| Message ID | 20200109160300.26150-45-jthierry@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | objtool: Add support for arm64 | expand |
Hi Julien, On 1/9/20 4:02 PM, Julien Thierry wrote: > This patch implements the functions required to identify and add as > alternatives all the possible destinations of the switch table. > This implementation relies on the new plugin introduced previously which > records information about the switch-table in a > .discard.switch_table_information section. I think you forgot to update the name of the section with respect to what was done in the previous patch (.discard.switch_table_info instead of .discard.switch_table_information). > > Signed-off-by: Raphael Gault <raphael.gault@arm.com> > [J.T.: Update arch implementation to new prototypes, > Update switch table information section name, > Do some clean up, > Use the offset sign information, > Use the newly added rela to find the corresponding jump instruction] > Signed-off-by: Julien Thierry <jthierry@redhat.com> > --- > tools/objtool/arch/arm64/arch_special.c | 251 +++++++++++++++++- > .../objtool/arch/arm64/include/arch_special.h | 2 + > tools/objtool/check.c | 4 +- > tools/objtool/check.h | 2 + > 4 files changed, 255 insertions(+), 4 deletions(-) > > diff --git a/tools/objtool/arch/arm64/arch_special.c b/tools/objtool/arch/arm64/arch_special.c > index 5239489c9c57..a15f6697dc74 100644 > --- a/tools/objtool/arch/arm64/arch_special.c > +++ b/tools/objtool/arch/arm64/arch_special.c > @@ -1,15 +1,262 @@ > // SPDX-License-Identifier: GPL-2.0-or-later > > +#include <stdlib.h> > +#include <string.h> > + > #include "../../special.h" > +#include "../../warn.h" > +#include "arch_special.h" > +#include "bit_operations.h" > +#include "insn_decode.h" > + > +/* > + * The arm64_switch_table_detection_plugin generate an array of elements > + * described by the following structure. > + * Each jump table found in the compilation unit is associated with one of > + * entries of the array. > + */ > +struct switch_table_info { > + u64 switch_table_ref; // Relocation target referencing the beginning of the jump table > + u64 dyn_jump_ref; // Relocation target referencing the set of instructions setting up the jump to the table > + u64 nb_entries; > + u64 offset_unsigned; > +} __attribute__((__packed__)); > + > +static bool insn_is_adr_pcrel(struct instruction *insn) > +{ > + u32 opcode = *(u32 *)(insn->sec->data->d_buf + insn->offset); > + > + return ((opcode >> 24) & 0x1f) == 0x10; > +} > + > +static s64 next_offset(void *table, u8 entry_size, bool is_signed) > +{ > + if (!is_signed) { > + switch (entry_size) { > + case 1: > + return *(u8 *)(table); > + case 2: > + return *(u16 *)(table); > + default: > + return *(u32 *)(table); > + } > + } else { > + switch (entry_size) { > + case 1: > + return *(s8 *)(table); > + case 2: > + return *(s16 *)(table); > + default: > + return *(s32 *)(table); > + } > + } > +} > + > +static u32 get_table_entry_size(u32 insn) > +{ > + unsigned char size = (insn >> 30) & ONES(2); > + > + switch (size) { > + case 0: > + return 1; > + case 1: > + return 2; > + default: > + return 4; > + } > +} > + > +static int add_possible_branch(struct objtool_file *file, > + struct instruction *insn, > + u32 base, s64 offset) > +{ > + struct instruction *dest_insn; > + struct alternative *alt; > + > + offset = base + 4 * offset; > + > + dest_insn = find_insn(file, insn->sec, offset); > + if (!dest_insn) > + return 0; > + > + alt = calloc(1, sizeof(*alt)); > + if (!alt) { > + WARN("allocation failure, can't add jump alternative"); > + return -1; > + } > + > + alt->insn = dest_insn; > + alt->skip_orig = true; > + list_add_tail(&alt->list, &insn->alts); > + return 0; > +} > + > +static struct switch_table_info *get_swt_info(struct section *swt_info_sec, > + struct instruction *insn) > +{ > + u64 *table_ref; > + > + if (!insn->jump_table) { > + WARN("no jump table available for %s+0x%lx", > + insn->sec->name, insn->offset); > + return NULL; > + } > + table_ref = (void *)(swt_info_sec->data->d_buf + > + insn->jump_table->offset); > + return container_of(table_ref, struct switch_table_info, > + switch_table_ref); > +} > + > +static int add_arm64_jump_table_dests(struct objtool_file *file, > + struct instruction *insn) > +{ > + struct switch_table_info *swt_info; > + struct section *objtool_data; > + struct section *rodata_sec; > + struct section *branch_sec; > + struct instruction *pre_jump_insn; > + u8 *switch_table; > + u32 entry_size; > + > + objtool_data = find_section_by_name(file->elf, > + ".discard.switch_table_info"); > + if (!objtool_data) > + return 0; > + > + /* > + * 1. Identify entry for the switch table > + * 2. Retrieve branch instruction > + * 3. Retrieve base offset > + * 3. For all entries in switch table: > + * 3.1. Compute new offset > + * 3.2. Create alternative instruction > + * 3.3. Add alt_instr to insn->alts list > + */ > + swt_info = get_swt_info(objtool_data, insn); > + > + /* retrieving pre jump instruction (ldr) */ > + branch_sec = insn->sec; > + pre_jump_insn = find_insn(file, branch_sec, > + insn->offset - 3 * sizeof(u32)); > + entry_size = get_table_entry_size(*(u32 *)(branch_sec->data->d_buf + > + pre_jump_insn->offset)); > + > + /* retrieving switch table content */ > + rodata_sec = find_section_by_name(file->elf, ".rodata"); > + switch_table = (u8 *)(rodata_sec->data->d_buf + > + insn->jump_table->addend); > + > + /* > + * iterating over the pre-jumps instruction in order to > + * retrieve switch base offset. > + */ > + while (pre_jump_insn && pre_jump_insn->offset <= insn->offset) { > + if (insn_is_adr_pcrel(pre_jump_insn)) { > + u64 base_offset; > + int i; > + > + base_offset = pre_jump_insn->offset + > + pre_jump_insn->immediate; > + > + /* > + * Once we have the switch table entry size > + * we add every possible destination using > + * alternatives of the original branch > + * instruction > + */ > + for (i = 0; i < swt_info->nb_entries; i++) { > + s64 table_offset = next_offset(switch_table, > + entry_size, > + !swt_info->offset_unsigned); > + > + if (add_possible_branch(file, insn, > + base_offset, > + table_offset)) { > + return -1; > + } > + switch_table += entry_size; > + } > + break; > + } > + pre_jump_insn = next_insn_same_sec(file, pre_jump_insn); > + } > + > + return 0; > +} > > int arch_add_jump_table_dests(struct objtool_file *file, > struct instruction *insn) > { > - return 0; > + return add_arm64_jump_table_dests(file, insn); > } > > +static struct rela *find_swt_info_jump_rela(struct section *swt_info_sec, > + u32 index) > +{ > + u32 rela_offset; > + > + rela_offset = index * sizeof(struct switch_table_info) + > + offsetof(struct switch_table_info, dyn_jump_ref); > + return find_rela_by_dest(swt_info_sec, rela_offset); > +} > + > +static struct rela *find_swt_info_table_rela(struct section *swt_info_sec, > + u32 index) > +{ > + u32 rela_offset; > + > + rela_offset = index * sizeof(struct switch_table_info) + > + offsetof(struct switch_table_info, switch_table_ref); > + return find_rela_by_dest(swt_info_sec, rela_offset); > +} > + > +/* > + * Aarch64 jump tables are just arrays of offsets (of varying size/signess) > + * representing the potential destination from a base address loaded by an adr > + * instruction. > + * > + * Aarch64 branches to jump tables are composed of multiple instructions: > + * > + * ldr<?> x_offset, [x_offsets_table, x_index, ...] > + * adr x_dest_base, <addr> > + * add x_dest, x_target_base, x_offset, ... > + * br x_dest > + * > + * The arm64_switch_table_detection_plugin will make the connection between > + * the instruction setting x_offsets_table (dyn_jump_ref) and the actual > + * table of offsets (switch_table_ref) > + */ > struct rela *arch_find_switch_table(struct objtool_file *file, > struct instruction *insn) > { > - return NULL; > + struct section *objtool_data; > + struct rela *res = NULL; > + u32 nb_swt_entries = 0; > + u32 i; > + > + objtool_data = find_section_by_name(file->elf, > + ".discard.switch_table_info"); > + if (objtool_data) > + nb_swt_entries = objtool_data->sh.sh_size / > + sizeof(struct switch_table_info); > + > + for (i = 0; i < nb_swt_entries; i++) { > + struct rela *info_rela; > + > + info_rela = find_swt_info_jump_rela(objtool_data, i); > + if (info_rela && info_rela->sym->sec == insn->sec && > + info_rela->addend == insn->offset) { > + if (res) { > + WARN_FUNC("duplicate objtool_data rela", > + info_rela->sec, info_rela->offset); > + continue; > + } > + res = find_swt_info_table_rela(objtool_data, i); > + if (!res) > + WARN_FUNC("missing relocation in objtool data", > + info_rela->sec, info_rela->offset); > + } > + } > + > + return res; > } > diff --git a/tools/objtool/arch/arm64/include/arch_special.h b/tools/objtool/arch/arm64/include/arch_special.h > index a82a9b3e51df..b96bcee308cf 100644 > --- a/tools/objtool/arch/arm64/include/arch_special.h > +++ b/tools/objtool/arch/arm64/include/arch_special.h > @@ -3,6 +3,8 @@ > #ifndef _ARM64_ARCH_SPECIAL_H > #define _ARM64_ARCH_SPECIAL_H > > +#include <linux/types.h> > + > #define EX_ENTRY_SIZE 8 > #define EX_ORIG_OFFSET 0 > #define EX_NEW_OFFSET 4 > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > index e0c6bda261c8..80ea5bbd36ab 100644 > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -33,8 +33,8 @@ struct instruction *find_insn(struct objtool_file *file, > return NULL; > } > > -static struct instruction *next_insn_same_sec(struct objtool_file *file, > - struct instruction *insn) > +struct instruction *next_insn_same_sec(struct objtool_file *file, > + struct instruction *insn) > { > struct instruction *next = list_next_entry(insn, list); > > diff --git a/tools/objtool/check.h b/tools/objtool/check.h > index 91adec42782c..15165d04d9cb 100644 > --- a/tools/objtool/check.h > +++ b/tools/objtool/check.h > @@ -66,6 +66,8 @@ int check(const char *objname, bool orc); > > struct instruction *find_insn(struct objtool_file *file, > struct section *sec, unsigned long offset); > +struct instruction *next_insn_same_sec(struct objtool_file *file, > + struct instruction *insn); > > #define for_each_insn(file, insn) \ > list_for_each_entry(insn, &file->insn_list, list) > Cheers,
Hi Raphaël, On 1/15/20 4:37 PM, Raphael Gault wrote: > Hi Julien, > > On 1/9/20 4:02 PM, Julien Thierry wrote: >> This patch implements the functions required to identify and add as >> alternatives all the possible destinations of the switch table. >> This implementation relies on the new plugin introduced previously which >> records information about the switch-table in a >> .discard.switch_table_information section. > > I think you forgot to update the name of the section with respect to > what was done in the previous patch (.discard.switch_table_info instead > of .discard.switch_table_information). > Oops, you are correct. Thanks for spotting this. I'll update the commit. Thanks, >> >> Signed-off-by: Raphael Gault <raphael.gault@arm.com> >> [J.T.: Update arch implementation to new prototypes, >> Update switch table information section name, >> Do some clean up, >> Use the offset sign information, >> Use the newly added rela to find the corresponding jump >> instruction] >> Signed-off-by: Julien Thierry <jthierry@redhat.com> >> --- >> tools/objtool/arch/arm64/arch_special.c | 251 +++++++++++++++++- >> .../objtool/arch/arm64/include/arch_special.h | 2 + >> tools/objtool/check.c | 4 +- >> tools/objtool/check.h | 2 + >> 4 files changed, 255 insertions(+), 4 deletions(-) >> >> diff --git a/tools/objtool/arch/arm64/arch_special.c >> b/tools/objtool/arch/arm64/arch_special.c >> index 5239489c9c57..a15f6697dc74 100644 >> --- a/tools/objtool/arch/arm64/arch_special.c >> +++ b/tools/objtool/arch/arm64/arch_special.c >> @@ -1,15 +1,262 @@ >> // SPDX-License-Identifier: GPL-2.0-or-later >> +#include <stdlib.h> >> +#include <string.h> >> + >> #include "../../special.h" >> +#include "../../warn.h" >> +#include "arch_special.h" >> +#include "bit_operations.h" >> +#include "insn_decode.h" >> + >> +/* >> + * The arm64_switch_table_detection_plugin generate an array of elements >> + * described by the following structure. >> + * Each jump table found in the compilation unit is associated with >> one of >> + * entries of the array. >> + */ >> +struct switch_table_info { >> + u64 switch_table_ref; // Relocation target referencing the >> beginning of the jump table >> + u64 dyn_jump_ref; // Relocation target referencing the set of >> instructions setting up the jump to the table >> + u64 nb_entries; >> + u64 offset_unsigned; >> +} __attribute__((__packed__)); >> + >> +static bool insn_is_adr_pcrel(struct instruction *insn) >> +{ >> + u32 opcode = *(u32 *)(insn->sec->data->d_buf + insn->offset); >> + >> + return ((opcode >> 24) & 0x1f) == 0x10; >> +} >> + >> +static s64 next_offset(void *table, u8 entry_size, bool is_signed) >> +{ >> + if (!is_signed) { >> + switch (entry_size) { >> + case 1: >> + return *(u8 *)(table); >> + case 2: >> + return *(u16 *)(table); >> + default: >> + return *(u32 *)(table); >> + } >> + } else { >> + switch (entry_size) { >> + case 1: >> + return *(s8 *)(table); >> + case 2: >> + return *(s16 *)(table); >> + default: >> + return *(s32 *)(table); >> + } >> + } >> +} >> + >> +static u32 get_table_entry_size(u32 insn) >> +{ >> + unsigned char size = (insn >> 30) & ONES(2); >> + >> + switch (size) { >> + case 0: >> + return 1; >> + case 1: >> + return 2; >> + default: >> + return 4; >> + } >> +} >> + >> +static int add_possible_branch(struct objtool_file *file, >> + struct instruction *insn, >> + u32 base, s64 offset) >> +{ >> + struct instruction *dest_insn; >> + struct alternative *alt; >> + >> + offset = base + 4 * offset; >> + >> + dest_insn = find_insn(file, insn->sec, offset); >> + if (!dest_insn) >> + return 0; >> + >> + alt = calloc(1, sizeof(*alt)); >> + if (!alt) { >> + WARN("allocation failure, can't add jump alternative"); >> + return -1; >> + } >> + >> + alt->insn = dest_insn; >> + alt->skip_orig = true; >> + list_add_tail(&alt->list, &insn->alts); >> + return 0; >> +} >> + >> +static struct switch_table_info *get_swt_info(struct section >> *swt_info_sec, >> + struct instruction *insn) >> +{ >> + u64 *table_ref; >> + >> + if (!insn->jump_table) { >> + WARN("no jump table available for %s+0x%lx", >> + insn->sec->name, insn->offset); >> + return NULL; >> + } >> + table_ref = (void *)(swt_info_sec->data->d_buf + >> + insn->jump_table->offset); >> + return container_of(table_ref, struct switch_table_info, >> + switch_table_ref); >> +} >> + >> +static int add_arm64_jump_table_dests(struct objtool_file *file, >> + struct instruction *insn) >> +{ >> + struct switch_table_info *swt_info; >> + struct section *objtool_data; >> + struct section *rodata_sec; >> + struct section *branch_sec; >> + struct instruction *pre_jump_insn; >> + u8 *switch_table; >> + u32 entry_size; >> + >> + objtool_data = find_section_by_name(file->elf, >> + ".discard.switch_table_info"); >> + if (!objtool_data) >> + return 0; >> + >> + /* >> + * 1. Identify entry for the switch table >> + * 2. Retrieve branch instruction >> + * 3. Retrieve base offset >> + * 3. For all entries in switch table: >> + * 3.1. Compute new offset >> + * 3.2. Create alternative instruction >> + * 3.3. Add alt_instr to insn->alts list >> + */ >> + swt_info = get_swt_info(objtool_data, insn); >> + >> + /* retrieving pre jump instruction (ldr) */ >> + branch_sec = insn->sec; >> + pre_jump_insn = find_insn(file, branch_sec, >> + insn->offset - 3 * sizeof(u32)); >> + entry_size = get_table_entry_size(*(u32 *)(branch_sec->data->d_buf + >> + pre_jump_insn->offset)); >> + >> + /* retrieving switch table content */ >> + rodata_sec = find_section_by_name(file->elf, ".rodata"); >> + switch_table = (u8 *)(rodata_sec->data->d_buf + >> + insn->jump_table->addend); >> + >> + /* >> + * iterating over the pre-jumps instruction in order to >> + * retrieve switch base offset. >> + */ >> + while (pre_jump_insn && pre_jump_insn->offset <= insn->offset) { >> + if (insn_is_adr_pcrel(pre_jump_insn)) { >> + u64 base_offset; >> + int i; >> + >> + base_offset = pre_jump_insn->offset + >> + pre_jump_insn->immediate; >> + >> + /* >> + * Once we have the switch table entry size >> + * we add every possible destination using >> + * alternatives of the original branch >> + * instruction >> + */ >> + for (i = 0; i < swt_info->nb_entries; i++) { >> + s64 table_offset = next_offset(switch_table, >> + entry_size, >> + !swt_info->offset_unsigned); >> + >> + if (add_possible_branch(file, insn, >> + base_offset, >> + table_offset)) { >> + return -1; >> + } >> + switch_table += entry_size; >> + } >> + break; >> + } >> + pre_jump_insn = next_insn_same_sec(file, pre_jump_insn); >> + } >> + >> + return 0; >> +} >> int arch_add_jump_table_dests(struct objtool_file *file, >> struct instruction *insn) >> { >> - return 0; >> + return add_arm64_jump_table_dests(file, insn); >> } >> +static struct rela *find_swt_info_jump_rela(struct section >> *swt_info_sec, >> + u32 index) >> +{ >> + u32 rela_offset; >> + >> + rela_offset = index * sizeof(struct switch_table_info) + >> + offsetof(struct switch_table_info, dyn_jump_ref); >> + return find_rela_by_dest(swt_info_sec, rela_offset); >> +} >> + >> +static struct rela *find_swt_info_table_rela(struct section >> *swt_info_sec, >> + u32 index) >> +{ >> + u32 rela_offset; >> + >> + rela_offset = index * sizeof(struct switch_table_info) + >> + offsetof(struct switch_table_info, switch_table_ref); >> + return find_rela_by_dest(swt_info_sec, rela_offset); >> +} >> + >> +/* >> + * Aarch64 jump tables are just arrays of offsets (of varying >> size/signess) >> + * representing the potential destination from a base address loaded >> by an adr >> + * instruction. >> + * >> + * Aarch64 branches to jump tables are composed of multiple >> instructions: >> + * >> + * ldr<?> x_offset, [x_offsets_table, x_index, ...] >> + * adr x_dest_base, <addr> >> + * add x_dest, x_target_base, x_offset, ... >> + * br x_dest >> + * >> + * The arm64_switch_table_detection_plugin will make the connection >> between >> + * the instruction setting x_offsets_table (dyn_jump_ref) and the actual >> + * table of offsets (switch_table_ref) >> + */ >> struct rela *arch_find_switch_table(struct objtool_file *file, >> struct instruction *insn) >> { >> - return NULL; >> + struct section *objtool_data; >> + struct rela *res = NULL; >> + u32 nb_swt_entries = 0; >> + u32 i; >> + >> + objtool_data = find_section_by_name(file->elf, >> + ".discard.switch_table_info"); >> + if (objtool_data) >> + nb_swt_entries = objtool_data->sh.sh_size / >> + sizeof(struct switch_table_info); >> + >> + for (i = 0; i < nb_swt_entries; i++) { >> + struct rela *info_rela; >> + >> + info_rela = find_swt_info_jump_rela(objtool_data, i); >> + if (info_rela && info_rela->sym->sec == insn->sec && >> + info_rela->addend == insn->offset) { >> + if (res) { >> + WARN_FUNC("duplicate objtool_data rela", >> + info_rela->sec, info_rela->offset); >> + continue; >> + } >> + res = find_swt_info_table_rela(objtool_data, i); >> + if (!res) >> + WARN_FUNC("missing relocation in objtool data", >> + info_rela->sec, info_rela->offset); >> + } >> + } >> + >> + return res; >> } >> diff --git a/tools/objtool/arch/arm64/include/arch_special.h >> b/tools/objtool/arch/arm64/include/arch_special.h >> index a82a9b3e51df..b96bcee308cf 100644 >> --- a/tools/objtool/arch/arm64/include/arch_special.h >> +++ b/tools/objtool/arch/arm64/include/arch_special.h >> @@ -3,6 +3,8 @@ >> #ifndef _ARM64_ARCH_SPECIAL_H >> #define _ARM64_ARCH_SPECIAL_H >> +#include <linux/types.h> >> + >> #define EX_ENTRY_SIZE 8 >> #define EX_ORIG_OFFSET 0 >> #define EX_NEW_OFFSET 4 >> diff --git a/tools/objtool/check.c b/tools/objtool/check.c >> index e0c6bda261c8..80ea5bbd36ab 100644 >> --- a/tools/objtool/check.c >> +++ b/tools/objtool/check.c >> @@ -33,8 +33,8 @@ struct instruction *find_insn(struct objtool_file >> *file, >> return NULL; >> } >> -static struct instruction *next_insn_same_sec(struct objtool_file *file, >> - struct instruction *insn) >> +struct instruction *next_insn_same_sec(struct objtool_file *file, >> + struct instruction *insn) >> { >> struct instruction *next = list_next_entry(insn, list); >> diff --git a/tools/objtool/check.h b/tools/objtool/check.h >> index 91adec42782c..15165d04d9cb 100644 >> --- a/tools/objtool/check.h >> +++ b/tools/objtool/check.h >> @@ -66,6 +66,8 @@ int check(const char *objname, bool orc); >> struct instruction *find_insn(struct objtool_file *file, >> struct section *sec, unsigned long offset); >> +struct instruction *next_insn_same_sec(struct objtool_file *file, >> + struct instruction *insn); >> #define for_each_insn(file, insn) \ >> list_for_each_entry(insn, &file->insn_list, list) >> > > Cheers, >
diff --git a/tools/objtool/arch/arm64/arch_special.c b/tools/objtool/arch/arm64/arch_special.c index 5239489c9c57..a15f6697dc74 100644 --- a/tools/objtool/arch/arm64/arch_special.c +++ b/tools/objtool/arch/arm64/arch_special.c @@ -1,15 +1,262 @@ // SPDX-License-Identifier: GPL-2.0-or-later +#include <stdlib.h> +#include <string.h> + #include "../../special.h" +#include "../../warn.h" +#include "arch_special.h" +#include "bit_operations.h" +#include "insn_decode.h" + +/* + * The arm64_switch_table_detection_plugin generate an array of elements + * described by the following structure. + * Each jump table found in the compilation unit is associated with one of + * entries of the array. + */ +struct switch_table_info { + u64 switch_table_ref; // Relocation target referencing the beginning of the jump table + u64 dyn_jump_ref; // Relocation target referencing the set of instructions setting up the jump to the table + u64 nb_entries; + u64 offset_unsigned; +} __attribute__((__packed__)); + +static bool insn_is_adr_pcrel(struct instruction *insn) +{ + u32 opcode = *(u32 *)(insn->sec->data->d_buf + insn->offset); + + return ((opcode >> 24) & 0x1f) == 0x10; +} + +static s64 next_offset(void *table, u8 entry_size, bool is_signed) +{ + if (!is_signed) { + switch (entry_size) { + case 1: + return *(u8 *)(table); + case 2: + return *(u16 *)(table); + default: + return *(u32 *)(table); + } + } else { + switch (entry_size) { + case 1: + return *(s8 *)(table); + case 2: + return *(s16 *)(table); + default: + return *(s32 *)(table); + } + } +} + +static u32 get_table_entry_size(u32 insn) +{ + unsigned char size = (insn >> 30) & ONES(2); + + switch (size) { + case 0: + return 1; + case 1: + return 2; + default: + return 4; + } +} + +static int add_possible_branch(struct objtool_file *file, + struct instruction *insn, + u32 base, s64 offset) +{ + struct instruction *dest_insn; + struct alternative *alt; + + offset = base + 4 * offset; + + dest_insn = find_insn(file, insn->sec, offset); + if (!dest_insn) + return 0; + + alt = calloc(1, sizeof(*alt)); + if (!alt) { + WARN("allocation failure, can't add jump alternative"); + return -1; + } + + alt->insn = dest_insn; + alt->skip_orig = true; + list_add_tail(&alt->list, &insn->alts); + return 0; +} + +static struct switch_table_info *get_swt_info(struct section *swt_info_sec, + struct instruction *insn) +{ + u64 *table_ref; + + if (!insn->jump_table) { + WARN("no jump table available for %s+0x%lx", + insn->sec->name, insn->offset); + return NULL; + } + table_ref = (void *)(swt_info_sec->data->d_buf + + insn->jump_table->offset); + return container_of(table_ref, struct switch_table_info, + switch_table_ref); +} + +static int add_arm64_jump_table_dests(struct objtool_file *file, + struct instruction *insn) +{ + struct switch_table_info *swt_info; + struct section *objtool_data; + struct section *rodata_sec; + struct section *branch_sec; + struct instruction *pre_jump_insn; + u8 *switch_table; + u32 entry_size; + + objtool_data = find_section_by_name(file->elf, + ".discard.switch_table_info"); + if (!objtool_data) + return 0; + + /* + * 1. Identify entry for the switch table + * 2. Retrieve branch instruction + * 3. Retrieve base offset + * 3. For all entries in switch table: + * 3.1. Compute new offset + * 3.2. Create alternative instruction + * 3.3. Add alt_instr to insn->alts list + */ + swt_info = get_swt_info(objtool_data, insn); + + /* retrieving pre jump instruction (ldr) */ + branch_sec = insn->sec; + pre_jump_insn = find_insn(file, branch_sec, + insn->offset - 3 * sizeof(u32)); + entry_size = get_table_entry_size(*(u32 *)(branch_sec->data->d_buf + + pre_jump_insn->offset)); + + /* retrieving switch table content */ + rodata_sec = find_section_by_name(file->elf, ".rodata"); + switch_table = (u8 *)(rodata_sec->data->d_buf + + insn->jump_table->addend); + + /* + * iterating over the pre-jumps instruction in order to + * retrieve switch base offset. + */ + while (pre_jump_insn && pre_jump_insn->offset <= insn->offset) { + if (insn_is_adr_pcrel(pre_jump_insn)) { + u64 base_offset; + int i; + + base_offset = pre_jump_insn->offset + + pre_jump_insn->immediate; + + /* + * Once we have the switch table entry size + * we add every possible destination using + * alternatives of the original branch + * instruction + */ + for (i = 0; i < swt_info->nb_entries; i++) { + s64 table_offset = next_offset(switch_table, + entry_size, + !swt_info->offset_unsigned); + + if (add_possible_branch(file, insn, + base_offset, + table_offset)) { + return -1; + } + switch_table += entry_size; + } + break; + } + pre_jump_insn = next_insn_same_sec(file, pre_jump_insn); + } + + return 0; +} int arch_add_jump_table_dests(struct objtool_file *file, struct instruction *insn) { - return 0; + return add_arm64_jump_table_dests(file, insn); } +static struct rela *find_swt_info_jump_rela(struct section *swt_info_sec, + u32 index) +{ + u32 rela_offset; + + rela_offset = index * sizeof(struct switch_table_info) + + offsetof(struct switch_table_info, dyn_jump_ref); + return find_rela_by_dest(swt_info_sec, rela_offset); +} + +static struct rela *find_swt_info_table_rela(struct section *swt_info_sec, + u32 index) +{ + u32 rela_offset; + + rela_offset = index * sizeof(struct switch_table_info) + + offsetof(struct switch_table_info, switch_table_ref); + return find_rela_by_dest(swt_info_sec, rela_offset); +} + +/* + * Aarch64 jump tables are just arrays of offsets (of varying size/signess) + * representing the potential destination from a base address loaded by an adr + * instruction. + * + * Aarch64 branches to jump tables are composed of multiple instructions: + * + * ldr<?> x_offset, [x_offsets_table, x_index, ...] + * adr x_dest_base, <addr> + * add x_dest, x_target_base, x_offset, ... + * br x_dest + * + * The arm64_switch_table_detection_plugin will make the connection between + * the instruction setting x_offsets_table (dyn_jump_ref) and the actual + * table of offsets (switch_table_ref) + */ struct rela *arch_find_switch_table(struct objtool_file *file, struct instruction *insn) { - return NULL; + struct section *objtool_data; + struct rela *res = NULL; + u32 nb_swt_entries = 0; + u32 i; + + objtool_data = find_section_by_name(file->elf, + ".discard.switch_table_info"); + if (objtool_data) + nb_swt_entries = objtool_data->sh.sh_size / + sizeof(struct switch_table_info); + + for (i = 0; i < nb_swt_entries; i++) { + struct rela *info_rela; + + info_rela = find_swt_info_jump_rela(objtool_data, i); + if (info_rela && info_rela->sym->sec == insn->sec && + info_rela->addend == insn->offset) { + if (res) { + WARN_FUNC("duplicate objtool_data rela", + info_rela->sec, info_rela->offset); + continue; + } + res = find_swt_info_table_rela(objtool_data, i); + if (!res) + WARN_FUNC("missing relocation in objtool data", + info_rela->sec, info_rela->offset); + } + } + + return res; } diff --git a/tools/objtool/arch/arm64/include/arch_special.h b/tools/objtool/arch/arm64/include/arch_special.h index a82a9b3e51df..b96bcee308cf 100644 --- a/tools/objtool/arch/arm64/include/arch_special.h +++ b/tools/objtool/arch/arm64/include/arch_special.h @@ -3,6 +3,8 @@ #ifndef _ARM64_ARCH_SPECIAL_H #define _ARM64_ARCH_SPECIAL_H +#include <linux/types.h> + #define EX_ENTRY_SIZE 8 #define EX_ORIG_OFFSET 0 #define EX_NEW_OFFSET 4 diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e0c6bda261c8..80ea5bbd36ab 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -33,8 +33,8 @@ struct instruction *find_insn(struct objtool_file *file, return NULL; } -static struct instruction *next_insn_same_sec(struct objtool_file *file, - struct instruction *insn) +struct instruction *next_insn_same_sec(struct objtool_file *file, + struct instruction *insn) { struct instruction *next = list_next_entry(insn, list); diff --git a/tools/objtool/check.h b/tools/objtool/check.h index 91adec42782c..15165d04d9cb 100644 --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -66,6 +66,8 @@ int check(const char *objname, bool orc); struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset); +struct instruction *next_insn_same_sec(struct objtool_file *file, + struct instruction *insn); #define for_each_insn(file, insn) \ list_for_each_entry(insn, &file->insn_list, list)