Message ID | 20200121192741.20597-1-geert+renesas@glider.be (mailing list archive) |
---|---|
State | Superseded |
Delegated to: | Geert Uytterhoeven |
Headers | show |
Series | ARM: boot: Obtain start of physical memory from DTB | expand |
On Tue, Jan 21, 2020 at 08:27:41PM +0100, Geert Uytterhoeven wrote: > Currently, the start address of physical memory is obtained by masking > the program counter with a fixed mask of 0xf8000000. This mask value > was chosen as a balance between the requirements of different platforms. > However, this does require that the start address of physical memory is > a multiple of 128 MiB, precluding booting Linux on platforms where this > requirement is not fulfilled. > > Fix this limitation by obtaining the start address from the passed DTB > instead, if available. Note that for now this is limited to DTBs passed > explicitly by the boot loader. DTBs appended to a zImage or uImage are > not inspected. Fall back to the traditional method when needed. > > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), > i.e. not at a multiple of 128 MiB. > > Suggested-by: Nicolas Pitre <nico@fluxnic.net> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Against arm/for-next. > > Tested with the following configurations: > - zImage + DTB (r8a7791/koelsch): physical memory start address > obtained from DT, > - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb): > physical memory start address obtained from DT, > - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g): physical > memory start address obtained by masking, as before. > > An appended DTB is currently processed after the start of physical > memory is obtained. Hence obtaining that address from an appended DTB > requires moving/copying that copy. Given the complexity w.r.t. the > "restart" label, and the lack of a need for me to support this, I didn't > implement that part. > --- > arch/arm/boot/compressed/Makefile | 6 ++- > arch/arm/boot/compressed/fdt_get_mem_start.c | 52 ++++++++++++++++++++ > arch/arm/boot/compressed/head.S | 16 +++++- > 3 files changed, 72 insertions(+), 2 deletions(-) > create mode 100644 arch/arm/boot/compressed/fdt_get_mem_start.c > > diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile > index da599c3a11934332..bbfecd648a1a3b57 100644 > --- a/arch/arm/boot/compressed/Makefile > +++ b/arch/arm/boot/compressed/Makefile > @@ -86,12 +86,15 @@ libfdt_objs := $(addsuffix .o, $(basename $(libfdt))) > $(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/% > $(call cmd,shipped) > > -$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \ > +$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o fdt_get_mem_start.o): \ > $(addprefix $(obj)/,$(libfdt_hdrs)) > > ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y) > OBJS += $(libfdt_objs) atags_to_fdt.o > endif > +ifeq ($(CONFIG_USE_OF),y) > +OBJS += $(libfdt_objs) fdt_get_mem_start.o > +endif > > targets := vmlinux vmlinux.lds piggy_data piggy.o \ > lib1funcs.o ashldi3.o bswapsdi2.o \ > @@ -116,6 +119,7 @@ CFLAGS_fdt.o := $(nossp-flags-y) > CFLAGS_fdt_ro.o := $(nossp-flags-y) > CFLAGS_fdt_rw.o := $(nossp-flags-y) > CFLAGS_fdt_wip.o := $(nossp-flags-y) > +CFLAGS_fdt_get_mem_start.o := $(nossp-flags-y) > > ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin -I$(obj) > asflags-y := -DZIMAGE > diff --git a/arch/arm/boot/compressed/fdt_get_mem_start.c b/arch/arm/boot/compressed/fdt_get_mem_start.c > new file mode 100644 > index 0000000000000000..2c5ac47f656317ee > --- /dev/null > +++ b/arch/arm/boot/compressed/fdt_get_mem_start.c > @@ -0,0 +1,52 @@ > +// SPDX-License-Identifier: GPL-2.0-only > + > +#include <libfdt.h> > + > +static const void *getprop(const void *fdt, const char *node_path, > + const char *property) > +{ > + int offset = fdt_path_offset(fdt, node_path); > + > + if (offset == -FDT_ERR_NOTFOUND) > + return NULL; > + > + return fdt_getprop(fdt, offset, property, NULL); > +} > + > +static uint32_t get_addr_size(const void *fdt) > +{ > + const __be32 *addr_len = getprop(fdt, "/", "#address-cells"); > + > + if (!addr_len) { > + /* default */ > + return 1; > + } > + > + return fdt32_to_cpu(*addr_len); > +} > + > +/* > + * Get the start of physical memory > + */ > + > +unsigned long fdt_get_mem_start(const void *fdt) > +{ > + const __be32 *memory; > + uint32_t addr_size; > + > + if (!fdt) > + return -1; > + > + if (*(__be32 *)fdt != cpu_to_fdt32(FDT_MAGIC)) > + return -1; > + > + /* Find the first memory node */ > + memory = getprop(fdt, "/memory", "reg"); > + if (!memory) > + return -1; > + > + /* There may be multiple cells on LPAE platforms */ > + addr_size = get_addr_size(fdt); > + > + return fdt32_to_cpu(memory[addr_size - 1]); > +} > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S > index 927f5dc413d7dff2..cb4e6a84b156c204 100644 > --- a/arch/arm/boot/compressed/head.S > +++ b/arch/arm/boot/compressed/head.S > @@ -235,8 +235,20 @@ not_angel: > .text > > #ifdef CONFIG_AUTO_ZRELADDR > +#ifdef CONFIG_USE_OF > /* > - * Find the start of physical memory. As we are executing > + * Find the start of physical memory. > + * Try the passed DTB first, if available. > + */ > + mov r0, r8 > + bl fdt_get_mem_start NAK. You don't have a stack setup here. The fact this works for you is merely due to "sp" happening to be pointing somewhere sane, but there is no such requirement. Therefore, this is fragile. > + mov r4, r0 > + cmn r0, #1 > + bne 1f > +#endif > + > + /* > + * Fall back to the traditional method. As we are executing > * without the MMU on, we are in the physical address space. > * We just need to get rid of any offset by aligning the > * address. > @@ -254,6 +266,8 @@ not_angel: > */ > mov r4, pc > and r4, r4, #0xf8000000 > + > +1: > /* Determine final kernel image address. */ > add r4, r4, #TEXT_OFFSET > #else > -- > 2.17.1 > >
On Tue, 21 Jan 2020, Geert Uytterhoeven wrote: > Currently, the start address of physical memory is obtained by masking > the program counter with a fixed mask of 0xf8000000. This mask value > was chosen as a balance between the requirements of different platforms. > However, this does require that the start address of physical memory is > a multiple of 128 MiB, precluding booting Linux on platforms where this > requirement is not fulfilled. > > Fix this limitation by obtaining the start address from the passed DTB > instead, if available. Note that for now this is limited to DTBs passed > explicitly by the boot loader. DTBs appended to a zImage or uImage are > not inspected. Fall back to the traditional method when needed. > > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), > i.e. not at a multiple of 128 MiB. > > Suggested-by: Nicolas Pitre <nico@fluxnic.net> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Against arm/for-next. > > Tested with the following configurations: > - zImage + DTB (r8a7791/koelsch): physical memory start address > obtained from DT, > - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb): > physical memory start address obtained from DT, > - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g): physical > memory start address obtained by masking, as before. > > An appended DTB is currently processed after the start of physical > memory is obtained. Hence obtaining that address from an appended DTB > requires moving/copying that copy. Given the complexity w.r.t. the > "restart" label, and the lack of a need for me to support this, I didn't > implement that part. Well, not exactly. You don't have to move anything. But more on that later. One important detail: you didn't set up the stack pointer. That means you're relying on whatever value left in sp by the bootloader. If you're lucky that might be fine, but it isn't a good idea to leave things to luck. Before calling the C code, you should probably do: adr r0, LC0 ldr r1, [r0] ldr sp, [r0, #28] sub r0, r0, r1 add sp, sp, r0 But if there is an appended dtb then you'll overwrite it. So you need to look for one and account for its size. Something like this: adr r0, LC0 ldr r1, [r0] @ get absolute LC0 ldr sp, [r0, #28] @ get stack location sub r1, r0, r1 @ compute relocation offset add sp, sp, r1 @ apply relocation #ifdef CONFIG_ARM_APPENDED_DTB /* * Look for an appended DTB. If found, use it and * move stack away from it. */ ldr r6, [r0, #12] @ get &_end add r6, r6, r1 @ relocate it ldmia r6, {r0, r5} @ get DTB signature and size #ifndef __ARMEB__ ldr r1, =0xedfe0dd0 @ sig is 0xd00dfeed big endian /* convert DTB size to little endian */ eor r2, r5, r5, ror #16 bic r2, r2, #0x00ff0000 mov r5, r5, ror #8 eor r5, r5, r2, lsr #8 #else ldr r1, =0xd00dfeed #endif cmp r0, r1 @ do we have a DTB there? moveq r8, r0 @ use it if so addeq sp, sp, r5 @ and move stack above it #endif bl fdt_get_mem_start ... This is a little involved but there is no way around that for a safe stack. Benefit is that you get appended DTB support with a single additional instruction. Also one minor nit: > + bl fdt_get_mem_start > + mov r4, r0 > + cmn r0, #1 Please just use "cmp r0 #-1" here. The assembler will convert it for you. Nicolas
Hi Nicolas, On Tue, Jan 21, 2020 at 11:44 PM Nicolas Pitre <nico@fluxnic.net> wrote: > On Tue, 21 Jan 2020, Geert Uytterhoeven wrote: > > Currently, the start address of physical memory is obtained by masking > > the program counter with a fixed mask of 0xf8000000. This mask value > > was chosen as a balance between the requirements of different platforms. > > However, this does require that the start address of physical memory is > > a multiple of 128 MiB, precluding booting Linux on platforms where this > > requirement is not fulfilled. > > > > Fix this limitation by obtaining the start address from the passed DTB > > instead, if available. Note that for now this is limited to DTBs passed > > explicitly by the boot loader. DTBs appended to a zImage or uImage are > > not inspected. Fall back to the traditional method when needed. > > > > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM > > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), > > i.e. not at a multiple of 128 MiB. > > > > Suggested-by: Nicolas Pitre <nico@fluxnic.net> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > > --- > > Against arm/for-next. > > > > Tested with the following configurations: > > - zImage + DTB (r8a7791/koelsch): physical memory start address > > obtained from DT, > > - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb): > > physical memory start address obtained from DT, > > - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g): physical > > memory start address obtained by masking, as before. > > > > An appended DTB is currently processed after the start of physical > > memory is obtained. Hence obtaining that address from an appended DTB > > requires moving/copying that copy. Given the complexity w.r.t. the > > "restart" label, and the lack of a need for me to support this, I didn't > > implement that part. > > Well, not exactly. You don't have to move anything. But more on that > later. > > One important detail: you didn't set up the stack pointer. That means > you're relying on whatever value left in sp by the bootloader. If you're > lucky that might be fine, but it isn't a good idea to leave things to > luck. > > Before calling the C code, you should probably do: > > adr r0, LC0 > ldr r1, [r0] > ldr sp, [r0, #28] > sub r0, r0, r1 > add sp, sp, r0 > > But if there is an appended dtb then you'll overwrite it. So you need > to look for one and account for its size. Thank you very much for the very constructive feedback! > Something like this: > > adr r0, LC0 > ldr r1, [r0] @ get absolute LC0 > ldr sp, [r0, #28] @ get stack location > sub r1, r0, r1 @ compute relocation offset > add sp, sp, r1 @ apply relocation > > #ifdef CONFIG_ARM_APPENDED_DTB > /* > * Look for an appended DTB. If found, use it and > * move stack away from it. > */ > ldr r6, [r0, #12] @ get &_end [r0, #12] is actually &_edata, not &_end. > add r6, r6, r1 @ relocate it > ldmia r6, {r0, r5} @ get DTB signature and size > #ifndef __ARMEB__ > ldr r1, =0xedfe0dd0 @ sig is 0xd00dfeed big endian > /* convert DTB size to little endian */ > eor r2, r5, r5, ror #16 > bic r2, r2, #0x00ff0000 > mov r5, r5, ror #8 > eor r5, r5, r2, lsr #8 > #else > ldr r1, =0xd00dfeed > #endif > cmp r0, r1 @ do we have a DTB there? > moveq r8, r0 @ use it if so moveq r8, r6 > addeq sp, sp, r5 @ and move stack above it Care must be taken to keep sp 64-bit aligned. > #endif > > bl fdt_get_mem_start > ... > > This is a little involved but there is no way around that for a safe > stack. Benefit is that you get appended DTB support with a single > additional instruction. True. > Also one minor nit: > > > + bl fdt_get_mem_start > > + mov r4, r0 > > + cmn r0, #1 > > Please just use "cmp r0 #-1" here. The assembler will convert it for > you. OK, thanks. Sent v2... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index da599c3a11934332..bbfecd648a1a3b57 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -86,12 +86,15 @@ libfdt_objs := $(addsuffix .o, $(basename $(libfdt))) $(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/% $(call cmd,shipped) -$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \ +$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o fdt_get_mem_start.o): \ $(addprefix $(obj)/,$(libfdt_hdrs)) ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y) OBJS += $(libfdt_objs) atags_to_fdt.o endif +ifeq ($(CONFIG_USE_OF),y) +OBJS += $(libfdt_objs) fdt_get_mem_start.o +endif targets := vmlinux vmlinux.lds piggy_data piggy.o \ lib1funcs.o ashldi3.o bswapsdi2.o \ @@ -116,6 +119,7 @@ CFLAGS_fdt.o := $(nossp-flags-y) CFLAGS_fdt_ro.o := $(nossp-flags-y) CFLAGS_fdt_rw.o := $(nossp-flags-y) CFLAGS_fdt_wip.o := $(nossp-flags-y) +CFLAGS_fdt_get_mem_start.o := $(nossp-flags-y) ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin -I$(obj) asflags-y := -DZIMAGE diff --git a/arch/arm/boot/compressed/fdt_get_mem_start.c b/arch/arm/boot/compressed/fdt_get_mem_start.c new file mode 100644 index 0000000000000000..2c5ac47f656317ee --- /dev/null +++ b/arch/arm/boot/compressed/fdt_get_mem_start.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <libfdt.h> + +static const void *getprop(const void *fdt, const char *node_path, + const char *property) +{ + int offset = fdt_path_offset(fdt, node_path); + + if (offset == -FDT_ERR_NOTFOUND) + return NULL; + + return fdt_getprop(fdt, offset, property, NULL); +} + +static uint32_t get_addr_size(const void *fdt) +{ + const __be32 *addr_len = getprop(fdt, "/", "#address-cells"); + + if (!addr_len) { + /* default */ + return 1; + } + + return fdt32_to_cpu(*addr_len); +} + +/* + * Get the start of physical memory + */ + +unsigned long fdt_get_mem_start(const void *fdt) +{ + const __be32 *memory; + uint32_t addr_size; + + if (!fdt) + return -1; + + if (*(__be32 *)fdt != cpu_to_fdt32(FDT_MAGIC)) + return -1; + + /* Find the first memory node */ + memory = getprop(fdt, "/memory", "reg"); + if (!memory) + return -1; + + /* There may be multiple cells on LPAE platforms */ + addr_size = get_addr_size(fdt); + + return fdt32_to_cpu(memory[addr_size - 1]); +} diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 927f5dc413d7dff2..cb4e6a84b156c204 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -235,8 +235,20 @@ not_angel: .text #ifdef CONFIG_AUTO_ZRELADDR +#ifdef CONFIG_USE_OF /* - * Find the start of physical memory. As we are executing + * Find the start of physical memory. + * Try the passed DTB first, if available. + */ + mov r0, r8 + bl fdt_get_mem_start + mov r4, r0 + cmn r0, #1 + bne 1f +#endif + + /* + * Fall back to the traditional method. As we are executing * without the MMU on, we are in the physical address space. * We just need to get rid of any offset by aligning the * address. @@ -254,6 +266,8 @@ not_angel: */ mov r4, pc and r4, r4, #0xf8000000 + +1: /* Determine final kernel image address. */ add r4, r4, #TEXT_OFFSET #else
Currently, the start address of physical memory is obtained by masking the program counter with a fixed mask of 0xf8000000. This mask value was chosen as a balance between the requirements of different platforms. However, this does require that the start address of physical memory is a multiple of 128 MiB, precluding booting Linux on platforms where this requirement is not fulfilled. Fix this limitation by obtaining the start address from the passed DTB instead, if available. Note that for now this is limited to DTBs passed explicitly by the boot loader. DTBs appended to a zImage or uImage are not inspected. Fall back to the traditional method when needed. This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), i.e. not at a multiple of 128 MiB. Suggested-by: Nicolas Pitre <nico@fluxnic.net> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- Against arm/for-next. Tested with the following configurations: - zImage + DTB (r8a7791/koelsch): physical memory start address obtained from DT, - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb): physical memory start address obtained from DT, - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g): physical memory start address obtained by masking, as before. An appended DTB is currently processed after the start of physical memory is obtained. Hence obtaining that address from an appended DTB requires moving/copying that copy. Given the complexity w.r.t. the "restart" label, and the lack of a need for me to support this, I didn't implement that part. --- arch/arm/boot/compressed/Makefile | 6 ++- arch/arm/boot/compressed/fdt_get_mem_start.c | 52 ++++++++++++++++++++ arch/arm/boot/compressed/head.S | 16 +++++- 3 files changed, 72 insertions(+), 2 deletions(-) create mode 100644 arch/arm/boot/compressed/fdt_get_mem_start.c