[edk2-devel] [PATCH v2] BaseTools/GenFw: Correct offset when relocating an ADR

[edk2-devel] [PATCH v2] BaseTools/GenFw: Correct offset when relocating an ADR

[Jake Garver via groups.io]

In the R_AARCH64_ADR_GOT_PAGE case on AARCH64, we may encounter an ADR
instead of an ADRP when the toolchain is working around Cortex-A53
erratum #843419.  If that's the case, be sure to calculate the offset
appropriately.

This resolves an issue experienced when building a StandaloneMm image
with stack protection enabled on GCC compiled with
"--enable-fix-cortex-a53-843419".  This scenario sometimes generates an
ADR with a R_AARCH64_ADR_GOT_PAGE relocation.

In this scenario, the following code is being generated by the
toolchain:

    # Load to set the stack canary
    2ffc:	10028020 	adr	x0, 8000 <mErrorString+0x1bc>
    3008:	f940d400 	ldr	x0, [x0, #424]

    # Load to check the stack canary
    30cc:	b0000020 	adrp	x0, 8000 <mErrorString+0x1bc>
    30d0:	f940d400 	ldr	x0, [x0, #424]

GenFw rewrote that to:

    # Load to set the stack canary
    2ffc:	10000480 	adr	x0, 0x308c
    3008:	912ec000 	add	x0, x0, #0xbb0

    # Load to check the stack canary
    30cc:	f0000460 	adrp	x0, 0x92000
    30d0:	912ec000 	add	x0, x0, #0xbb0

Note that we're now setting the stack canary from the wrong address,
resulting in an erroneous stack fault.

After this fix, the offset will be calculated correctly for an ADR and
the stack canary is set correctly.

Signed-off-by: Jake Garver <jake@nvidia.com>
---

Notes:
  v2: Implement approach proposed by Ard Biesheuvel.
    - title changed to: Correct offset when relocating an ADR
  v1: Original title: Change opcode when converting ADR to ADRP

 BaseTools/Source/C/GenFw/Elf64Convert.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c b/BaseTools/Source/C/GenFw/Elf64Convert.c
index 9911db65af..9d04fc612e 100644
--- a/BaseTools/Source/C/GenFw/Elf64Convert.c
+++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
@@ -1562,7 +1562,27 @@ WriteSections64 (
             // subsequent LDR instruction (covered by a R_AARCH64_LD64_GOT_LO12_NC
             // relocation) into an ADD instruction - this is handled above.
             //
-            Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
+            // In order to handle Cortex-A53 erratum #843419, the GCC toolchain
+            // may convert an ADRP instruction at the end of a page (0xffc
+            // offset) into an ADR instruction. If so, be sure to calculate the
+            // offset for an ADR instead of ADRP.
+            //
+            if ((*(UINT32 *)Targ & BIT31) == 0) {
+              //
+              // Calculate the offset for an ADR.
+              //
+              Offset = (Sym->st_value & ~0xfff) - Rel->r_offset;
+              if (Offset < -0x100000 || Offset > 0xfffff) {
+                Error (NULL, 0, 3000, "Invalid", "WriteSections64(): %s  due to its size (> 1 MB), unable to relocate ADR.",
+                  mInImageName);
+                break;
+              }
+            } else {
+              //
+              // Calculate the offset for an ADRP.
+              //
+              Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
+            }
 
             *(UINT32 *)Targ &= 0x9000001f;
             *(UINT32 *)Targ |= ((Offset & 0x1ffffc) << (5 - 2)) | ((Offset & 0x3) << 29);
-- 
2.34.1



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Re: [edk2-devel] [PATCH v2] BaseTools/GenFw: Correct offset when relocating an ADR

[Rebecca Cran]

Reviewed-by: Rebecca Cran <rebecca@bsdio.com>


On 12/20/2023 12:31 PM, Jake Garver wrote:
> In the R_AARCH64_ADR_GOT_PAGE case on AARCH64, we may encounter an ADR
> instead of an ADRP when the toolchain is working around Cortex-A53
> erratum #843419.  If that's the case, be sure to calculate the offset
> appropriately.
>
> This resolves an issue experienced when building a StandaloneMm image
> with stack protection enabled on GCC compiled with
> "--enable-fix-cortex-a53-843419".  This scenario sometimes generates an
> ADR with a R_AARCH64_ADR_GOT_PAGE relocation.
>
> In this scenario, the following code is being generated by the
> toolchain:
>
>      # Load to set the stack canary
>      2ffc:	10028020 	adr	x0, 8000 <mErrorString+0x1bc>
>      3008:	f940d400 	ldr	x0, [x0, #424]
>
>      # Load to check the stack canary
>      30cc:	b0000020 	adrp	x0, 8000 <mErrorString+0x1bc>
>      30d0:	f940d400 	ldr	x0, [x0, #424]
>
> GenFw rewrote that to:
>
>      # Load to set the stack canary
>      2ffc:	10000480 	adr	x0, 0x308c
>      3008:	912ec000 	add	x0, x0, #0xbb0
>
>      # Load to check the stack canary
>      30cc:	f0000460 	adrp	x0, 0x92000
>      30d0:	912ec000 	add	x0, x0, #0xbb0
>
> Note that we're now setting the stack canary from the wrong address,
> resulting in an erroneous stack fault.
>
> After this fix, the offset will be calculated correctly for an ADR and
> the stack canary is set correctly.
>
> Signed-off-by: Jake Garver <jake@nvidia.com>
> ---
>
> Notes:
>    v2: Implement approach proposed by Ard Biesheuvel.
>      - title changed to: Correct offset when relocating an ADR
>    v1: Original title: Change opcode when converting ADR to ADRP
>
>   BaseTools/Source/C/GenFw/Elf64Convert.c | 22 +++++++++++++++++++++-
>   1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c b/BaseTools/Source/C/GenFw/Elf64Convert.c
> index 9911db65af..9d04fc612e 100644
> --- a/BaseTools/Source/C/GenFw/Elf64Convert.c
> +++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
> @@ -1562,7 +1562,27 @@ WriteSections64 (
>               // subsequent LDR instruction (covered by a R_AARCH64_LD64_GOT_LO12_NC
>               // relocation) into an ADD instruction - this is handled above.
>               //
> -            Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
> +            // In order to handle Cortex-A53 erratum #843419, the GCC toolchain
> +            // may convert an ADRP instruction at the end of a page (0xffc
> +            // offset) into an ADR instruction. If so, be sure to calculate the
> +            // offset for an ADR instead of ADRP.
> +            //
> +            if ((*(UINT32 *)Targ & BIT31) == 0) {
> +              //
> +              // Calculate the offset for an ADR.
> +              //
> +              Offset = (Sym->st_value & ~0xfff) - Rel->r_offset;
> +              if (Offset < -0x100000 || Offset > 0xfffff) {
> +                Error (NULL, 0, 3000, "Invalid", "WriteSections64(): %s  due to its size (> 1 MB), unable to relocate ADR.",
> +                  mInImageName);
> +                break;
> +              }
> +            } else {
> +              //
> +              // Calculate the offset for an ADRP.
> +              //
> +              Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
> +            }
>   
>               *(UINT32 *)Targ &= 0x9000001f;
>               *(UINT32 *)Targ |= ((Offset & 0x1ffffc) << (5 - 2)) | ((Offset & 0x3) << 29);




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Re: [edk2-devel] [PATCH v2] BaseTools/GenFw: Correct offset when relocating an ADR

[Ard Biesheuvel]

On Wed, 20 Dec 2023 at 22:26, Rebecca Cran <rebecca@bsdio.com> wrote:
>
> Reviewed-by: Rebecca Cran <rebecca@bsdio.com>
>

Merged as #5183

Thanks all

>
> On 12/20/2023 12:31 PM, Jake Garver wrote:
> > In the R_AARCH64_ADR_GOT_PAGE case on AARCH64, we may encounter an ADR
> > instead of an ADRP when the toolchain is working around Cortex-A53
> > erratum #843419.  If that's the case, be sure to calculate the offset
> > appropriately.
> >
> > This resolves an issue experienced when building a StandaloneMm image
> > with stack protection enabled on GCC compiled with
> > "--enable-fix-cortex-a53-843419".  This scenario sometimes generates an
> > ADR with a R_AARCH64_ADR_GOT_PAGE relocation.
> >
> > In this scenario, the following code is being generated by the
> > toolchain:
> >
> >      # Load to set the stack canary
> >      2ffc:    10028020        adr     x0, 8000 <mErrorString+0x1bc>
> >      3008:    f940d400        ldr     x0, [x0, #424]
> >
> >      # Load to check the stack canary
> >      30cc:    b0000020        adrp    x0, 8000 <mErrorString+0x1bc>
> >      30d0:    f940d400        ldr     x0, [x0, #424]
> >
> > GenFw rewrote that to:
> >
> >      # Load to set the stack canary
> >      2ffc:    10000480        adr     x0, 0x308c
> >      3008:    912ec000        add     x0, x0, #0xbb0
> >
> >      # Load to check the stack canary
> >      30cc:    f0000460        adrp    x0, 0x92000
> >      30d0:    912ec000        add     x0, x0, #0xbb0
> >
> > Note that we're now setting the stack canary from the wrong address,
> > resulting in an erroneous stack fault.
> >
> > After this fix, the offset will be calculated correctly for an ADR and
> > the stack canary is set correctly.
> >
> > Signed-off-by: Jake Garver <jake@nvidia.com>
> > ---
> >
> > Notes:
> >    v2: Implement approach proposed by Ard Biesheuvel.
> >      - title changed to: Correct offset when relocating an ADR
> >    v1: Original title: Change opcode when converting ADR to ADRP
> >
> >   BaseTools/Source/C/GenFw/Elf64Convert.c | 22 +++++++++++++++++++++-
> >   1 file changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c b/BaseTools/Source/C/GenFw/Elf64Convert.c
> > index 9911db65af..9d04fc612e 100644
> > --- a/BaseTools/Source/C/GenFw/Elf64Convert.c
> > +++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
> > @@ -1562,7 +1562,27 @@ WriteSections64 (
> >               // subsequent LDR instruction (covered by a R_AARCH64_LD64_GOT_LO12_NC
> >               // relocation) into an ADD instruction - this is handled above.
> >               //
> > -            Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
> > +            // In order to handle Cortex-A53 erratum #843419, the GCC toolchain
> > +            // may convert an ADRP instruction at the end of a page (0xffc
> > +            // offset) into an ADR instruction. If so, be sure to calculate the
> > +            // offset for an ADR instead of ADRP.
> > +            //
> > +            if ((*(UINT32 *)Targ & BIT31) == 0) {
> > +              //
> > +              // Calculate the offset for an ADR.
> > +              //
> > +              Offset = (Sym->st_value & ~0xfff) - Rel->r_offset;
> > +              if (Offset < -0x100000 || Offset > 0xfffff) {
> > +                Error (NULL, 0, 3000, "Invalid", "WriteSections64(): %s  due to its size (> 1 MB), unable to relocate ADR.",
> > +                  mInImageName);
> > +                break;
> > +              }
> > +            } else {
> > +              //
> > +              // Calculate the offset for an ADRP.
> > +              //
> > +              Offset = (Sym->st_value - (Rel->r_offset & ~0xfff)) >> 12;
> > +            }
> >
> >               *(UINT32 *)Targ &= 0x9000001f;
> >               *(UINT32 *)Targ |= ((Offset & 0x1ffffc) << (5 - 2)) | ((Offset & 0x3) << 29);
>
>
>
>
> 
>
>


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