys_addr_t)NULL for consistency.
Done
+}
+
+#endif
+
static void __init map_mem(pgd_t *pgdp)
{
static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN);
@@ -532,6 +560,7 @@ static void __init map_mem(pgd_t *pgdp)
phys_addr_t kernel_end = __pa_symbol(__init_begin);
phys_addr_t start, end;
int flags = NO_EXEC_MAPPINGS;
+ phys_addr_t kfence_pool = 0;
u64 i;
/*
@@ -564,6 +593,10 @@ static void __init map_mem(pgd_t *pgdp)
}
#endif
+ kfence_pool = arm64_kfence_alloc_pool();
+ if (kfence_pool)
+ memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE);
+
/* map all the memory banks */
for_each_mem_range(i, &start, &end) {
if (start >= end)
@@ -608,6 +641,17 @@ static void __init map_mem(pgd_t *pgdp)
}
}
#endif
+
+ /* Kfence pool needs page-level mapping */
+ if (kfence_pool) {
+ __map_memblock(pgdp, kfence_pool,
+ kfence_pool + KFENCE_POOL_SIZE,
+ pgprot_tagged(PAGE_KERNEL),
+ NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
+ memblock_clear_nomap(kfence_pool, KFENCE_POOL_SIZE);
+ /* kfence_pool really mapped now */
+ kfence_set_pool(kfence_pool);
+ }
}
void mark_rodata_ro(void)
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 79dd201..61156d0 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -22,12 +22,11 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED
bool can_set_direct_map(void)
{
/*
- * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be
+ * rodata_full and DEBUG_PAGEALLOC require linear map to be
* mapped at page granularity, so that it is possible to
* protect/unprotect single pages.
*/
- return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() ||
- IS_ENABLED(CONFIG_KFENCE);
+ return (rodata_enabled && rodata_full) || debug_pagealloc_enabled();
}
static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
diff --git a/include/linux/kfence.h b/include/linux/kfence.h
index 726857a..d982ac2 100644
--- a/include/linux/kfence.h
+++ b/include/linux/kfence.h
@@ -64,6 +64,11 @@ static __always_inline bool is_kfence_address(const void *addr)
void __init kfence_alloc_pool(void);
/**
+ * kfence_set_pool() - KFENCE pool mapped and can be used
I don't understand the comment. Maybe just "allows an arch to set the
KFENCE pool during early init"
What I want to emphasize is __kfence_pool can be used now :)
Sure, your comment is more clear.
+ */
+void __init kfence_set_pool(phys_addr_t addr);
+
+/**
* kfence_init() - perform KFENCE initialization at boot time
*
* Requires that kfence_alloc_pool() was called before. This sets up the
@@ -222,8 +227,10 @@ bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *sla
#else /* CONFIG_KFENCE */
+#define KFENCE_POOL_SIZE 0
static inline bool is_kfence_address(const void *addr) { return false; }
static inline void kfence_alloc_pool(void) { }
+static inline void kfence_set_pool(phys_addr_t addr) { }
static inline void kfence_init(void) { }
static inline void kfence_shutdown_cache(struct kmem_cache *s) { }
static inline void *kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) { return NULL; }
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 5349c37..a17c20c2 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -814,12 +814,21 @@ void __init kfence_alloc_pool(void)
if (!kfence_sample_interval)
return;
+ /* if __kfence_pool already initialized in some arch, abort */
Abort sounds like it's a failure condition, but it's actually ok.
Maybe just write:
/* Check if the pool has already been initialized by arch; if so,
skip the below. */
Yes, your comment is more clear. Done.
+ if (__kfence_pool)
+ return;
+
__kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE);
if (!__kfence_pool)
pr_err("failed to allocate pool\n");
}
+void __init kfence_set_pool(phys_addr_t addr)
+{
+ __kfence_pool = phys_to_virt(addr);
+}
+
The rest looks good.
Updated patchset V 3 :)
