On Wed, 09 Feb 2022 04:37:53 PST (-0800), heiko@xxxxxxxxx wrote:
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.
There should probably be a ".option norelax" in here as well, as relaxation will trigger exactly the same issues. That, or we could just remove the constraint that these must be the same size (ie, automatically pad the smaller one with NOP/jump-to-end).
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@xxxxxxxxx> --- arch/riscv/include/asm/alternative-macros.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h index c0fb11fad631..3a52884bf23d 100644 --- a/arch/riscv/include/asm/alternative-macros.h +++ b/arch/riscv/include/asm/alternative-macros.h @@ -19,7 +19,10 @@ .popsection .subsection 1 888 : + .option push + .option norvc \new_c + .option pop 889 : .previous .org . - (889b - 888b) + (887b - 886b) @@ -29,7 +32,10 @@ .macro __ALTERNATIVE_CFG old_c, new_c, vendor_id, errata_id, enable 886 : + .option push + .option norvc \old_c + .option pop 887 : ALT_NEW_CONTENT \vendor_id, \errata_id, \enable, \new_c .endm @@ -40,7 +46,10 @@ .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 \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 @@ -70,7 +79,10 @@ ".popsection\n" \ ".subsection 1\n" \ "888 :\n" \ + ".option push\n" \ + ".option norvc\n" \ new_c "\n" \ + ".option pop\n" \ "889 :\n" \ ".previous\n" \ ".org . - (887b - 886b) + (889b - 888b)\n" \ @@ -79,7 +91,10 @@ #define __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, enable) \ "886 :\n" \ + ".option push\n" \ + ".option norvc\n" \ old_c "\n" \ + ".option pop\n" \ "887 :\n" \ ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c) @@ -89,7 +104,10 @@ #define __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 :\n" \ + ".option push\n" \ + ".option norvc\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)
