Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for fsl_booke64
From: Christophe Leroy
Date: Thu Feb 20 2020 - 08:48:29 EST
Le 06/02/2020 Ã 03:58, Jason Yan a ÃcritÂ:
The implementation for Freescale BookE64 is similar as BookE32. One
difference is that Freescale BookE64 set up a TLB mapping of 1G during
booting. Another difference is that ppc64 needs the kernel to be
64K-aligned. So we can randomize the kernel in this 1G mapping and make
it 64K-aligned. This can save some code to creat another TLB map at
early boot. The disadvantage is that we only have about 1G/64K = 16384
slots to put the kernel in.
To support secondary cpu boot up, a variable __kaslr_offset was added in
first_256B section. This can help secondary cpu get the kaslr offset
before the 1:1 mapping has been setup.
Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
Cc: Scott Wood <oss@xxxxxxxxxxxx>
Cc: Diana Craciun <diana.craciun@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/powerpc/Kconfig | 2 +-
arch/powerpc/kernel/exceptions-64e.S | 10 +++++++++
arch/powerpc/kernel/head_64.S | 7 ++++++
arch/powerpc/kernel/setup_64.c | 4 +++-
arch/powerpc/mm/mmu_decl.h | 16 +++++++-------
arch/powerpc/mm/nohash/kaslr_booke.c | 33 +++++++++++++++++++++++++---
6 files changed, 59 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c150a9d49343..754aeb96bb1c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -568,7 +568,7 @@ config RELOCATABLE
config RANDOMIZE_BASE
bool "Randomize the address of the kernel image"
- depends on (FSL_BOOKE && FLATMEM && PPC32)
+ depends on (PPC_FSL_BOOK3E && FLATMEM)
depends on RELOCATABLE
help
Randomizes the virtual address at which the kernel image is
diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 1b9b174bee86..c1c05b8684ca 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -1378,6 +1378,7 @@ skpinv: addi r6,r6,1 /* Increment */
1: mflr r6
addi r6,r6,(2f - 1b)
tovirt(r6,r6)
+ add r6,r6,r19
lis r7,MSR_KERNEL@h
ori r7,r7,MSR_KERNEL@l
mtspr SPRN_SRR0,r6
@@ -1400,6 +1401,7 @@ skpinv: addi r6,r6,1 /* Increment */
/* We translate LR and return */
tovirt(r8,r8)
+ add r8,r8,r19
mtlr r8
blr
@@ -1528,6 +1530,7 @@ a2_tlbinit_code_end:
*/
_GLOBAL(start_initialization_book3e)
mflr r28
+ li r19, 0
/* First, we need to setup some initial TLBs to map the kernel
* text, data and bss at PAGE_OFFSET. We don't have a real mode
@@ -1570,6 +1573,12 @@ _GLOBAL(book3e_secondary_core_init)
cmplwi r4,0
bne 2f
+ li r19, 0
+#ifdef CONFIG_RANDOMIZE_BASE
+ LOAD_REG_ADDR_PIC(r19, __kaslr_offset)
+ lwz r19,0(r19)
+ rlwinm r19,r19,0,0,5
+#endif
/* Setup TLB for this core */
bl initial_tlb_book3e
@@ -1602,6 +1611,7 @@ _GLOBAL(book3e_secondary_core_init)
lis r3,PAGE_OFFSET@highest
sldi r3,r3,32
or r28,r28,r3
+ add r28,r28,r19
1: mtlr r28
blr
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index ad79fddb974d..744624140fb8 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -104,6 +104,13 @@ __secondary_hold_acknowledge:
.8byte 0x0
#ifdef CONFIG_RELOCATABLE
+#ifdef CONFIG_RANDOMIZE_BASE
+ . = 0x58
+ .globl __kaslr_offset
+__kaslr_offset:
+DEFINE_FIXED_SYMBOL(__kaslr_offset)
+ .long 0
+#endif
/* This flag is set to 1 by a loader if the kernel should run
* at the loaded address instead of the linked address. This
* is used by kexec-tools to keep the the kdump kernel in the
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 6104917a282d..a16b970a8d1a 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -66,7 +66,7 @@
#include <asm/feature-fixups.h>
#include <asm/kup.h>
#include <asm/early_ioremap.h>
-
Why remove this new line which clearly separates things in asm/ and
things in local dir ?
+#include <mm/mmu_decl.h>
#include "setup.h"
int spinning_secondaries;
@@ -300,6 +300,8 @@ void __init early_setup(unsigned long dt_ptr)
/* Enable early debugging if any specified (see udbg.h) */
udbg_early_init();
+ kaslr_early_init(__va(dt_ptr), 0);
+
udbg_printf(" -> %s(), dt_ptr: 0x%lx\n", __func__, dt_ptr);
/*
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index 3e1c85c7d10b..bbd721d1e3d7 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -147,14 +147,6 @@ void reloc_kernel_entry(void *fdt, long addr);
extern void loadcam_entry(unsigned int index);
extern void loadcam_multi(int first_idx, int num, int tmp_idx);
-#ifdef CONFIG_RANDOMIZE_BASE
-void kaslr_early_init(void *dt_ptr, phys_addr_t size);
-void kaslr_late_init(void);
-#else
-static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
-static inline void kaslr_late_init(void) {}
-#endif
-
struct tlbcam {
u32 MAS0;
u32 MAS1;
@@ -164,6 +156,14 @@ struct tlbcam {
};
#endif
+#ifdef CONFIG_RANDOMIZE_BASE
+void kaslr_early_init(void *dt_ptr, phys_addr_t size);
+void kaslr_late_init(void);
+#else
+static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
+static inline void kaslr_late_init(void) {}
+#endif
+
#if defined(CONFIG_PPC_BOOK3S_32) || defined(CONFIG_FSL_BOOKE) || defined(CONFIG_PPC_8xx)
/* 6xx have BATS */
/* FSL_BOOKE have TLBCAM */
diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
index 07b036e98353..c6f5c1db1394 100644
--- a/arch/powerpc/mm/nohash/kaslr_booke.c
+++ b/arch/powerpc/mm/nohash/kaslr_booke.c
@@ -231,7 +231,7 @@ static __init unsigned long get_usable_address(const void *fdt,
unsigned long pa;
unsigned long pa_end;
- for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) {
+ for (pa = offset; (long)pa > (long)start; pa -= SZ_64K) {
Doesn't this modify the behaviour for PPC32 too ?
pa_end = pa + regions.kernel_size;
if (overlaps_region(fdt, pa, pa_end))
continue;
@@ -265,14 +265,14 @@ static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long rando
{
unsigned long koffset = 0;
unsigned long start;
- unsigned long index;
unsigned long offset;
+#ifdef CONFIG_PPC32
Can we use
if (IS_ENABLED(CONFIG_PPC32)) {
/* 32 bits stuff */
} else {
/* 64 bits stuff */
}
/*
* Decide which 64M we want to start
* Only use the low 8 bits of the random seed
*/
- index = random & 0xFF;
+ unsigned long index = random & 0xFF;
That's not good in terms of readability, index declaration should remain
at the top of the function, should be possible if using IS_ENABLED() instead
index %= regions.linear_sz / SZ_64M;
/* Decide offset inside 64M */
@@ -287,6 +287,15 @@ static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long rando
break;
index--;
}
+#else
+ /* Decide kernel offset inside 1G */
+ offset = random % (SZ_1G - regions.kernel_size);
+ offset = round_down(offset, SZ_64K);
+
+ start = memstart_addr;
+ offset = memstart_addr + offset;
+ koffset = get_usable_address(dt_ptr, start, offset);
+#endif
if (koffset != 0)
koffset -= memstart_addr;
@@ -325,6 +334,7 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
else
pr_warn("KASLR: No safe seed for randomizing the kernel base.\n");
+#ifdef CONFIG_PPC32
ram = min_t(phys_addr_t, __max_low_memory, size);
ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true);
linear_sz = min_t(unsigned long, ram, SZ_512M);
@@ -332,6 +342,7 @@ static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size
/* If the linear size is smaller than 64M, do not randmize */
if (linear_sz < SZ_64M)
return 0;
+#endif
/* check for a reserved-memory node and record its cell sizes */
regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory");
@@ -363,6 +374,17 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
unsigned long offset;
unsigned long kernel_sz;
+#ifdef CONFIG_PPC64
Same, can we use a standard C if/else sequence with
IS_ENABLED(CONFIG_PPC64) ?
+ unsigned int *__kaslr_offset = (unsigned int *)(KERNELBASE + 0x58);
+ unsigned int *__run_at_load = (unsigned int *)(KERNELBASE + 0x5c);
+
+ if (*__run_at_load == 1)
+ return;
+
+ /* Setup flat device-tree pointer */
+ initial_boot_params = dt_ptr;
+#endif
+
kernel_sz = (unsigned long)_end - (unsigned long)_stext;
offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
@@ -372,6 +394,7 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
kernstart_virt_addr += offset;
kernstart_addr += offset;
+#ifdef CONFIG_PPC32
is_second_reloc = 1;
if (offset >= SZ_64M) {
@@ -381,6 +404,10 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
/* Create kernel map to relocate in */
create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
}
+#else
+ *__kaslr_offset = kernstart_virt_addr - KERNELBASE;
+ *__run_at_load = 1;
+#endif
/* Copy the kernel to it's new location and run */
memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz);
Christophe