Re: [PATCH 1/5] arm: decompressor: set malloc pool size for the decompressor

From: Russell King - ARM Linux admin
Date: Mon Jun 01 2020 - 10:46:46 EST


On Mon, Jun 01, 2020 at 04:27:50PM +0200, Åukasz Stelmach wrote:
> Move the definition of malloc pool size of the decompressor to
> a single place. This value will be exposed later for kexec_file loader.
>
> Signed-off-by: Åukasz Stelmach <l.stelmach@xxxxxxxxxxx>
> ---
> arch/arm/boot/compressed/Makefile | 2 ++
> arch/arm/boot/compressed/head.S | 6 ++++--
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 9c11e7490292..b3594cd1588c 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -125,6 +125,8 @@ KBSS_SZ = $(shell echo $$(($$($(NM) $(obj)/../../../../vmlinux | \
> sed -n -e 's/^\([^ ]*\) [AB] __bss_start$$/-0x\1/p' \
> -e 's/^\([^ ]*\) [AB] __bss_stop$$/+0x\1/p') )) )
> LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ)
> +# malloc pool size
> +LDFLAGS_vmlinux += --defsym _malloc_size=0x10000
> # Supply ZRELADDR to the decompressor via a linker symbol.
> ifneq ($(CONFIG_AUTO_ZRELADDR),y)
> LDFLAGS_vmlinux += --defsym zreladdr=$(ZRELADDR)
> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> index e8e1c866e413..dcc1afa60fb9 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -309,7 +309,8 @@ restart: adr r0, LC0
> #ifndef CONFIG_ZBOOT_ROM
> /* malloc space is above the relocated stack (64k max) */
> add sp, sp, r0
> - add r10, sp, #0x10000
> + ldr r10, =_malloc_size
> + add r10, r10, sp

This says "locate _malloc_size in a literal pool somewhere, and load it
using a PC-relative offset". Are you sure that the literal pool is
sensibly located?

Would it be better to use a definition for this?

--
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