diff options
Diffstat (limited to 'toolchain/elf2flt/patches/v2021.08/0002-elf2flt.ld-reinstate-32-byte-alignment-for-.data-sec.patch')
| -rw-r--r-- | toolchain/elf2flt/patches/v2021.08/0002-elf2flt.ld-reinstate-32-byte-alignment-for-.data-sec.patch | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/toolchain/elf2flt/patches/v2021.08/0002-elf2flt.ld-reinstate-32-byte-alignment-for-.data-sec.patch b/toolchain/elf2flt/patches/v2021.08/0002-elf2flt.ld-reinstate-32-byte-alignment-for-.data-sec.patch new file mode 100644 index 000000000..4df3ea592 --- /dev/null +++ b/toolchain/elf2flt/patches/v2021.08/0002-elf2flt.ld-reinstate-32-byte-alignment-for-.data-sec.patch @@ -0,0 +1,81 @@ +From 85ba5664eb368eb1cbd2c30b7cd574acd75edd4c Mon Sep 17 00:00:00 2001 +From: Niklas Cassel <niklas.cassel@wdc.com> +Date: Mon, 4 Apr 2022 15:30:24 +0200 +Subject: [PATCH] elf2flt.ld: reinstate 32 byte alignment for .data section + +Commit 8a3e74446fe7 ("allow to build arm flat binaries") moved the +following commands: + . = ALIGN(0x20) ; + @SYMBOL_PREFIX@_etext = . ; +from the .text section to the top level in the SECTIONS node. + +The .text output section is being directed to a memory region using the +"> flatmem :text" output section attribute. Commands in the top level in +the SECTIONS node are not. + +This means that the ALIGN() command is no longer being appended to the +flatmem memory region, it will simply update the Location Counter. + +The heuristic for placing an output section is described here: +https://sourceware.org/binutils/docs-2.38/ld.html#Output-Section-Address + +"If an output memory region is set for the section then it is added to this +region and its address will be the next free address in that region." + +Since the .data section is being directed to the same memory region as the +.text section, this means that the Location Counter is not used when +assigning an address to the .data output section, it will simply use the +next free address. + +No longer directing these commands to the flatmem memory region means that +the .data output section is no longer aligned to a 32 byte boundary. + +Before commit 8a3e74446fe7 ("allow to build arm flat binaries"): +$ readelf -S busybox_unstripped.gdb | grep data + [ 3] .data PROGBITS 0000000000035ac0 00036ac0 +$ readelf -s busybox_unstripped.gdb | grep _etext + 19286: 0000000000035ac0 0 NOTYPE GLOBAL DEFAULT 1 _etext + +After commit 8a3e74446fe7 ("allow to build arm flat binaries"): +$ readelf -S busybox_unstripped.gdb | grep data + [ 3] .data PROGBITS 0000000000035ab0 00036ab0 +$ readelf -s busybox_unstripped.gdb | grep _etext + 19287: 0000000000035ac0 0 NOTYPE GLOBAL DEFAULT 3 _etext + +The .data output section has to be aligned to a 32 byte boundary, see the +FLAT_DATA_ALIGN 0x20 macro and its usage in fs/binfmt_flat.c: +https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/binfmt_flat.c?h=v5.17#n59 + +Readd an explicit ALIGN attribute on the .data section itself, since the +linker will obey this attribute regardless if being directed to a memory +region or not. Also remove the ALIGN() command before the .data section, +since this misleads the reader to think that the Location Counter is used +when assigning an address to the .data section, when it actually is not. + +Fixes: 8a3e74446fe7 ("allow to build arm flat binaries") +Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com> +--- + elf2flt.ld.in | 5 +---- + 1 file changed, 1 insertion(+), 4 deletions(-) + +diff --git a/elf2flt.ld.in b/elf2flt.ld.in +index 0df999d..e5aea14 100644 +--- a/elf2flt.ld.in ++++ b/elf2flt.ld.in +@@ -94,12 +94,9 @@ W_RODAT: *(.gnu.linkonce.r*) + *(.ARM.exidx* .gnu.linkonce.armexidx.*) + } > flatmem + @SYMBOL_PREFIX@__exidx_end = .; +- +- . = ALIGN(0x20) ; + @SYMBOL_PREFIX@_etext = . ; + +- .data : { +- . = ALIGN(0x4) ; ++ .data ALIGN(0x20): { + @SYMBOL_PREFIX@_sdata = . ; + @SYMBOL_PREFIX@__data_start = . ; + @SYMBOL_PREFIX@data_start = . ; +-- +2.35.1 + |