From 20b6643324a79860dcdfe811ffe4a79942bca21e Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 5 Dec 2022 17:45:02 -0600 Subject: [PATCH] tcg/ppc: Reorg goto_tb implementation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The old ppc64 implementation replaces 2 or 4 insns, which leaves a race condition in which a thread could be stopped at a PC in the middle of the sequence, and when restarted does not see the complete address computation and branches to nowhere. The new implemetation replaces only one insn, swapping between b and mtctr r31 falling through to a general-case indirect branch. Reviewed-by: Alex Bennée Signed-off-by: Richard Henderson --- tcg/ppc/tcg-target.c.inc | 158 +++++++++++---------------------------- tcg/ppc/tcg-target.h | 3 +- 2 files changed, 44 insertions(+), 117 deletions(-) diff --git a/tcg/ppc/tcg-target.c.inc b/tcg/ppc/tcg-target.c.inc index 6f2c8faea6..8d6899cf40 100644 --- a/tcg/ppc/tcg-target.c.inc +++ b/tcg/ppc/tcg-target.c.inc @@ -1854,104 +1854,6 @@ static void tcg_out_mb(TCGContext *s, TCGArg a0) tcg_out32(s, insn); } -static inline uint64_t make_pair(tcg_insn_unit i1, tcg_insn_unit i2) -{ - if (HOST_BIG_ENDIAN) { - return (uint64_t)i1 << 32 | i2; - } - return (uint64_t)i2 << 32 | i1; -} - -static inline void ppc64_replace2(uintptr_t rx, uintptr_t rw, - tcg_insn_unit i0, tcg_insn_unit i1) -{ -#if TCG_TARGET_REG_BITS == 64 - qatomic_set((uint64_t *)rw, make_pair(i0, i1)); - flush_idcache_range(rx, rw, 8); -#else - qemu_build_not_reached(); -#endif -} - -static inline void ppc64_replace4(uintptr_t rx, uintptr_t rw, - tcg_insn_unit i0, tcg_insn_unit i1, - tcg_insn_unit i2, tcg_insn_unit i3) -{ - uint64_t p[2]; - - p[!HOST_BIG_ENDIAN] = make_pair(i0, i1); - p[HOST_BIG_ENDIAN] = make_pair(i2, i3); - - /* - * There's no convenient way to get the compiler to allocate a pair - * of registers at an even index, so copy into r6/r7 and clobber. - */ - asm("mr %%r6, %1\n\t" - "mr %%r7, %2\n\t" - "stq %%r6, %0" - : "=Q"(*(__int128 *)rw) : "r"(p[0]), "r"(p[1]) : "r6", "r7"); - flush_idcache_range(rx, rw, 16); -} - -void tb_target_set_jmp_target(const TranslationBlock *tb, int n, - uintptr_t jmp_rx, uintptr_t jmp_rw) -{ - tcg_insn_unit i0, i1, i2, i3; - uintptr_t addr = tb->jmp_target_addr[n]; - intptr_t tb_diff = addr - (uintptr_t)tb->tc.ptr; - intptr_t br_diff = addr - (jmp_rx + 4); - intptr_t lo, hi; - - if (TCG_TARGET_REG_BITS == 32) { - intptr_t diff = addr - jmp_rx; - tcg_debug_assert(in_range_b(diff)); - qatomic_set((uint32_t *)jmp_rw, B | (diff & 0x3fffffc)); - flush_idcache_range(jmp_rx, jmp_rw, 4); - return; - } - - /* - * For 16-bit displacements, we can use a single add + branch. - * This happens quite often. - */ - if (tb_diff == (int16_t)tb_diff) { - i0 = ADDI | TAI(TCG_REG_TB, TCG_REG_TB, tb_diff); - i1 = B | (br_diff & 0x3fffffc); - ppc64_replace2(jmp_rx, jmp_rw, i0, i1); - return; - } - - lo = (int16_t)tb_diff; - hi = (int32_t)(tb_diff - lo); - assert(tb_diff == hi + lo); - i0 = ADDIS | TAI(TCG_REG_TB, TCG_REG_TB, hi >> 16); - i1 = ADDI | TAI(TCG_REG_TB, TCG_REG_TB, lo); - - /* - * Without stq from 2.07, we can only update two insns, - * and those must be the ones that load the target address. - */ - if (!have_isa_2_07) { - ppc64_replace2(jmp_rx, jmp_rw, i0, i1); - return; - } - - /* - * For 26-bit displacements, we can use a direct branch. - * Otherwise we still need the indirect branch, which we - * must restore after a potential direct branch write. - */ - br_diff -= 4; - if (in_range_b(br_diff)) { - i2 = B | (br_diff & 0x3fffffc); - i3 = NOP; - } else { - i2 = MTSPR | RS(TCG_REG_TB) | CTR; - i3 = BCCTR | BO_ALWAYS; - } - ppc64_replace4(jmp_rx, jmp_rw, i0, i1, i2, i3); -} - static void tcg_out_call_int(TCGContext *s, int lk, const tcg_insn_unit *target) { @@ -2625,30 +2527,56 @@ static void tcg_out_exit_tb(TCGContext *s, uintptr_t arg) static void tcg_out_goto_tb(TCGContext *s, int which) { - /* Direct jump. */ - if (TCG_TARGET_REG_BITS == 64) { - /* Ensure the next insns are 8 or 16-byte aligned. */ - while ((uintptr_t)s->code_ptr & (have_isa_2_07 ? 15 : 7)) { - tcg_out32(s, NOP); - } + uintptr_t ptr = get_jmp_target_addr(s, which); + + if (USE_REG_TB) { + ptrdiff_t offset = tcg_tbrel_diff(s, (void *)ptr); + tcg_out_mem_long(s, LD, LDX, TCG_REG_TB, TCG_REG_TB, offset); + + /* Direct branch will be patched by tb_target_set_jmp_target. */ set_jmp_insn_offset(s, which); - tcg_out32(s, ADDIS | TAI(TCG_REG_TB, TCG_REG_TB, 0)); - tcg_out32(s, ADDI | TAI(TCG_REG_TB, TCG_REG_TB, 0)); tcg_out32(s, MTSPR | RS(TCG_REG_TB) | CTR); + + /* When branch is out of range, fall through to indirect. */ + tcg_out32(s, BCCTR | BO_ALWAYS); + + /* For the unlinked case, need to reset TCG_REG_TB. */ + set_jmp_reset_offset(s, which); + tcg_out_mem_long(s, ADDI, ADD, TCG_REG_TB, TCG_REG_TB, + -tcg_current_code_size(s)); + } else { + /* Direct branch will be patched by tb_target_set_jmp_target. */ + set_jmp_insn_offset(s, which); + tcg_out32(s, NOP); + + /* When branch is out of range, fall through to indirect. */ + tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_TMP1, ptr - (int16_t)ptr); + tcg_out_ld(s, TCG_TYPE_PTR, TCG_REG_TMP1, TCG_REG_TMP1, (int16_t)ptr); + tcg_out32(s, MTSPR | RS(TCG_REG_TMP1) | CTR); tcg_out32(s, BCCTR | BO_ALWAYS); set_jmp_reset_offset(s, which); - if (USE_REG_TB) { - /* For the unlinked case, need to reset TCG_REG_TB. */ - tcg_out_mem_long(s, ADDI, ADD, TCG_REG_TB, TCG_REG_TB, - -tcg_current_code_size(s)); - } - } else { - set_jmp_insn_offset(s, which); - tcg_out32(s, B); - set_jmp_reset_offset(s, which); } } +void tb_target_set_jmp_target(const TranslationBlock *tb, int n, + uintptr_t jmp_rx, uintptr_t jmp_rw) +{ + uintptr_t addr = tb->jmp_target_addr[n]; + intptr_t diff = addr - jmp_rx; + tcg_insn_unit insn; + + if (in_range_b(diff)) { + insn = B | (diff & 0x3fffffc); + } else if (USE_REG_TB) { + insn = MTSPR | RS(TCG_REG_TB) | CTR; + } else { + insn = NOP; + } + + qatomic_set((uint32_t *)jmp_rw, insn); + flush_idcache_range(jmp_rx, jmp_rw, 4); +} + static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg args[TCG_MAX_OP_ARGS], const int const_args[TCG_MAX_OP_ARGS]) diff --git a/tcg/ppc/tcg-target.h b/tcg/ppc/tcg-target.h index f253184915..af81c5a57f 100644 --- a/tcg/ppc/tcg-target.h +++ b/tcg/ppc/tcg-target.h @@ -27,11 +27,10 @@ #ifdef _ARCH_PPC64 # define TCG_TARGET_REG_BITS 64 -# define MAX_CODE_GEN_BUFFER_SIZE (2 * GiB) #else # define TCG_TARGET_REG_BITS 32 -# define MAX_CODE_GEN_BUFFER_SIZE (32 * MiB) #endif +#define MAX_CODE_GEN_BUFFER_SIZE ((size_t)-1) #define TCG_TARGET_NB_REGS 64 #define TCG_TARGET_INSN_UNIT_SIZE 4