mirror of https://github.com/acidanthera/audk.git
5d533bbc27
When converting ELF to PE/COFF for the AArch64 target, we may encounter an R_AARCH64_ADR_GOT_PAGE relocation that refers to an ADR instruction instead of an ADRP instruction. This can happen 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 (which is built with -fpie) with stack protection enabled on GCC compiled with "--enable-fix-cortex-a53-843419". In this case, the linker may convert an ADRP instruction appearing at an offset of 0xff8 or 0xffc modulo 4KiB into an ADR instruction, but will leave the original R_AARCH64_ADR_GOT_PAGE relocation in place. (This is not a bug in the linker, given that there is no other relocation type that it could reasonably convert it into) 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. Note that there is a corner case where this may cause the conversion to fail: if the original GOT entry is just within -/+ 1 MiB of the reference, but the actual variable it refers to is not, the resulting offset cannot be represented by the immediate offset field in a ADR instruction. Given that this issue only affects PIE executables, which are rare and usually tiny, this is unlikely to cause problems in practice. Ref: https://edk2.groups.io/g/devel/topic/102202314 [ardb: expand commit log, add reference] Signed-off-by: Jake Garver <jake@nvidia.com> Reviewed-by: Rebecca Cran <rebecca@bsdio.com> |
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