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SubjectRe: [PATCH V3] ZBOOT: fix stack protector in compressed boot phase
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Hi Huacai,

On 2018-03-16 08:55, Huacai Chen wrote:
> Call __stack_chk_guard_setup() in decompress_kernel() is too late that
> stack checking always fails for decompress_kernel() itself. So remove
> __stack_chk_guard_setup() and initialize __stack_chk_guard before we
> call decompress_kernel().
>
> Original code comes from ARM but also used for MIPS and SH, so fix them
> together. If without this fix, compressed booting of these archs will
> fail because stack checking is enabled by default (>=4.16).
>
> V2: Fix build on ARM.
> V3: Fix build on SuperH.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Huacai Chen <chenhc@lemote.com>

This patch breaks booting on ARM Exynos4210 based boards (tested with
next-20180323, exynos_defconfig, both Trats and Origen fails to boot).
That's a bit strange, because all other Exynos SoC works fine (I've
checked 3250, 4412, 5250, 5410 and 542x). I really have no idea what
is so specific inc case of Exynos4210, that causes this failure.

> ---
> arch/arm/boot/compressed/head.S | 4 ++++
> arch/arm/boot/compressed/misc.c | 7 -------
> arch/mips/boot/compressed/decompress.c | 7 -------
> arch/mips/boot/compressed/head.S | 4 ++++
> arch/sh/boot/compressed/head_32.S | 8 ++++++++
> arch/sh/boot/compressed/head_64.S | 4 ++++
> arch/sh/boot/compressed/misc.c | 7 -------
> 7 files changed, 20 insertions(+), 21 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> index 45c8823..bae1fc6 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -547,6 +547,10 @@ not_relocated: mov r0, #0
> bic r4, r4, #1
> blne cache_on
>
> + ldr r0, =__stack_chk_guard
> + ldr r1, =0x000a0dff
> + str r1, [r0]
> +
> /*
> * The C runtime environment should now be setup sufficiently.
> * Set up some pointers, and start decompressing.
> diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
> index 16a8a80..e518ef5 100644
> --- a/arch/arm/boot/compressed/misc.c
> +++ b/arch/arm/boot/compressed/misc.c
> @@ -130,11 +130,6 @@ asmlinkage void __div0(void)
>
> unsigned long __stack_chk_guard;
>
> -void __stack_chk_guard_setup(void)
> -{
> - __stack_chk_guard = 0x000a0dff;
> -}
> -
> void __stack_chk_fail(void)
> {
> error("stack-protector: Kernel stack is corrupted\n");
> @@ -150,8 +145,6 @@ decompress_kernel(unsigned long output_start, unsigned long free_mem_ptr_p,
> {
> int ret;
>
> - __stack_chk_guard_setup();
> -
> output_data = (unsigned char *)output_start;
> free_mem_ptr = free_mem_ptr_p;
> free_mem_end_ptr = free_mem_ptr_end_p;
> diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
> index fdf99e9..5ba431c 100644
> --- a/arch/mips/boot/compressed/decompress.c
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -78,11 +78,6 @@ void error(char *x)
>
> unsigned long __stack_chk_guard;
>
> -void __stack_chk_guard_setup(void)
> -{
> - __stack_chk_guard = 0x000a0dff;
> -}
> -
> void __stack_chk_fail(void)
> {
> error("stack-protector: Kernel stack is corrupted\n");
> @@ -92,8 +87,6 @@ void decompress_kernel(unsigned long boot_heap_start)
> {
> unsigned long zimage_start, zimage_size;
>
> - __stack_chk_guard_setup();
> -
> zimage_start = (unsigned long)(&__image_begin);
> zimage_size = (unsigned long)(&__image_end) -
> (unsigned long)(&__image_begin);
> diff --git a/arch/mips/boot/compressed/head.S b/arch/mips/boot/compressed/head.S
> index 409cb48..00d0ee0 100644
> --- a/arch/mips/boot/compressed/head.S
> +++ b/arch/mips/boot/compressed/head.S
> @@ -32,6 +32,10 @@ start:
> bne a2, a0, 1b
> addiu a0, a0, 4
>
> + PTR_LA a0, __stack_chk_guard
> + PTR_LI a1, 0x000a0dff
> + sw a1, 0(a0)
> +
> PTR_LA a0, (.heap) /* heap address */
> PTR_LA sp, (.stack + 8192) /* stack address */
>
> diff --git a/arch/sh/boot/compressed/head_32.S b/arch/sh/boot/compressed/head_32.S
> index 7bb1681..e84237d 100644
> --- a/arch/sh/boot/compressed/head_32.S
> +++ b/arch/sh/boot/compressed/head_32.S
> @@ -76,6 +76,10 @@ l1:
> mov.l init_stack_addr, r0
> mov.l @r0, r15
>
> + mov.l __stack_chk_guard_addr, r0
> + mov.l __stack_chk_guard_val, r1
> + mov.l r1, @r0
> +
> /* Decompress the kernel */
> mov.l decompress_kernel_addr, r0
> jsr @r0
> @@ -97,6 +101,10 @@ kexec_magic:
> .long 0x400000F0 /* magic used by kexec to parse zImage format */
> init_stack_addr:
> .long stack_start
> +__stack_chk_guard_val:
> + .long 0x000A0DFF
> +__stack_chk_guard_addr:
> + .long __stack_chk_guard
> decompress_kernel_addr:
> .long decompress_kernel
> kernel_start_addr:
> diff --git a/arch/sh/boot/compressed/head_64.S b/arch/sh/boot/compressed/head_64.S
> index 9993113..8b4d540 100644
> --- a/arch/sh/boot/compressed/head_64.S
> +++ b/arch/sh/boot/compressed/head_64.S
> @@ -132,6 +132,10 @@ startup:
> addi r22, 4, r22
> bne r22, r23, tr1
>
> + movi datalabel __stack_chk_guard, r0
> + movi 0x000a0dff, r1
> + st.l r0, 0, r1
> +
> /*
> * Decompress the kernel.
> */
> diff --git a/arch/sh/boot/compressed/misc.c b/arch/sh/boot/compressed/misc.c
> index 627ce8e..fe4c079 100644
> --- a/arch/sh/boot/compressed/misc.c
> +++ b/arch/sh/boot/compressed/misc.c
> @@ -106,11 +106,6 @@ static void error(char *x)
>
> unsigned long __stack_chk_guard;
>
> -void __stack_chk_guard_setup(void)
> -{
> - __stack_chk_guard = 0x000a0dff;
> -}
> -
> void __stack_chk_fail(void)
> {
> error("stack-protector: Kernel stack is corrupted\n");
> @@ -130,8 +125,6 @@ void decompress_kernel(void)
> {
> unsigned long output_addr;
>
> - __stack_chk_guard_setup();
> -
> #ifdef CONFIG_SUPERH64
> output_addr = (CONFIG_MEMORY_START + 0x2000);
> #else

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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