| Message ID | 20200521165641.15940-6-kristen@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Function Granular KASLR | expand |
On Thu, May 21, 2020 at 09:56:36AM -0700, Kristen Carlson Accardi wrote: > When using -ffunction-sections to place each function in > it's own text section so it can be randomized at load time, the > linker considers these .text.* sections "orphaned sections", and > will place them after the first similar section (.text). In order > to accurately represent the end of the text section and the > orphaned sections, _etext must be moved so that it is after both > .text and .text.* The text size must also be calculated to > include .text AND .text.* > > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > Tested-by: Tony Luck <tony.luck@intel.com> > --- > arch/x86/kernel/vmlinux.lds.S | 18 +++++++++++++++++- > include/asm-generic/vmlinux.lds.h | 2 +- > 2 files changed, 18 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 1bf7e312361f..044f7528a2f0 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -147,8 +147,24 @@ SECTIONS > #endif > } :text =0xcccc > > - /* End of text section, which should occupy whole number of pages */ > +#ifdef CONFIG_FG_KASLR > + /* > + * -ffunction-sections creates .text.* sections, which are considered > + * "orphan sections" and added after the first similar section (.text). > + * Adding this ALIGN statement causes the address of _etext > + * to be below that of all the .text.* orphaned sections > + */ > + . = ALIGN(PAGE_SIZE); > +#endif > _etext = .; > + > + /* > + * the size of the .text section is used to calculate the address > + * range for orc lookups. If we just use SIZEOF(.text), we will > + * miss all the .text.* sections. Calculate the size using _etext > + * and _stext and save the value for later. > + */ > + text_size = _etext - _stext; > . = ALIGN(PAGE_SIZE); I don't think there's any need for this #ifdef (nor the trailing ALIGN). I think leave the comment to explain why the ALIGN is being moved before the _etext. A repeated ALIGN won't move the position: --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -147,9 +147,11 @@ SECTIONS #endif } :text =0xcccc + . = ALIGN(PAGE_SIZE); /* End of text section, which should occupy whole number of * pages */ _etext = .; . = ALIGN(PAGE_SIZE); + _ktext = .; X86_ALIGN_RODATA_BEGIN RO_DATA(PAGE_SIZE) $ nm vmlinux | grep '_[ek]text' ffffffff81e02000 R _etext ffffffff81e02000 R _ktext
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 1bf7e312361f..044f7528a2f0 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -147,8 +147,24 @@ SECTIONS #endif } :text =0xcccc - /* End of text section, which should occupy whole number of pages */ +#ifdef CONFIG_FG_KASLR + /* + * -ffunction-sections creates .text.* sections, which are considered + * "orphan sections" and added after the first similar section (.text). + * Adding this ALIGN statement causes the address of _etext + * to be below that of all the .text.* orphaned sections + */ + . = ALIGN(PAGE_SIZE); +#endif _etext = .; + + /* + * the size of the .text section is used to calculate the address + * range for orc lookups. If we just use SIZEOF(.text), we will + * miss all the .text.* sections. Calculate the size using _etext + * and _stext and save the value for later. + */ + text_size = _etext - _stext; . = ALIGN(PAGE_SIZE); X86_ALIGN_RODATA_BEGIN diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 71e387a5fe90..f5baee74854c 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -813,7 +813,7 @@ . = ALIGN(4); \ .orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \ orc_lookup = .; \ - . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \ + . += (((text_size + LOOKUP_BLOCK_SIZE - 1) / \ LOOKUP_BLOCK_SIZE) + 1) * 4; \ orc_lookup_end = .; \ }