Exact

Exact Union RegExp

Mateusz Jończyk 42a39e4aa5 mips/math-emu: fix emulation of the prefx instruction ... Currently, installation of Debian 12.8 for mipsel fails on machines without an FPU [1]. This is caused by the fact that zstd (which is used for initramfs compression) executes the prefx instruction, which is not emulated properly by the kernel. The prefx (Prefetch Indexed) instruction fetches data from memory into the cache without any side effects. Though functionally unrelated, it requires an FPU [2]. Bytecode format of this instruction ends on "001111" binary: (prefx instruction format) & 0x0000003f = 0x0000000f The code in fpux_emu() runs like so: #define MIPSInst(x) x #define MIPSInst_FMA_FFMT(x) (MIPSInst(x) & 0x00000007) #define MIPSInst_FUNC(x) (MIPSInst(x) & 0x0000003f) enum cop1x_func { ..., pfetch_op = 0x0f, ... }; ... switch (MIPSInst_FMA_FFMT(ir)) { ... case 0x3: if (MIPSInst_FUNC(ir) != pfetch_op) return SIGILL; /* ignore prefx operation */ break; default: return SIGILL; } That snippet above contains a logic error and the if (MIPSInst_FUNC(ir) != pfetch_op) comparison always fires. When MIPSInst_FUNC(ir) is equal to pfetch_op, ir must end on 001111 binary. In this case, MIPSInst_FMA_FFMT(ir) must be equal to 0x7, which does not match that case label. This causes emulation failure for the prefx instruction. Fix it. This has been broken by commit 919af8b96c ("MIPS: Make definitions of MIPSInst_FMA_{FUNC,FMTM} consistent with MIPS64 manual") which modified the MIPSInst_FMA_FFMT macro without updating the users. Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl> Cc: stable@vger.kernel.org # after 3 weeks Cc: Dengcheng Zhu <dzhu@wavecomp.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Ming Wang <wangming01@loongson.cn> Cc: Tiezhu Yang <yangtiezhu@loongson.cn> Fixes: 919af8b96c ("MIPS: Make definitions of MIPSInst_FMA_{FUNC,FMTM} consistent with MIPS64 manual") [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1091858 [2] MIPS Architecture For Programmers Volume II-A: The MIPS32 Instruction Set Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>		2025-01-11 12:49:05 +01:00
..
cp1emu.c
dp_2008class.c
dp_add.c
dp_cmp.c
dp_div.c
dp_fint.c
dp_flong.c
dp_fmax.c
dp_fmin.c
dp_fsp.c
dp_maddf.c
dp_mul.c
dp_rint.c
dp_simple.c
dp_sqrt.c
dp_sub.c
dp_tint.c
dp_tlong.c
dsemul.c
ieee754.c
ieee754.h
ieee754d.c
ieee754dp.c
ieee754dp.h
ieee754int.h
ieee754sp.c
ieee754sp.h
Makefile
me-debugfs.c
sp_2008class.c
sp_add.c
sp_cmp.c
sp_div.c
sp_fdp.c
sp_fint.c
sp_flong.c
sp_fmax.c
sp_fmin.c
sp_maddf.c
sp_mul.c
sp_rint.c
sp_simple.c
sp_sqrt.c
sp_sub.c
sp_tint.c
sp_tlong.c