| Message ID | 20170630004059.25619-3-bobby.prani@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/29/2017 05:40 PM, Pranith Kumar wrote: > void aarch64_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t addr) > { > tcg_insn_unit *code_ptr = (tcg_insn_unit *)jmp_addr; > - tcg_insn_unit *target = (tcg_insn_unit *)addr; > + tcg_insn_unit i1, i2; > + uint64_t pair; > > + ptrdiff_t offset = addr - jmp_addr; > + > + if (offset == sextract64(offset, 0, 26)) { > + i1 = NOP; > + i2 = I3206_B | ((offset >> 2) & 0x3ffffff); Branch first, since that's the offset you calculated. Also, the nop need not be executed. > + } else { > + offset = (addr >> 12) - (jmp_addr >> 12); > + > + /* patch ADRP */ > + i2 = deposit32(*code_ptr++, 29, 2, offset & 0x3); > + i2 = deposit32(i2, 5, 19, offset >> 2); > + /* patch ADDI */ > + i1 = deposit32(*code_ptr, 10, 12, addr & 0xfff); You can't just patch these insns, because they aren't necessarily ADRP+ADD. Indeed, they will very likely be B and NOP. The first address we patch in is tb_jmp_reset_offset, which is the following opcode, which is definitely in range of the branch above. r~
On Fri, Jun 30, 2017 at 12:47 AM, Richard Henderson <rth@twiddle.net> wrote: > On 06/29/2017 05:40 PM, Pranith Kumar wrote: >> >> void aarch64_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t addr) >> { >> tcg_insn_unit *code_ptr = (tcg_insn_unit *)jmp_addr; >> - tcg_insn_unit *target = (tcg_insn_unit *)addr; >> + tcg_insn_unit i1, i2; >> + uint64_t pair; >> + ptrdiff_t offset = addr - jmp_addr; >> + >> + if (offset == sextract64(offset, 0, 26)) { >> + i1 = NOP; >> + i2 = I3206_B | ((offset >> 2) & 0x3ffffff); > > > Branch first, since that's the offset you calculated. > Also, the nop need not be executed. This is exactly how I form the instruction pair below (B+NOP, not NOP+B). But I get your point. It is confusing to use i1 for the second instruction. I'll change it. > >> + } else { >> + offset = (addr >> 12) - (jmp_addr >> 12); >> + >> + /* patch ADRP */ >> + i2 = deposit32(*code_ptr++, 29, 2, offset & 0x3); >> + i2 = deposit32(i2, 5, 19, offset >> 2); >> + /* patch ADDI */ >> + i1 = deposit32(*code_ptr, 10, 12, addr & 0xfff); > > > You can't just patch these insns, because they aren't necessarily ADRP+ADD. > Indeed, they will very likely be B and NOP. The first address we patch in > is tb_jmp_reset_offset, which is the following opcode, which is definitely > in range of the branch above. Whoops, I totally missed that we patch these out the first time out. I will explicitly generate the ADRP+ADD pair from here. Thanks,
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index f6ad46b613..65a92dbf67 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -522,7 +522,7 @@ static inline PageDesc *page_find(tb_page_addr_t index) #elif defined(__powerpc__) # define MAX_CODE_GEN_BUFFER_SIZE (32u * 1024 * 1024) #elif defined(__aarch64__) -# define MAX_CODE_GEN_BUFFER_SIZE (128ul * 1024 * 1024) +# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024) #elif defined(__s390x__) /* We have a +- 4GB range on the branches; leave some slop. */ # define MAX_CODE_GEN_BUFFER_SIZE (3ul * 1024 * 1024 * 1024) diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c index 8fce11ace7..f059d9d781 100644 --- a/tcg/aarch64/tcg-target.inc.c +++ b/tcg/aarch64/tcg-target.inc.c @@ -372,6 +372,7 @@ typedef enum { I3510_EON = 0x4a200000, I3510_ANDS = 0x6a000000, + NOP = 0xd503201f, /* System instructions. */ DMB_ISH = 0xd50338bf, DMB_LD = 0x00000100, @@ -866,10 +867,26 @@ static inline void tcg_out_call(TCGContext *s, tcg_insn_unit *target) void aarch64_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t addr) { tcg_insn_unit *code_ptr = (tcg_insn_unit *)jmp_addr; - tcg_insn_unit *target = (tcg_insn_unit *)addr; + tcg_insn_unit i1, i2; + uint64_t pair; - reloc_pc26_atomic(code_ptr, target); - flush_icache_range(jmp_addr, jmp_addr + 4); + ptrdiff_t offset = addr - jmp_addr; + + if (offset == sextract64(offset, 0, 26)) { + i1 = NOP; + i2 = I3206_B | ((offset >> 2) & 0x3ffffff); + } else { + offset = (addr >> 12) - (jmp_addr >> 12); + + /* patch ADRP */ + i2 = deposit32(*code_ptr++, 29, 2, offset & 0x3); + i2 = deposit32(i2, 5, 19, offset >> 2); + /* patch ADDI */ + i1 = deposit32(*code_ptr, 10, 12, addr & 0xfff); + } + pair = (uint64_t)i1 << 32 | i2; + atomic_set((uint64_t *)jmp_addr, pair); + flush_icache_range(jmp_addr, jmp_addr + 8); } static inline void tcg_out_goto_label(TCGContext *s, TCGLabel *l) @@ -1388,10 +1405,17 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, #endif /* consistency for USE_DIRECT_JUMP */ tcg_debug_assert(s->tb_jmp_insn_offset != NULL); + /* Ensure that ADRP+ADD are 8-byte aligned so that an atomic + write can be used to patch the target address. */ + if ((uintptr_t)s->code_ptr & 7) { + tcg_out32(s, NOP); + } s->tb_jmp_insn_offset[a0] = tcg_current_code_size(s); /* actual branch destination will be patched by - aarch64_tb_set_jmp_target later, beware retranslation. */ - tcg_out_goto_noaddr(s); + aarch64_tb_set_jmp_target later. */ + tcg_out_insn(s, 3406, ADRP, TCG_REG_TMP, 0); + tcg_out_insn(s, 3401, ADDI, TCG_TYPE_I64, TCG_REG_TMP, TCG_REG_TMP, 0); + tcg_out_insn(s, 3207, BR, TCG_REG_TMP); s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s); break;
We use ADRP+ADD to compute the target address for goto_tb. This patch introduces the NOP instruction which is used to align the above instruction pair so that we can use one atomic instruction to patch the destination offsets. CC: Richard Henderson <rth@twiddle.net> CC: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> --- accel/tcg/translate-all.c | 2 +- tcg/aarch64/tcg-target.inc.c | 34 +++++++++++++++++++++++++++++----- 2 files changed, 30 insertions(+), 6 deletions(-)