From 923976dfe367b0bfed45ff660c369f3fe65604a7 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Sat, 17 May 2025 13:12:07 +0200 Subject: [PATCH 1/3] target/hppa: Copy instruction code into fr1 on FPU assist fault The hardware stores the instruction code in the lower bits of the FP exception register #1 on FP assist traps. This fixes the FP exception handler on Linux, as the Linux kernel uses the value to decide on the correct signal which should be pushed into userspace (see decode_fpu() in Linux kernel). Signed-off-by: Helge Deller --- target/hppa/int_helper.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/target/hppa/int_helper.c b/target/hppa/int_helper.c index 7d48643bb6..191ae19404 100644 --- a/target/hppa/int_helper.c +++ b/target/hppa/int_helper.c @@ -177,6 +177,10 @@ void hppa_cpu_do_interrupt(CPUState *cs) } } env->cr[CR_IIR] = ldl_phys(cs->as, paddr); + if (i == EXCP_ASSIST) { + /* stuff insn code into bits of FP exception register #1 */ + env->fr[0] |= (env->cr[CR_IIR] & 0x03ffffff); + } } break; From b4b49cf39dba5f993ad925f204cb820aacfc8e45 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Sat, 17 May 2025 13:20:17 +0200 Subject: [PATCH 2/3] linux-user/hppa: Send proper si_code on SIGFPE exception Improve the linux-user emulation to send the correct si_code depending on overflow (TARGET_FPE_FLTOVF), underflow (TARGET_FPE_FLTUND), ... Note that the hardware stores the relevant flags in FP exception register #1, which is actually the lower 32-bits of the 64-bit fr[0] register in qemu. Signed-off-by: Helge Deller --- linux-user/hppa/cpu_loop.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/linux-user/hppa/cpu_loop.c b/linux-user/hppa/cpu_loop.c index 890e758cd1..9abaad5ef8 100644 --- a/linux-user/hppa/cpu_loop.c +++ b/linux-user/hppa/cpu_loop.c @@ -112,7 +112,7 @@ static abi_ulong hppa_lws(CPUHPPAState *env) void cpu_loop(CPUHPPAState *env) { CPUState *cs = env_cpu(env); - abi_ulong ret; + abi_ulong ret, si_code = 0; int trapnr; while (1) { @@ -169,7 +169,15 @@ void cpu_loop(CPUHPPAState *env) force_sig_fault(TARGET_SIGFPE, TARGET_FPE_CONDTRAP, env->iaoq_f); break; case EXCP_ASSIST: - force_sig_fault(TARGET_SIGFPE, 0, env->iaoq_f); + #define set_si_code(mask, val) \ + if (env->fr[0] & mask) { si_code = val; } + set_si_code(R_FPSR_FLG_I_MASK, TARGET_FPE_FLTRES); + set_si_code(R_FPSR_FLG_U_MASK, TARGET_FPE_FLTUND); + set_si_code(R_FPSR_FLG_O_MASK, TARGET_FPE_FLTOVF); + set_si_code(R_FPSR_FLG_Z_MASK, TARGET_FPE_FLTDIV); + set_si_code(R_FPSR_FLG_V_MASK, TARGET_FPE_FLTINV); + #undef set_si_code + force_sig_fault(TARGET_SIGFPE, si_code, env->iaoq_f); break; case EXCP_BREAK: force_sig_fault(TARGET_SIGTRAP, TARGET_TRAP_BRKPT, env->iaoq_f); From ebd394948de4e868cb8fc5b265a8a18f0935dce1 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Sat, 17 May 2025 13:27:48 +0200 Subject: [PATCH 3/3] target/hppa: Fix FPE exceptions Implement FP exception register #1 (lower 32-bits of 64-bit fr[0]). A proper implementation is necessary to allow the Linux kernel in system mode and the qemu linux-user to send proper si_code values on SIGFPE signal. Always set the T-bit on taken exception, and merge over- and underflow in system mode to just set overflow bit to mimic the behaviour I tested on a physical machine. The test program below can be used to verify correct behaviour. Note that behaviour on SIGFPE may vary on different platforms. The program should always detect the correct signal, but it may or may not be able to sucessfully continue afterwards. #define _GNU_SOURCE #include #include #include #include static void fpe_func(int sig, siginfo_t *i, void *v) { sigset_t set; sigemptyset(&set); sigaddset(&set, SIGFPE); sigprocmask(SIG_UNBLOCK, &set, NULL); printf("GOT signal %d with si_code %ld\n", sig, i->si_code); } int main(int argc, char *argv[]) { struct sigaction action = { .sa_sigaction = fpe_func, .sa_flags = SA_RESTART|SA_SIGINFO }; sigaction(SIGFPE, &action, 0); feenableexcept(FE_OVERFLOW | FE_UNDERFLOW); double x = DBL_MIN; return printf("%lf\n", argc > 1 ? 1.7976931348623158E308*1.7976931348623158E308 : x / 10); } Signed-off-by: Helge Deller --- target/hppa/fpu_helper.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/target/hppa/fpu_helper.c b/target/hppa/fpu_helper.c index a62d9d3083..294ce0a970 100644 --- a/target/hppa/fpu_helper.c +++ b/target/hppa/fpu_helper.c @@ -95,7 +95,8 @@ static void update_fr0_op(CPUHPPAState *env, uintptr_t ra) { uint32_t soft_exp = get_float_exception_flags(&env->fp_status); uint32_t hard_exp = 0; - uint32_t shadow = env->fr0_shadow; + uint32_t shadow = env->fr0_shadow & 0x3ffffff; + uint32_t fr1 = 0; if (likely(soft_exp == 0)) { env->fr[0] = (uint64_t)shadow << 32; @@ -108,9 +109,22 @@ static void update_fr0_op(CPUHPPAState *env, uintptr_t ra) hard_exp |= CONVERT_BIT(soft_exp, float_flag_overflow, R_FPSR_ENA_O_MASK); hard_exp |= CONVERT_BIT(soft_exp, float_flag_divbyzero, R_FPSR_ENA_Z_MASK); hard_exp |= CONVERT_BIT(soft_exp, float_flag_invalid, R_FPSR_ENA_V_MASK); - shadow |= hard_exp << (R_FPSR_FLAGS_SHIFT - R_FPSR_ENABLES_SHIFT); + if (hard_exp & shadow) { + shadow = FIELD_DP32(shadow, FPSR, T, 1); + /* fill exception register #1, which is lower 32-bits of fr[0] */ +#if !defined(CONFIG_USER_ONLY) + if (hard_exp & (R_FPSR_ENA_O_MASK | R_FPSR_ENA_U_MASK)) { + /* over- and underflow both set overflow flag only */ + fr1 = FIELD_DP32(fr1, FPSR, C, 1); + fr1 = FIELD_DP32(fr1, FPSR, FLG_O, 1); + } else +#endif + { + fr1 |= hard_exp << (R_FPSR_FLAGS_SHIFT - R_FPSR_ENABLES_SHIFT); + } + } env->fr0_shadow = shadow; - env->fr[0] = (uint64_t)shadow << 32; + env->fr[0] = (uint64_t)shadow << 32 | fr1; if (hard_exp & shadow) { hppa_dynamic_excp(env, EXCP_ASSIST, ra);