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| author | Heiko Stuebner <heiko@sntech.de> | 2022-05-11 22:29:15 +0300 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-05-12 07:36:32 +0300 |
| commit | 49b290e430d390bacf7d3792d5654fa4b3212926 (patch) | |
| tree | 39e1bb6c10655454e9f57c16bfc503af2f0c99a4 /arch/riscv/include | |
| parent | e509204acb03785719cda632758b7ac6cd351e28 (diff) | |
| download | linux-49b290e430d390bacf7d3792d5654fa4b3212926.tar.xz | |
riscv: prevent compressed instructions in alternatives
Instructions are opportunistically compressed by the RISC-V assembler
when possible, but in alternatives-blocks both the old and new content
need to be the same size, so having the toolchain do somewhat random
optimizations will cause strange side-effects like
"attempt to move .org backwards" compile-time errors.
Already a simple "and" used in alternatives assembly will cause these
mismatched code sizes.
So prevent compressed instructions to be generated in alternatives-
code and use option-push and -pop to only limit this to the relevant
code blocks
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-7-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/include')
| -rw-r--r-- | arch/riscv/include/asm/alternative-macros.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h index 8c2bbc7bbe50..e13b1f6bb400 100644 --- a/arch/riscv/include/asm/alternative-macros.h +++ b/arch/riscv/include/asm/alternative-macros.h @@ -21,7 +21,11 @@ .popsection .subsection 1 888 : + .option push + .option norvc + .option norelax \new_c + .option pop 889 : .previous .org . - (889b - 888b) + (887b - 886b) @@ -31,7 +35,11 @@ .macro __ALTERNATIVE_CFG old_c, new_c, vendor_id, errata_id, enable 886 : + .option push + .option norvc + .option norelax \old_c + .option pop 887 : ALT_NEW_CONTENT \vendor_id, \errata_id, \enable, \new_c .endm @@ -42,7 +50,11 @@ .macro __ALTERNATIVE_CFG_2 old_c, new_c_1, vendor_id_1, errata_id_1, enable_1, \ new_c_2, vendor_id_2, errata_id_2, enable_2 886 : + .option push + .option norvc + .option norelax \old_c + .option pop 887 : ALT_NEW_CONTENT \vendor_id_1, \errata_id_1, \enable_1, \new_c_1 ALT_NEW_CONTENT \vendor_id_2, \errata_id_2, \enable_2, \new_c_2 @@ -76,7 +88,11 @@ ".popsection\n" \ ".subsection 1\n" \ "888 :\n" \ + ".option push\n" \ + ".option norvc\n" \ + ".option norelax\n" \ new_c "\n" \ + ".option pop\n" \ "889 :\n" \ ".previous\n" \ ".org . - (887b - 886b) + (889b - 888b)\n" \ @@ -85,7 +101,11 @@ #define __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, enable) \ "886 :\n" \ + ".option push\n" \ + ".option norvc\n" \ + ".option norelax\n" \ old_c "\n" \ + ".option pop\n" \ "887 :\n" \ ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c) @@ -97,7 +117,11 @@ new_c_2, vendor_id_2, errata_id_2, \ enable_2) \ "886 :\n" \ + ".option push\n" \ + ".option norvc\n" \ + ".option norelax\n" \ old_c "\n" \ + ".option pop\n" \ "887 :\n" \ ALT_NEW_CONTENT(vendor_id_1, errata_id_1, enable_1, new_c_1) \ ALT_NEW_CONTENT(vendor_id_2, errata_id_2, enable_2, new_c_2) |