| Message ID | 20210107123428.354231-3-alobakin@pm.me (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | MIPS: vmlinux.lds.S sections fixes & cleanup | expand |
On Thu, Jan 07, 2021 at 12:35:01PM +0000, Alexander Lobakin wrote: > Commit 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") added > -fno-asynchronous-unwind-tables to KBUILD_CFLAGS to prevent compiler > from emitting .eh_frame symbols. > However, as MIPS heavily uses CFI, that's not enough. Use the > approach taken for x86 (as it also uses CFI) and explicitly put CFI > symbols into the .debug_frame section (except for VDSO). > This allows us to drop .eh_frame from DISCARDS as it's no longer > being generated. > > Fixes: 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") > Suggested-by: Kees Cook <keescook@chromium.org> > Signed-off-by: Alexander Lobakin <alobakin@pm.me> Reviewed-by: Kees Cook <keescook@chromium.org>
On Thu, Jan 07, 2021 at 12:35:01PM +0000, Alexander Lobakin wrote: > Commit 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") added > -fno-asynchronous-unwind-tables to KBUILD_CFLAGS to prevent compiler > from emitting .eh_frame symbols. > However, as MIPS heavily uses CFI, that's not enough. Use the > approach taken for x86 (as it also uses CFI) and explicitly put CFI > symbols into the .debug_frame section (except for VDSO). > This allows us to drop .eh_frame from DISCARDS as it's no longer > being generated. > > Fixes: 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") > Suggested-by: Kees Cook <keescook@chromium.org> > Signed-off-by: Alexander Lobakin <alobakin@pm.me> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > --- > arch/mips/include/asm/asm.h | 18 ++++++++++++++++++ > arch/mips/kernel/vmlinux.lds.S | 1 - > 2 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/arch/mips/include/asm/asm.h b/arch/mips/include/asm/asm.h > index 3682d1a0bb80..908f6d6ae24b 100644 > --- a/arch/mips/include/asm/asm.h > +++ b/arch/mips/include/asm/asm.h > @@ -20,10 +20,27 @@ > #include <asm/sgidefs.h> > #include <asm/asm-eva.h> > > +#ifndef __VDSO__ > +/* > + * Emit CFI data in .debug_frame sections, not .eh_frame sections. > + * We don't do DWARF unwinding at runtime, so only the offline DWARF > + * information is useful to anyone. Note we should change this if we > + * ever decide to enable DWARF unwinding at runtime. > + */ > +#define CFI_SECTIONS .cfi_sections .debug_frame > +#else > + /* > + * For the vDSO, emit both runtime unwind information and debug > + * symbols for the .dbg file. > + */ > +#define CFI_SECTIONS > +#endif > + > /* > * LEAF - declare leaf routine > */ > #define LEAF(symbol) \ > + CFI_SECTIONS; \ > .globl symbol; \ > .align 2; \ > .type symbol, @function; \ > @@ -36,6 +53,7 @@ symbol: .frame sp, 0, ra; \ > * NESTED - declare nested routine entry point > */ > #define NESTED(symbol, framesize, rpc) \ > + CFI_SECTIONS; \ > .globl symbol; \ > .align 2; \ > .type symbol, @function; \ > diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S > index 16468957cba2..0f4e46ea4458 100644 > --- a/arch/mips/kernel/vmlinux.lds.S > +++ b/arch/mips/kernel/vmlinux.lds.S > @@ -225,6 +225,5 @@ SECTIONS > *(.options) > *(.pdr) > *(.reginfo) > - *(.eh_frame) > } > } > -- > 2.30.0 > >
diff --git a/arch/mips/include/asm/asm.h b/arch/mips/include/asm/asm.h index 3682d1a0bb80..908f6d6ae24b 100644 --- a/arch/mips/include/asm/asm.h +++ b/arch/mips/include/asm/asm.h @@ -20,10 +20,27 @@ #include <asm/sgidefs.h> #include <asm/asm-eva.h> +#ifndef __VDSO__ +/* + * Emit CFI data in .debug_frame sections, not .eh_frame sections. + * We don't do DWARF unwinding at runtime, so only the offline DWARF + * information is useful to anyone. Note we should change this if we + * ever decide to enable DWARF unwinding at runtime. + */ +#define CFI_SECTIONS .cfi_sections .debug_frame +#else + /* + * For the vDSO, emit both runtime unwind information and debug + * symbols for the .dbg file. + */ +#define CFI_SECTIONS +#endif + /* * LEAF - declare leaf routine */ #define LEAF(symbol) \ + CFI_SECTIONS; \ .globl symbol; \ .align 2; \ .type symbol, @function; \ @@ -36,6 +53,7 @@ symbol: .frame sp, 0, ra; \ * NESTED - declare nested routine entry point */ #define NESTED(symbol, framesize, rpc) \ + CFI_SECTIONS; \ .globl symbol; \ .align 2; \ .type symbol, @function; \ diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S index 16468957cba2..0f4e46ea4458 100644 --- a/arch/mips/kernel/vmlinux.lds.S +++ b/arch/mips/kernel/vmlinux.lds.S @@ -225,6 +225,5 @@ SECTIONS *(.options) *(.pdr) *(.reginfo) - *(.eh_frame) } }
Commit 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") added -fno-asynchronous-unwind-tables to KBUILD_CFLAGS to prevent compiler from emitting .eh_frame symbols. However, as MIPS heavily uses CFI, that's not enough. Use the approach taken for x86 (as it also uses CFI) and explicitly put CFI symbols into the .debug_frame section (except for VDSO). This allows us to drop .eh_frame from DISCARDS as it's no longer being generated. Fixes: 866b6a89c6d1 ("MIPS: Add DWARF unwinding to assembly") Suggested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Alexander Lobakin <alobakin@pm.me> --- arch/mips/include/asm/asm.h | 18 ++++++++++++++++++ arch/mips/kernel/vmlinux.lds.S | 1 - 2 files changed, 18 insertions(+), 1 deletion(-)