| Message ID | e18d9e8e3540098617d8f5b14859158a63b78594.1715286093.git.namcao@linutronix.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | remove size limit on XIP kernel | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/vmtest-fixes-PR | fail | merge-conflict |
On 10/05/2024 08:28, Nam Cao wrote: > XIP_OFFSET is the hard-coded offset of writable data section within the > kernel. > > By hard-coding this value, the read-only section of the kernel (which is > placed before the writable data section) is restricted in size. > > As a preparation to remove this hard-coded macro XIP_OFFSET entirely, stop > using XIP_OFFSET in XIP_FIXUP_OFFSET. Instead, use CONFIG_PHYS_RAM_BASE and > _sdata to do the same thing. > > While at it, also add a description for XIP_FIXUP_OFFSET. > > Signed-off-by: Nam Cao <namcao@linutronix.de> > --- > arch/riscv/include/asm/xip_fixup.h | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/include/asm/xip_fixup.h b/arch/riscv/include/asm/xip_fixup.h > index b65bf6306f69..9ed2cfae09e0 100644 > --- a/arch/riscv/include/asm/xip_fixup.h > +++ b/arch/riscv/include/asm/xip_fixup.h > @@ -9,8 +9,19 @@ > > #ifdef CONFIG_XIP_KERNEL > .macro XIP_FIXUP_OFFSET reg > - REG_L t0, _xip_fixup > + /* Fix-up address in Flash into address in RAM early during boot before > + * MMU is up. Because generated code "thinks" data is in Flash, but it > + * is actually in RAM (actually data is also in Flash, but Flash is > + * read-only, thus we need to use the data residing in RAM). > + * > + * The start of data in Flash is _sdata and the start of data in RAM is > + * CONFIG_PHYS_RAM_BASE. So this fix-up essentially does this: > + * reg += CONFIG_PHYS_RAM_BASE - _start > + */ > + li t0, CONFIG_PHYS_RAM_BASE > add \reg, \reg, t0 > + la t0, _sdata > + sub \reg, \reg, t0 > .endm > .macro XIP_FIXUP_FLASH_OFFSET reg > la t0, __data_loc > @@ -19,7 +30,6 @@ > add \reg, \reg, t0 > .endm > > -_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET > _xip_phys_offset: .dword CONFIG_XIP_PHYS_ADDR + XIP_OFFSET > #else > .macro XIP_FIXUP_OFFSET reg Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com> Thanks, Alex
diff --git a/arch/riscv/include/asm/xip_fixup.h b/arch/riscv/include/asm/xip_fixup.h index b65bf6306f69..9ed2cfae09e0 100644 --- a/arch/riscv/include/asm/xip_fixup.h +++ b/arch/riscv/include/asm/xip_fixup.h @@ -9,8 +9,19 @@ #ifdef CONFIG_XIP_KERNEL .macro XIP_FIXUP_OFFSET reg - REG_L t0, _xip_fixup + /* Fix-up address in Flash into address in RAM early during boot before + * MMU is up. Because generated code "thinks" data is in Flash, but it + * is actually in RAM (actually data is also in Flash, but Flash is + * read-only, thus we need to use the data residing in RAM). + * + * The start of data in Flash is _sdata and the start of data in RAM is + * CONFIG_PHYS_RAM_BASE. So this fix-up essentially does this: + * reg += CONFIG_PHYS_RAM_BASE - _start + */ + li t0, CONFIG_PHYS_RAM_BASE add \reg, \reg, t0 + la t0, _sdata + sub \reg, \reg, t0 .endm .macro XIP_FIXUP_FLASH_OFFSET reg la t0, __data_loc @@ -19,7 +30,6 @@ add \reg, \reg, t0 .endm -_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET _xip_phys_offset: .dword CONFIG_XIP_PHYS_ADDR + XIP_OFFSET #else .macro XIP_FIXUP_OFFSET reg
XIP_OFFSET is the hard-coded offset of writable data section within the kernel. By hard-coding this value, the read-only section of the kernel (which is placed before the writable data section) is restricted in size. As a preparation to remove this hard-coded macro XIP_OFFSET entirely, stop using XIP_OFFSET in XIP_FIXUP_OFFSET. Instead, use CONFIG_PHYS_RAM_BASE and _sdata to do the same thing. While at it, also add a description for XIP_FIXUP_OFFSET. Signed-off-by: Nam Cao <namcao@linutronix.de> --- arch/riscv/include/asm/xip_fixup.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)