perf: Fix segbase for ld.lld linked objects

PATCH Superseded Fangrui Song 2 participants 4 messages May 27, 2022 perf events

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Fangrui Song

author

2022-05-27 05:52 UTC #0 lore raw

PATCH 1/1 perf: Fix segbase for ld.lld linked objects

segbase is the address of .eh_frame_hdr and table_data is segbase plus the header size. find_proc_info computes segbase as map->start + segbase - map->pgoff which is wrong when

* .eh_frame_hdr and .text are in different PT_LOAD program headers
* and their p_vaddr difference does not equal their p_offset difference

Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has such R and RX PT_LOAD program headers.

ld.lld => fail
ld.lld --no-rosegment => ok
ld.lld -z separate-code => ok

ld.bfd -z separate-code (default for Linux/x86) => ok ld.bfd -z noseparate-code => ok

To fix the issue, compute segbase as dso's base address plus PT_GNU_EH_FRAME's p_vaddr.

Reported-by Sebastian Ullrich <[email protected]>

Link https://github.com/ClangBuiltLinux/linux/issues/1646

Signed-off-by Fangrui Song <[email protected]>

Cc Ian Rogers <[email protected]>

---
 tools/perf/util/dso.h                    |  2 +
 tools/perf/util/unwind-libunwind-local.c | 96 ++++++++++++++++--------
 2 files changed, 67 insertions(+), 31 deletions(-)

tools/perf/util/dso.h +2 -0

index 3a9fd4d389b5..ec4fc1a9454b 100644
@@ -179,6 +179,7 @@ struct dso {
 	bool		 loaded;
 	u8		 rel;
 	struct build_id	 bid;
+	u64		 base_addr;
 	u64		 text_offset;
 	const char	 *short_name;
 	const char	 *long_name;

@@ -197,6 +198,7 @@ struct dso {
 		u64		 file_size;
 		struct list_head open_entry;
 		u64		 debug_frame_offset;
+		u64		 eh_frame_hdr_addr;
 		u64		 eh_frame_hdr_offset;
 	} data;
 	/* bpf prog information */

tools/perf/util/unwind-libunwind-local.c +65 ~~-31~~

152 lines not on this page · raw message

Signature · 1 line

2.36.1.124.g0e6072fb45-goog

Ian Rogers

reviewer Tested-by on v1 1/1

2022-05-27 06:49 UTC #1 lore raw

Quoted 18 lines · Fangrui Song

segbase is the address of .eh_frame_hdr and table_data is segbase plus the header size. find_proc_info computes segbase as map->start + segbase - map->pgoff which is wrong when
* .eh_frame_hdr and .text are in different PT_LOAD program headers
* and their p_vaddr difference does not equal their p_offset difference
Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has such R and RX PT_LOAD program headers.
ld.lld => fail
ld.lld --no-rosegment => ok
ld.lld -z separate-code => ok
ld.bfd -z separate-code (default for Linux/x86) => ok ld.bfd -z noseparate-code => ok

Quoted 7 lines

To fix the issue, compute segbase as dso's base address plus PT_GNU_EH_FRAME's p_vaddr.
Reported-by Sebastian Ullrich <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1646
Signed-off-by Fangrui Song <[email protected]>
Cc Ian Rogers <[email protected]>

Thanks Fangrui! I tested static vs not, bfd and lld, perf test and some hand tests. I couldn't see anything out of order. The code looks good although there could be some ambiguity over the variables ending _addr as these are the ELF given addresses rather than the thread's virtual memory addresses. I'm also trying to get more comments especially on major data structures like dso, but that can be fixed as a follow-on.

Tested-by Ian Rogers <[email protected]>

Quoted 188 lines

---
 tools/perf/util/dso.h                    |  2 +
 tools/perf/util/unwind-libunwind-local.c | 96 ++++++++++++++++--------
 2 files changed, 67 insertions(+), 31 deletions(-)

tools/perf/util/dso.h +2 -0

index 3a9fd4d389b5..ec4fc1a9454b 100644
@@ -179,6 +179,7 @@ struct dso {
        bool             loaded;
        u8               rel;
        struct build_id  bid;
+       u64              base_addr;
        u64              text_offset;
        const char       *short_name;
        const char       *long_name;

@@ -197,6 +198,7 @@ struct dso {
                u64              file_size;
                struct list_head open_entry;
                u64              debug_frame_offset;
+               u64              eh_frame_hdr_addr;
                u64              eh_frame_hdr_offset;
        } data;
        /* bpf prog information */

tools/perf/util/unwind-libunwind-local.c +65 ~~-32~~

index 41e29fc7648a..7a0053954e49 100644
@@ -169,30 +169,55 @@ static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
        __v;                                                    \
        })
 
-static u64 elf_section_offset(int fd, const char *name)
+static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
 {
        Elf *elf;
        GElf_Ehdr ehdr;
        GElf_Shdr shdr;
-       u64 offset = 0;
+       int ret;
 
        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
-               return 0;
+               return -1;
 
-       do {
-               if (gelf_getehdr(elf, &ehdr) == NULL)
-                       break;
+       if (gelf_getehdr(elf, &ehdr) == NULL)
+               goto out_err;
 
-               if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
-                       break;
-
-               offset = shdr.sh_offset;
-       } while (0);
+       if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
+               goto out_err;
 
+       *address = shdr.sh_addr;
+       *offset = shdr.sh_offset;
+       ret = 0;
+out_err:
        elf_end(elf);
+       return ret;
+}
+
+#ifndef NO_LIBUNWIND_DEBUG_FRAME
+static u64 elf_section_offset(int fd, const char *name)
+{
+       u64 address, offset;
+
+       if (elf_section_address_and_offset(fd, name, &address, &offset))
+               return 0;
+
        return offset;
 }
+#endif
+
+static int elf_base_address(int fd)
+{
+       Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+       GElf_Phdr phdr;
+       int retval = 0;
+
+       if (gelf_getphdr(elf, 0, &phdr) != NULL)
+               retval = phdr.p_vaddr & -getpagesize();
+
+       elf_end(elf);
+       return retval;
+}
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 static int elf_is_exec(int fd, const char *name)

@@ -248,8 +273,7 @@ struct eh_frame_hdr {
 } __packed;
 
 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
-                              u64 offset, u64 *table_data, u64 *segbase,
-                              u64 *fde_count)
+                              u64 offset, u64 *table_data_offset, u64 *fde_count)
 {
        struct eh_frame_hdr hdr;
        u8 *enc = (u8 *) &hdr.enc;

@@ -265,35 +289,45 @@ static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
        dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 
        *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
-       *segbase    = offset;
-       *table_data = (enc - (u8 *) &hdr) + offset;
+       *table_data_offset = enc - (u8 *) &hdr;
        return 0;
 }
 
-static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
+static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
                                     u64 *table_data, u64 *segbase,
                                     u64 *fde_count)
 {
-       int ret = -EINVAL, fd;
-       u64 offset = dso->data.eh_frame_hdr_offset;
+       struct map *map;
+       int ret, fd;
 
-       if (offset == 0) {
-               fd = dso__data_get_fd(dso, machine);
+       if (dso->data.eh_frame_hdr_offset == 0) {
+               u64 addr_min = UINT64_MAX;
+
+               fd = dso__data_get_fd(dso, ui->machine);
                if (fd < 0)
                        return -EINVAL;
 
                /* Check the .eh_frame section for unwinding info */
-               offset = elf_section_offset(fd, ".eh_frame_hdr");
-               dso->data.eh_frame_hdr_offset = offset;
+               ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
+                                                    &dso->data.eh_frame_hdr_addr,
+                                                    &dso->data.eh_frame_hdr_offset);
+               maps__for_each_entry(ui->thread->maps, map) {
+                       if (map->dso == dso && map->start < addr_min)
+                               addr_min = map->start;
+               }
+               dso->base_addr = addr_min - elf_base_address(fd);
                dso__data_put_fd(dso);
+               if (ret || dso->data.eh_frame_hdr_offset == 0)
+                   return -EINVAL;
        }
 
-       if (offset)
-               ret = unwind_spec_ehframe(dso, machine, offset,
-                                         table_data, segbase,
-                                         fde_count);
-
-       return ret;
+       *segbase = dso->base_addr + dso->data.eh_frame_hdr_addr;
+       ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
+                                  table_data, fde_count);
+       if (ret)
+           return ret;
+       *table_data += *segbase;
+       return 0;
 }
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME

@@ -388,14 +422,14 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
        pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 
        /* Check the .eh_frame section for unwinding info */
-       if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
+       if (!read_unwind_spec_eh_frame(map->dso, ui,
                                       &table_data, &segbase, &fde_count)) {
                memset(&di, 0, sizeof(di));
                di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
                di.start_ip = map->start;
                di.end_ip   = map->end;
-               di.u.rti.segbase    = map->start + segbase - map->pgoff;
-               di.u.rti.table_data = map->start + table_data - map->pgoff;
+               di.u.rti.segbase    = segbase;
+               di.u.rti.table_data = table_data;
                di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
                                      / sizeof(unw_word_t);
                ret = dwarf_search_unwind_table(as, ip, &di, pi,
--

2.36.1.124.g0e6072fb45-goog

Ian Rogers

reviewer

2022-05-27 16:04 UTC #2 lore raw

Quoted 43 lines · Ian Rogers

Quoted 18 lines · Fangrui Song
segbase is the address of .eh_frame_hdr and table_data is segbase plus the header size. find_proc_info computes segbase as map->start + segbase - map->pgoff which is wrong when
* .eh_frame_hdr and .text are in different PT_LOAD program headers
* and their p_vaddr difference does not equal their p_offset difference
Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has such R and RX PT_LOAD program headers.
ld.lld => fail
ld.lld --no-rosegment => ok
ld.lld -z separate-code => ok
ld.bfd -z separate-code (default for Linux/x86) => ok ld.bfd -z noseparate-code => ok
Quoted 7 lines
To fix the issue, compute segbase as dso's base address plus PT_GNU_EH_FRAME's p_vaddr.
Reported-by Sebastian Ullrich <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1646
Signed-off-by Fangrui Song <[email protected]>
Cc Ian Rogers <[email protected]>
Thanks Fangrui! I tested static vs not, bfd and lld, perf test and some hand tests. I couldn't see anything out of order. The code looks good although there could be some ambiguity over the variables ending _addr as these are the ELF given addresses rather than the thread's virtual memory addresses. I'm also trying to get more comments especially on major data structures like dso, but that can be fixed as a follow-on.
Tested-by Ian Rogers <[email protected]>
Quoted 5 lines
---
 tools/perf/util/dso.h                    |  2 +
 tools/perf/util/unwind-libunwind-local.c | 96 ++++++++++++++++--------
 2 files changed, 67 insertions(+), 31 deletions(-)

Quoted 9 lines

tools/perf/util/dso.h struct dso { · line 182

Quoted 9 lines

tools/perf/util/dso.h +1 -0

index 3a9fd4d389b5..ec4fc1a9454b 100644
@@ -179,6 +179,7 @@ struct dso {
        bool             loaded;
        u8               rel;
        struct build_id  bid;
+       u64              base_addr;

This is an address in a thread, as one dso can be shared by multiple threads/processes it seems unsafe to hold it as the dso may be loaded at a different address in a different thread. For now we can just recompute the value rather than store it in the dso.

Quoted 8 lines

tools/perf/util/dso.h struct dso { · line 201

Quoted 8 lines

tools/perf/util/dso.h +1 -0

        u64              text_offset;
        const char       *short_name;
        const char       *long_name;

@@ -197,6 +198,7 @@ struct dso {
                u64              file_size;
                struct list_head open_entry;
                u64              debug_frame_offset;
+               u64              eh_frame_hdr_addr;

This is the elf section address and safe to hold here.

Thanks,
Ian

Quoted 166 lines

tools/perf/util/dso.h +0 -0

                u64              eh_frame_hdr_offset;
        } data;
        /* bpf prog information */

tools/perf/util/unwind-libunwind-local.c +65 ~~-32~~

index 41e29fc7648a..7a0053954e49 100644
@@ -169,30 +169,55 @@ static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
        __v;                                                    \
        })
 
-static u64 elf_section_offset(int fd, const char *name)
+static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
 {
        Elf *elf;
        GElf_Ehdr ehdr;
        GElf_Shdr shdr;
-       u64 offset = 0;
+       int ret;
 
        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
-               return 0;
+               return -1;
 
-       do {
-               if (gelf_getehdr(elf, &ehdr) == NULL)
-                       break;
+       if (gelf_getehdr(elf, &ehdr) == NULL)
+               goto out_err;
 
-               if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
-                       break;
-
-               offset = shdr.sh_offset;
-       } while (0);
+       if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
+               goto out_err;
 
+       *address = shdr.sh_addr;
+       *offset = shdr.sh_offset;
+       ret = 0;
+out_err:
        elf_end(elf);
+       return ret;
+}
+
+#ifndef NO_LIBUNWIND_DEBUG_FRAME
+static u64 elf_section_offset(int fd, const char *name)
+{
+       u64 address, offset;
+
+       if (elf_section_address_and_offset(fd, name, &address, &offset))
+               return 0;
+
        return offset;
 }
+#endif
+
+static int elf_base_address(int fd)
+{
+       Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+       GElf_Phdr phdr;
+       int retval = 0;
+
+       if (gelf_getphdr(elf, 0, &phdr) != NULL)
+               retval = phdr.p_vaddr & -getpagesize();
+
+       elf_end(elf);
+       return retval;
+}
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 static int elf_is_exec(int fd, const char *name)

@@ -248,8 +273,7 @@ struct eh_frame_hdr {
 } __packed;
 
 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
-                              u64 offset, u64 *table_data, u64 *segbase,
-                              u64 *fde_count)
+                              u64 offset, u64 *table_data_offset, u64 *fde_count)
 {
        struct eh_frame_hdr hdr;
        u8 *enc = (u8 *) &hdr.enc;

@@ -265,35 +289,45 @@ static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
        dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 
        *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
-       *segbase    = offset;
-       *table_data = (enc - (u8 *) &hdr) + offset;
+       *table_data_offset = enc - (u8 *) &hdr;
        return 0;
 }
 
-static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
+static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
                                     u64 *table_data, u64 *segbase,
                                     u64 *fde_count)
 {
-       int ret = -EINVAL, fd;
-       u64 offset = dso->data.eh_frame_hdr_offset;
+       struct map *map;
+       int ret, fd;
 
-       if (offset == 0) {
-               fd = dso__data_get_fd(dso, machine);
+       if (dso->data.eh_frame_hdr_offset == 0) {
+               u64 addr_min = UINT64_MAX;
+
+               fd = dso__data_get_fd(dso, ui->machine);
                if (fd < 0)
                        return -EINVAL;
 
                /* Check the .eh_frame section for unwinding info */
-               offset = elf_section_offset(fd, ".eh_frame_hdr");
-               dso->data.eh_frame_hdr_offset = offset;
+               ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
+                                                    &dso->data.eh_frame_hdr_addr,
+                                                    &dso->data.eh_frame_hdr_offset);
+               maps__for_each_entry(ui->thread->maps, map) {
+                       if (map->dso == dso && map->start < addr_min)
+                               addr_min = map->start;
+               }
+               dso->base_addr = addr_min - elf_base_address(fd);
                dso__data_put_fd(dso);
+               if (ret || dso->data.eh_frame_hdr_offset == 0)
+                   return -EINVAL;
        }
 
-       if (offset)
-               ret = unwind_spec_ehframe(dso, machine, offset,
-                                         table_data, segbase,
-                                         fde_count);
-
-       return ret;
+       *segbase = dso->base_addr + dso->data.eh_frame_hdr_addr;
+       ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
+                                  table_data, fde_count);
+       if (ret)
+           return ret;
+       *table_data += *segbase;
+       return 0;
 }
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME

@@ -388,14 +422,14 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
        pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 
        /* Check the .eh_frame section for unwinding info */
-       if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
+       if (!read_unwind_spec_eh_frame(map->dso, ui,
                                       &table_data, &segbase, &fde_count)) {
                memset(&di, 0, sizeof(di));
                di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
                di.start_ip = map->start;
                di.end_ip   = map->end;
-               di.u.rti.segbase    = map->start + segbase - map->pgoff;
-               di.u.rti.table_data = map->start + table_data - map->pgoff;
+               di.u.rti.segbase    = segbase;
+               di.u.rti.table_data = table_data;
                di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
                                      / sizeof(unw_word_t);
                ret = dwarf_search_unwind_table(as, ip, &di, pi,
--

2.36.1.124.g0e6072fb45-goog

Fangrui Song

author

2022-05-27 18:35 UTC #3 lore raw

Quoted 44 lines · Ian Rogers

Quoted 43 lines · Ian Rogers
Quoted 18 lines · Fangrui Song
segbase is the address of .eh_frame_hdr and table_data is segbase plus the header size. find_proc_info computes segbase as map->start + segbase - map->pgoff which is wrong when
* .eh_frame_hdr and .text are in different PT_LOAD program headers
* and their p_vaddr difference does not equal their p_offset difference
Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has such R and RX PT_LOAD program headers.
ld.lld => fail
ld.lld --no-rosegment => ok
ld.lld -z separate-code => ok
ld.bfd -z separate-code (default for Linux/x86) => ok ld.bfd -z noseparate-code => ok
Quoted 7 lines
To fix the issue, compute segbase as dso's base address plus PT_GNU_EH_FRAME's p_vaddr.
Reported-by Sebastian Ullrich <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1646
Signed-off-by Fangrui Song <[email protected]>
Cc Ian Rogers <[email protected]>
Thanks Fangrui! I tested static vs not, bfd and lld, perf test and some hand tests. I couldn't see anything out of order. The code looks good although there could be some ambiguity over the variables ending _addr as these are the ELF given addresses rather than the thread's virtual memory addresses. I'm also trying to get more comments especially on major data structures like dso, but that can be fixed as a follow-on.
Tested-by Ian Rogers <[email protected]>
Quoted 5 lines
---
 tools/perf/util/dso.h                    |  2 +
 tools/perf/util/unwind-libunwind-local.c | 96 ++++++++++++++++--------
 2 files changed, 67 insertions(+), 31 deletions(-)

Quoted 14 lines

Quoted 9 lines
tools/perf/util/dso.h struct dso { · line 182
Quoted 9 lines
tools/perf/util/dso.h +1 -0
index 3a9fd4d389b5..ec4fc1a9454b 100644
@@ -179,6 +179,7 @@ struct dso {
        bool             loaded;
        u8               rel;
        struct build_id  bid;
+       u64              base_addr;
This is an address in a thread, as one dso can be shared by multiple threads/processes it seems unsafe to hold it as the dso may be loaded at a different address in a different thread. For now we can just recompute the value rather than store it in the dso.

Ack. Thanks for spotting the issue!
I did not know that dso can be shared (read the code for the first time), guessing this is why dso__data_get_fd(dso, ui->machine); needs a lock.

Quoted 10 lines

Quoted 8 lines

tools/perf/util/dso.h struct dso { · line 201

Quoted 8 lines

tools/perf/util/dso.h +1 -0

        u64              text_offset;
        const char       *short_name;
        const char       *long_name;

@@ -197,6 +198,7 @@ struct dso {
                u64              file_size;
                struct list_head open_entry;
                u64              debug_frame_offset;
+               u64              eh_frame_hdr_addr;

This is the elf section address and safe to hold here.

Ack.

Fixed in PATCH v2
https://lore.kernel.org/linux-perf-users/[email protected]/T/#u

Quoted 169 lines

Thanks,
Ian

Quoted 166 lines

tools/perf/util/dso.h +0 -0

                u64              eh_frame_hdr_offset;
        } data;
        /* bpf prog information */

tools/perf/util/unwind-libunwind-local.c +65 ~~-32~~

index 41e29fc7648a..7a0053954e49 100644
@@ -169,30 +169,55 @@ static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
        __v;                                                    \
        })
 
-static u64 elf_section_offset(int fd, const char *name)
+static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
 {
        Elf *elf;
        GElf_Ehdr ehdr;
        GElf_Shdr shdr;
-       u64 offset = 0;
+       int ret;
 
        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
-               return 0;
+               return -1;
 
-       do {
-               if (gelf_getehdr(elf, &ehdr) == NULL)
-                       break;
+       if (gelf_getehdr(elf, &ehdr) == NULL)
+               goto out_err;
 
-               if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
-                       break;
-
-               offset = shdr.sh_offset;
-       } while (0);
+       if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
+               goto out_err;
 
+       *address = shdr.sh_addr;
+       *offset = shdr.sh_offset;
+       ret = 0;
+out_err:
        elf_end(elf);
+       return ret;
+}
+
+#ifndef NO_LIBUNWIND_DEBUG_FRAME
+static u64 elf_section_offset(int fd, const char *name)
+{
+       u64 address, offset;
+
+       if (elf_section_address_and_offset(fd, name, &address, &offset))
+               return 0;
+
        return offset;
 }
+#endif
+
+static int elf_base_address(int fd)
+{
+       Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+       GElf_Phdr phdr;
+       int retval = 0;
+
+       if (gelf_getphdr(elf, 0, &phdr) != NULL)
+               retval = phdr.p_vaddr & -getpagesize();
+
+       elf_end(elf);
+       return retval;
+}
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 static int elf_is_exec(int fd, const char *name)

@@ -248,8 +273,7 @@ struct eh_frame_hdr {
 } __packed;
 
 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
-                              u64 offset, u64 *table_data, u64 *segbase,
-                              u64 *fde_count)
+                              u64 offset, u64 *table_data_offset, u64 *fde_count)
 {
        struct eh_frame_hdr hdr;
        u8 *enc = (u8 *) &hdr.enc;

@@ -265,35 +289,45 @@ static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
        dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
 
        *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
-       *segbase    = offset;
-       *table_data = (enc - (u8 *) &hdr) + offset;
+       *table_data_offset = enc - (u8 *) &hdr;
        return 0;
 }
 
-static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
+static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
                                     u64 *table_data, u64 *segbase,
                                     u64 *fde_count)
 {
-       int ret = -EINVAL, fd;
-       u64 offset = dso->data.eh_frame_hdr_offset;
+       struct map *map;
+       int ret, fd;
 
-       if (offset == 0) {
-               fd = dso__data_get_fd(dso, machine);
+       if (dso->data.eh_frame_hdr_offset == 0) {
+               u64 addr_min = UINT64_MAX;
+
+               fd = dso__data_get_fd(dso, ui->machine);
                if (fd < 0)
                        return -EINVAL;
 
                /* Check the .eh_frame section for unwinding info */
-               offset = elf_section_offset(fd, ".eh_frame_hdr");
-               dso->data.eh_frame_hdr_offset = offset;
+               ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
+                                                    &dso->data.eh_frame_hdr_addr,
+                                                    &dso->data.eh_frame_hdr_offset);
+               maps__for_each_entry(ui->thread->maps, map) {
+                       if (map->dso == dso && map->start < addr_min)
+                               addr_min = map->start;
+               }
+               dso->base_addr = addr_min - elf_base_address(fd);
                dso__data_put_fd(dso);
+               if (ret || dso->data.eh_frame_hdr_offset == 0)
+                   return -EINVAL;
        }
 
-       if (offset)
-               ret = unwind_spec_ehframe(dso, machine, offset,
-                                         table_data, segbase,
-                                         fde_count);
-
-       return ret;
+       *segbase = dso->base_addr + dso->data.eh_frame_hdr_addr;
+       ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
+                                  table_data, fde_count);
+       if (ret)
+           return ret;
+       *table_data += *segbase;
+       return 0;
 }
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME

@@ -388,14 +422,14 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
        pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 
        /* Check the .eh_frame section for unwinding info */
-       if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
+       if (!read_unwind_spec_eh_frame(map->dso, ui,
                                       &table_data, &segbase, &fde_count)) {
                memset(&di, 0, sizeof(di));
                di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
                di.start_ip = map->start;
                di.end_ip   = map->end;
-               di.u.rti.segbase    = map->start + segbase - map->pgoff;
-               di.u.rti.table_data = map->start + table_data - map->pgoff;
+               di.u.rti.segbase    = segbase;
+               di.u.rti.table_data = table_data;
                di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
                                      / sizeof(unw_word_t);
                ret = dwarf_search_unwind_table(as, ip, &di, pi,
--

2.36.1.124.g0e6072fb45-goog