From c80ee64a8020ef1a6a92109798080786829b8994 Mon Sep 17 00:00:00 2001 From: Jisheng Zhang Date: Fri, 11 Feb 2022 00:49:43 +0800 Subject: [PATCH 1/2] riscv: alternative only works on !XIP_KERNEL The alternative mechanism needs runtime code patching, it can't work on XIP_KERNEL. And the errata workarounds are implemented via the alternative mechanism. So add !XIP_KERNEL dependency for alternative and erratas. Signed-off-by: Jisheng Zhang Fixes: 44c922572952 ("RISC-V: enable XIP") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt --- arch/riscv/Kconfig.erratas | 1 + arch/riscv/Kconfig.socs | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas index b44d6ecdb46e..0aacd7052585 100644 --- a/arch/riscv/Kconfig.erratas +++ b/arch/riscv/Kconfig.erratas @@ -2,6 +2,7 @@ menu "CPU errata selection" config RISCV_ERRATA_ALTERNATIVE bool "RISC-V alternative scheme" + depends on !XIP_KERNEL default y help This Kconfig allows the kernel to automatically patch the diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs index 6ec44a22278a..c112ab2a9052 100644 --- a/arch/riscv/Kconfig.socs +++ b/arch/riscv/Kconfig.socs @@ -14,8 +14,8 @@ config SOC_SIFIVE select CLK_SIFIVE select CLK_SIFIVE_PRCI select SIFIVE_PLIC - select RISCV_ERRATA_ALTERNATIVE - select ERRATA_SIFIVE + select RISCV_ERRATA_ALTERNATIVE if !XIP_KERNEL + select ERRATA_SIFIVE if !XIP_KERNEL help This enables support for SiFive SoC platform hardware. From 0966d385830de3470b7131db8e86c0c5bc9c52dc Mon Sep 17 00:00:00 2001 From: Emil Renner Berthing Date: Wed, 23 Feb 2022 20:12:57 +0100 Subject: [PATCH 2/2] riscv: Fix auipc+jalr relocation range checks RISC-V can do PC-relative jumps with a 32bit range using the following two instructions: auipc t0, imm20 ; t0 = PC + imm20 * 2^12 jalr ra, t0, imm12 ; ra = PC + 4, PC = t0 + imm12 Crucially both the 20bit immediate imm20 and the 12bit immediate imm12 are treated as two's-complement signed values. For this reason the immediates are usually calculated like this: imm20 = (offset + 0x800) >> 12 imm12 = offset & 0xfff ..where offset is the signed offset from the auipc instruction. When the 11th bit of offset is 0 the addition of 0x800 doesn't change the top 20 bits and imm12 considered positive. When the 11th bit is 1 the carry of the addition by 0x800 means imm20 is one higher, but since imm12 is then considered negative the two's complement representation means it all cancels out nicely. However, this addition by 0x800 (2^11) means an offset greater than or equal to 2^31 - 2^11 would overflow so imm20 is considered negative and result in a backwards jump. Similarly the lower range of offset is also moved down by 2^11 and hence the true 32bit range is [-2^31 - 2^11, 2^31 - 2^11) Signed-off-by: Emil Renner Berthing Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/module.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c index 68a9e3d1fe16..4a48287513c3 100644 --- a/arch/riscv/kernel/module.c +++ b/arch/riscv/kernel/module.c @@ -13,6 +13,19 @@ #include #include +/* + * The auipc+jalr instruction pair can reach any PC-relative offset + * in the range [-2^31 - 2^11, 2^31 - 2^11) + */ +static bool riscv_insn_valid_32bit_offset(ptrdiff_t val) +{ +#ifdef CONFIG_32BIT + return true; +#else + return (-(1L << 31) - (1L << 11)) <= val && val < ((1L << 31) - (1L << 11)); +#endif +} + static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v) { if (v != (u32)v) { @@ -95,7 +108,7 @@ static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location, ptrdiff_t offset = (void *)v - (void *)location; s32 hi20; - if (offset != (s32)offset) { + if (!riscv_insn_valid_32bit_offset(offset)) { pr_err( "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n", me->name, (long long)v, location); @@ -197,10 +210,9 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location, Elf_Addr v) { ptrdiff_t offset = (void *)v - (void *)location; - s32 fill_v = offset; u32 hi20, lo12; - if (offset != fill_v) { + if (!riscv_insn_valid_32bit_offset(offset)) { /* Only emit the plt entry if offset over 32-bit range */ if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) { offset = module_emit_plt_entry(me, v); @@ -224,10 +236,9 @@ static int apply_r_riscv_call_rela(struct module *me, u32 *location, Elf_Addr v) { ptrdiff_t offset = (void *)v - (void *)location; - s32 fill_v = offset; u32 hi20, lo12; - if (offset != fill_v) { + if (!riscv_insn_valid_32bit_offset(offset)) { pr_err( "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n", me->name, (long long)v, location);