git: f711d5c3d066 - main - libdtrace: add riscv support
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Date: Mon, 06 Feb 2023 19:28:11 UTC
The branch main has been updated by mhorne:
URL: https://cgit.FreeBSD.org/src/commit/?id=f711d5c3d06677740dc04a0ced27b2bce894bae1
commit f711d5c3d06677740dc04a0ced27b2bce894bae1
Author: Mitchell Horne <mhorne@FreeBSD.org>
AuthorDate: 2023-01-10 15:50:00 +0000
Commit: Mitchell Horne <mhorne@FreeBSD.org>
CommitDate: 2023-02-06 19:26:53 +0000
libdtrace: add riscv support
Largely untested, as we can't really do anything with user probes
without an implementation of fasttrap. However, this is enough to
generate an embedded dtrace program with `dtrace -G` and link the
generated ELF file.
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38301
---
.../opensolaris/lib/libdtrace/common/dt_link.c | 110 +++++++++++++++++++--
1 file changed, 103 insertions(+), 7 deletions(-)
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
index 4e7935250620..51f853d9a2b8 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
@@ -225,9 +225,9 @@ prepare_elf32(dtrace_hdl_t *dtp, const dof_hdr_t *dof, dof_elf32_t *dep)
rel->r_info = ELF32_R_INFO(count + dep->de_global,
R_PPC_REL32);
#elif defined(__riscv)
-/* XXX */
- printf("%s:%s(%d): RISC-V not implemented\n",
- __FUNCTION__, __FILE__, __LINE__);
+ rel->r_offset = s->dofs_offset + dofr[j].dofr_offset;
+ rel->r_info = ELF32_R_INFO(count + dep->de_global,
+ R_RISCV_32_PCREL);
#else
#error unknown ISA
#endif
@@ -403,7 +403,9 @@ prepare_elf64(dtrace_hdl_t *dtp, const dof_hdr_t *dof, dof_elf64_t *dep)
rel->r_info = ELF64_R_INFO(count + dep->de_global,
R_PPC64_REL64);
#elif defined(__riscv)
-/* XXX */
+ rel->r_offset = s->dofs_offset + dofr[j].dofr_offset;
+ rel->r_info = ELF64_R_INFO(count + dep->de_global,
+ R_RISCV_32_PCREL);
#elif defined(__i386) || defined(__amd64)
rel->r_offset = s->dofs_offset +
dofr[j].dofr_offset;
@@ -504,6 +506,22 @@ dump_elf32(dtrace_hdl_t *dtp, const dof_hdr_t *dof, int fd)
elf_file.ehdr.e_machine = EM_386;
#elif defined(__aarch64__)
elf_file.ehdr.e_machine = EM_AARCH64;
+#elif defined(__riscv)
+ elf_file.ehdr.e_machine = EM_RISCV;
+
+ /* Set the ELF flags according to our current ABI */
+#if defined(__riscv_compressed)
+ elf_file.ehdr.e_flags |= EF_RISCV_RVC;
+#endif
+#if defined(__riscv_float_abi_soft)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_SOFT;
+#endif
+#if defined(__riscv_float_abi_single)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_SINGLE;
+#endif
+#if defined(__riscv_float_abi_double)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_DOUBLE;
+#endif
#endif
elf_file.ehdr.e_version = EV_CURRENT;
elf_file.ehdr.e_shoff = sizeof (Elf32_Ehdr);
@@ -645,6 +663,22 @@ dump_elf64(dtrace_hdl_t *dtp, const dof_hdr_t *dof, int fd)
elf_file.ehdr.e_machine = EM_AMD64;
#elif defined(__aarch64__)
elf_file.ehdr.e_machine = EM_AARCH64;
+#elif defined(__riscv)
+ elf_file.ehdr.e_machine = EM_RISCV;
+
+ /* Set the ELF flags according to our current ABI */
+#if defined(__riscv_compressed)
+ elf_file.ehdr.e_flags |= EF_RISCV_RVC;
+#endif
+#if defined(__riscv_float_abi_soft)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_SOFT;
+#endif
+#if defined(__riscv_float_abi_single)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_SINGLE;
+#endif
+#if defined(__riscv_float_abi_double)
+ elf_file.ehdr.e_flags |= EF_RISCV_FLOAT_ABI_DOUBLE;
+#endif
#endif
elf_file.ehdr.e_version = EV_CURRENT;
elf_file.ehdr.e_shoff = sizeof (Elf64_Ehdr);
@@ -917,14 +951,74 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
return (0);
}
#elif defined(__riscv)
+#define DT_OP_NOP 0x00000013 /* addi x0, x0, 0 */
+#define DT_OP_RET 0x00008067 /* jalr x0, x1, 0 */
+#define DT_OP_IS_AUIPC(op) (((op) & 0x7f) == 0x17)
+#define DT_OP_IS_JALR(op) (((op) & 0x707f) == 0x67)
+#define DT_OP_JALR_CALL 0x000080e7 /* jalr x1, x1, 0 */
+#define DT_OP_JALR_TAIL 0x00030067 /* jalr x0, x6, 0 */
#define DT_REL_NONE R_RISCV_NONE
+
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
{
- printf("%s:%s(%d): RISC-V implementation required\n", __FUNCTION__,
- __FILE__, __LINE__);
- return (-1);
+ uint32_t *ip;
+
+ /*
+ * XXX: this implementation is untested, but should serve as a decent
+ * starting point.
+ */
+
+ /*
+ * Ensure that the offset is aligned on a compressed-instruction
+ * boundary.
+ */
+ if ((rela->r_offset & (sizeof (uint16_t) - 1)) != 0)
+ return (-1);
+
+ /*
+ * We only know about some specific relocation types.
+ * We also recognize relocation type NONE, since that gets used for
+ * relocations of USDT probes, and we might be re-processing a file.
+ */
+ if (GELF_R_TYPE(rela->r_info) != R_RISCV_CALL &&
+ GELF_R_TYPE(rela->r_info) != R_RISCV_CALL_PLT &&
+ GELF_R_TYPE(rela->r_info) != R_RISCV_NONE)
+ return (-1);
+
+ ip = (uint32_t *)(p + rela->r_offset);
+
+ /*
+ * We may have already processed this object file in an earlier linker
+ * invocation. Check to see if the present instruction sequence matches
+ * the one we would install below.
+ */
+ if (ip[0] == DT_OP_NOP && (ip[1] == DT_OP_NOP || ip[1] == DT_OP_RET))
+ return (0);
+
+ /*
+ * We expect a auipc+jalr pair, either from a call or a tail.
+ * - call: auipc x1 0; jalr x1, x1, 0
+ * - tail: auipc x6 0; jalr x0, x6, 0
+ */
+ if (!DT_OP_IS_AUIPC(ip[0]) || !DT_OP_IS_JALR(ip[1]))
+ return (-1);
+
+ /*
+ * On riscv, we do not have to differentiate between regular probes and
+ * is-enabled probes. Calls are to be converted into a no-op whereas
+ * tail calls should become a return.
+ */
+ if (ip[1] == DT_OP_JALR_CALL) {
+ ip[0] = DT_OP_NOP;
+ ip[1] = DT_OP_NOP;
+ } else {
+ ip[0] = DT_OP_NOP;
+ ip[1] = DT_OP_RET;
+ }
+
+ return (0);
}
#elif defined(__i386) || defined(__amd64)
@@ -1155,6 +1249,8 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
emachine1 = emachine2 = EM_AMD64;
#elif defined(__aarch64__)
emachine1 = emachine2 = EM_AARCH64;
+#elif defined(__riscv)
+ emachine1 = emachine2 = EM_RISCV;
#endif
symsize = sizeof (Elf64_Sym);
} else {