| Message ID | a49044c3833e40546f35dd1f821a683e6f4dfc1f.1715286093.git.namcao@linutronix.de (mailing list archive) |
|---|---|
| State | New |
| 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_FLASH_OFFSET. Instead, use __data_loc and > _sdata to do the same thing. > > While at it, also add a description for XIP_FIXUP_FLASH_OFFSET. > > Signed-off-by: Nam Cao <namcao@linutronix.de> > --- > arch/riscv/include/asm/xip_fixup.h | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/arch/riscv/include/asm/xip_fixup.h b/arch/riscv/include/asm/xip_fixup.h > index 9ed2cfae09e0..f3d56299bc22 100644 > --- a/arch/riscv/include/asm/xip_fixup.h > +++ b/arch/riscv/include/asm/xip_fixup.h > @@ -24,13 +24,21 @@ > sub \reg, \reg, t0 > .endm > .macro XIP_FIXUP_FLASH_OFFSET reg > + /* In linker script, at the transition from read-only section to > + * writable section, the VMA is increased while LMA remains the same. > + * (See in linker script how _sdata, __data_loc and LOAD_OFFSET is > + * changed) > + * > + * Consequently, early during boot before MMU is up, the generated code > + * reads the "writable" section at wrong addresses, because VMA is used > + * by compiler to generate code, but the data is located in Flash using > + * LMA. > + */ > + la t0, _sdata > + sub \reg, \reg, t0 > la t0, __data_loc > - REG_L t1, _xip_phys_offset > - sub \reg, \reg, t1 > add \reg, \reg, t0 > .endm > - > -_xip_phys_offset: .dword CONFIG_XIP_PHYS_ADDR + XIP_OFFSET > #else > .macro XIP_FIXUP_OFFSET reg > .endm 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 9ed2cfae09e0..f3d56299bc22 100644 --- a/arch/riscv/include/asm/xip_fixup.h +++ b/arch/riscv/include/asm/xip_fixup.h @@ -24,13 +24,21 @@ sub \reg, \reg, t0 .endm .macro XIP_FIXUP_FLASH_OFFSET reg + /* In linker script, at the transition from read-only section to + * writable section, the VMA is increased while LMA remains the same. + * (See in linker script how _sdata, __data_loc and LOAD_OFFSET is + * changed) + * + * Consequently, early during boot before MMU is up, the generated code + * reads the "writable" section at wrong addresses, because VMA is used + * by compiler to generate code, but the data is located in Flash using + * LMA. + */ + la t0, _sdata + sub \reg, \reg, t0 la t0, __data_loc - REG_L t1, _xip_phys_offset - sub \reg, \reg, t1 add \reg, \reg, t0 .endm - -_xip_phys_offset: .dword CONFIG_XIP_PHYS_ADDR + XIP_OFFSET #else .macro XIP_FIXUP_OFFSET reg .endm
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_FLASH_OFFSET. Instead, use __data_loc and _sdata to do the same thing. While at it, also add a description for XIP_FIXUP_FLASH_OFFSET. Signed-off-by: Nam Cao <namcao@linutronix.de> --- arch/riscv/include/asm/xip_fixup.h | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)