From patchwork Fri Jan 31 12:11:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej W. 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Rozycki" To: gdb-patches@sourceware.org cc: Jim Wilson , Andrew Burgess , Palmer Dabbelt , Tom Tromey , guoren@kernel.org, lifang_xia@c-sky.com, yunhai_shang@c-sky.com, jiangshuai_li@c-sky.com Subject: [PATCH v3 1/3] RISC-V/Linux/native: Determine FLEN dynamically Message-ID: User-Agent: Alpine 2.21 (LFD 202 2017-01-01) MIME-Version: 1.0 Fix RISC-V native Linux support to handle a 64-bit FPU (FLEN == 64) with both RV32 and RV64 systems, which is a part of the current Linux ABI for hard-float systems, rather than assuming that (FLEN == XLEN) in target description determination and that (FLEN == 64) in register access. We can do better however and not rely on any particular value of FLEN and probe for it dynamically, by observing that the PTRACE_GETREGSET ptrace(2) call will only accept an exact regset size, and that will reflect FLEN. Therefore iterate over the call in target description determination with a geometrically increasing regset size until a match is marked by a successful ptrace(2) call completion or we run beyond the maximum size we can support. Update register accessors accordingly, using FLEN determined to size the buffer used for NT_PRSTATUS requests and then to exchange data with the regcache. Also handle a glibc bug where ELF_NFPREG is defined in terms of NFPREG, however NFPREG is nowhere defined. gdb/ * riscv-linux-nat.c [!NFPREG] (NFPREG): New macro. (supply_fpregset_regnum, fill_fpregset): Handle regset buffer offsets according to FLEN determined. (riscv_linux_nat_target::read_description): Determine FLEN dynamically. (riscv_linux_nat_target::fetch_registers): Size regset buffer according to FLEN determined. (riscv_linux_nat_target::store_registers): Likewise. --- Changes from v2: - Avoid an ambiguous FGR reference in `riscv_linux_nat_target::read_description'. - Advance through the buffer accessed in `supply_fpregset_regnum' and `fill_fpregset' so as to avoid doing a variable multiplication in a loop; also precalculate the buffer offset for single register accesses to avoid excessive line wrapping and improve code readability. - Move the `i' variable declaration to the beginning of `fill_fpregset', for consistency with `supply_fpregset_regnum' (since the loop is being rewritten anyway). Changes from v1: - Also set the size of the regset buffer dynamically in `riscv_linux_nat_target::fetch_registers' and `riscv_linux_nat_target::store_registers', and update `fill_fpregset' and `supply_fpregset_regnum' accordingly. --- gdb/riscv-linux-nat.c | 110 ++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 84 insertions(+), 26 deletions(-) gdb-riscv-linux-nat-flen.diff Index: binutils-gdb/gdb/riscv-linux-nat.c =================================================================== --- binutils-gdb.orig/gdb/riscv-linux-nat.c +++ binutils-gdb/gdb/riscv-linux-nat.c @@ -28,6 +28,11 @@ #include +/* Work around glibc header breakage causing ELF_NFPREG not to be usable. */ +#ifndef NFPREG +# define NFPREG 33 +#endif + /* RISC-V Linux native additions to the default linux support. */ class riscv_linux_nat_target final : public linux_nat_target @@ -88,21 +93,35 @@ static void supply_fpregset_regnum (struct regcache *regcache, const prfpregset_t *fpregs, int regnum) { + int flen = register_size (regcache->arch (), RISCV_FIRST_FP_REGNUM); + union + { + const prfpregset_t *fpregs; + const gdb_byte *buf; + } + fpbuf = { .fpregs = fpregs }; int i; if (regnum == -1) { /* We only support the FP registers and FCSR here. */ - for (i = RISCV_FIRST_FP_REGNUM; i <= RISCV_LAST_FP_REGNUM; i++) - regcache->raw_supply (i, &fpregs->__d.__f[i - RISCV_FIRST_FP_REGNUM]); + for (i = RISCV_FIRST_FP_REGNUM; + i <= RISCV_LAST_FP_REGNUM; + i++, fpbuf.buf += flen) + regcache->raw_supply (i, fpbuf.buf); - regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr); + regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, fpbuf.buf); } else if (regnum >= RISCV_FIRST_FP_REGNUM && regnum <= RISCV_LAST_FP_REGNUM) - regcache->raw_supply (regnum, - &fpregs->__d.__f[regnum - RISCV_FIRST_FP_REGNUM]); + { + fpbuf.buf += flen * (regnum - RISCV_FIRST_FP_REGNUM); + regcache->raw_supply (regnum, fpbuf.buf); + } else if (regnum == RISCV_CSR_FCSR_REGNUM) - regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr); + { + fpbuf.buf += flen * (RISCV_LAST_FP_REGNUM - RISCV_FIRST_FP_REGNUM + 1); + regcache->raw_supply (RISCV_CSR_FCSR_REGNUM, fpbuf.buf); + } } /* Copy all floating point registers from regset FPREGS into REGCACHE. */ @@ -145,19 +164,35 @@ void fill_fpregset (const struct regcache *regcache, prfpregset_t *fpregs, int regnum) { + int flen = register_size (regcache->arch (), RISCV_FIRST_FP_REGNUM); + union + { + prfpregset_t *fpregs; + gdb_byte *buf; + } + fpbuf = { .fpregs = fpregs }; + int i; + if (regnum == -1) { /* We only support the FP registers and FCSR here. */ - for (int i = RISCV_FIRST_FP_REGNUM; i <= RISCV_LAST_FP_REGNUM; i++) - regcache->raw_collect (i, &fpregs->__d.__f[i - RISCV_FIRST_FP_REGNUM]); + for (i = RISCV_FIRST_FP_REGNUM; + i <= RISCV_LAST_FP_REGNUM; + i++, fpbuf.buf += flen) + regcache->raw_collect (i, fpbuf.buf); - regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr); + regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, fpbuf.buf); } else if (regnum >= RISCV_FIRST_FP_REGNUM && regnum <= RISCV_LAST_FP_REGNUM) - regcache->raw_collect (regnum, - &fpregs->__d.__f[regnum - RISCV_FIRST_FP_REGNUM]); + { + fpbuf.buf += flen * (regnum - RISCV_FIRST_FP_REGNUM); + regcache->raw_collect (regnum, fpbuf.buf); + } else if (regnum == RISCV_CSR_FCSR_REGNUM) - regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, &fpregs->__d.__fcsr); + { + fpbuf.buf += flen * (RISCV_LAST_FP_REGNUM - RISCV_FIRST_FP_REGNUM + 1); + regcache->raw_collect (RISCV_CSR_FCSR_REGNUM, fpbuf.buf); + } } /* Return a target description for the current target. */ @@ -166,8 +201,8 @@ const struct target_desc * riscv_linux_nat_target::read_description () { struct riscv_gdbarch_features features; - struct iovec iov; elf_fpregset_t regs; + int flen; int tid; /* Figuring out xlen is easy. */ @@ -175,19 +210,40 @@ riscv_linux_nat_target::read_description tid = inferior_ptid.lwp (); - iov.iov_base = ®s; - iov.iov_len = sizeof (regs); + /* Start with no f-registers. */ + features.flen = 0; - /* Can we fetch the f-registers? */ - if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, - (PTRACE_TYPE_ARG3) &iov) == -1) - features.flen = 0; /* No f-registers. */ - else + /* How much worth of f-registers can we fetch if any? */ + for (flen = sizeof (regs.__f.__f[0]); ; flen *= 2) { - /* TODO: We need a way to figure out the actual length of the - f-registers. We could have 64-bit x-registers, with 32-bit - f-registers. For now, just assumed xlen and flen match. */ - features.flen = features.xlen; + size_t regset_size; + struct iovec iov; + + /* Regsets have a uniform slot size, so we count FSCR like + an FP data register. */ + regset_size = ELF_NFPREG * flen; + if (regset_size > sizeof (regs)) + break; + + iov.iov_base = ®s; + iov.iov_len = regset_size; + if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, + (PTRACE_TYPE_ARG3) &iov) == -1) + { + switch (errno) + { + case EINVAL: + continue; + case EIO: + break; + default: + perror_with_name (_("Couldn't get registers")); + break; + } + } + else + features.flen = flen; + break; } return riscv_create_target_description (features); @@ -228,7 +284,8 @@ riscv_linux_nat_target::fetch_registers elf_fpregset_t regs; iov.iov_base = ®s; - iov.iov_len = sizeof (regs); + iov.iov_len = ELF_NFPREG * register_size (regcache->arch (), + RISCV_FIRST_FP_REGNUM); if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, (PTRACE_TYPE_ARG3) &iov) == -1) @@ -289,7 +346,8 @@ riscv_linux_nat_target::store_registers elf_fpregset_t regs; iov.iov_base = ®s; - iov.iov_len = sizeof (regs); + iov.iov_len = ELF_NFPREG * register_size (regcache->arch (), + RISCV_FIRST_FP_REGNUM); if (ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, (PTRACE_TYPE_ARG3) &iov) == -1)