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target/riscv: tracking indirect branches (fcfi) for zicfilp

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zicfilp protects forward control flow (if enabled) by enforcing all
indirect call and jmp must land on a landing pad instruction `lpad`. If
target of an indirect call or jmp is not `lpad` then cpu/hart must raise
a sw check exception with tval = 2.

This patch implements the mechanism using TCG. Target architecture branch
instruction must define the end of a TB. Using this property, during
translation of branch instruction, TB flag = FCFI_LP_EXPECTED can be set.
Translation of target TB can check if FCFI_LP_EXPECTED flag is set and a
flag (fcfi_lp_expected) can be set in DisasContext. If `lpad` gets
translated, fcfi_lp_expected flag in DisasContext can be cleared. Else
it'll fault.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Co-developed-by: Jim Shu <jim.shu@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241008225010.1861630-7-debug@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Deepak Gupta 2024-10-08 15:49:56 -07:00 • committed by Alistair Francis
parent 6031102401
commit b039c96113
4 changed files with 39 additions and 0 deletions
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10
target/riscv/cpu_helper.c
View file

@ -132,6 +132,16 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
flags = FIELD_DP32(flags, TB_FLAGS, VILL, 1);
}
if (cpu_get_fcfien(env)) {
/*
* For Forward CFI, only the expectation of a lpad at
* the start of the block is tracked via env->elp. env->elp
* is turned on during jalr translation.
*/
flags = FIELD_DP32(flags, TB_FLAGS, FCFI_LP_EXPECTED, env->elp);
flags = FIELD_DP32(flags, TB_FLAGS, FCFI_ENABLED, 1);
}
#ifdef CONFIG_USER_ONLY
fs = EXT_STATUS_DIRTY;
vs = EXT_STATUS_DIRTY;