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bpf, bpftool: Fix incorrect disasm pc

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[ Upstream commit 4d99e509c161f8610de125202c648fa4acd00541 ]

This patch addresses the bpftool issue "Wrong callq address displayed"[0].

The issue stemmed from an incorrect program counter (PC) value used during
disassembly with LLVM or libbfd.

For LLVM: The PC argument must represent the actual address in the kernel
to compute the correct relative address.

For libbfd: The relative address can be adjusted by adding func_ksym within
the custom info->print_address_func to yield the correct address.

Links:
[0] https://github.com/libbpf/bpftool/issues/109

Changes:
v2 -> v3:
  * Address comment from Quentin:
    * Remove the typedef.

v1 -> v2:
  * Fix the broken libbfd disassembler.

Fixes: e1947c750f ("bpftool: Refactor disassembler for JIT-ed programs")
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Quentin Monnet <qmo@kernel.org>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20241031152844.68817-1-leon.hwang@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Leon Hwang
2024-10-31 23:28:44 +08:00
committed by Greg Kroah-Hartman
parent b32f915fc6
commit 41f0b320b6
1 changed files with 29 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
tools/bpf/bpftool/jit_disasm.c
View File

@@ -80,7 +80,8 @@ symbol_lookup_callback(__maybe_unused void *disasm_info,
static int
init_context(disasm_ctx_t *ctx, const char *arch,
__maybe_unused const char *disassembler_options,
__maybe_unused unsigned char *image, __maybe_unused ssize_t len)
__maybe_unused unsigned char *image, __maybe_unused ssize_t len,
__maybe_unused __u64 func_ksym)
{
char *triple;
@@ -109,12 +110,13 @@ static void destroy_context(disasm_ctx_t *ctx)
}
static int
disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc)
disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc,
__u64 func_ksym)
{
char buf[256];
int count;
count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, pc,
count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, func_ksym + pc,
buf, sizeof(buf));
if (json_output)
printf_json(buf);
@@ -136,8 +138,21 @@ int disasm_init(void)
#ifdef HAVE_LIBBFD_SUPPORT
#define DISASM_SPACER "\t"
struct disasm_info {
struct disassemble_info info;
__u64 func_ksym;
};
static void disasm_print_addr(bfd_vma addr, struct disassemble_info *info)
{
struct disasm_info *dinfo = container_of(info, struct disasm_info, info);
addr += dinfo->func_ksym;
generic_print_address(addr, info);
}
typedef struct {
struct disassemble_info *info;
struct disasm_info *info;
disassembler_ftype disassemble;
bfd *bfdf;
} disasm_ctx_t;
@@ -215,7 +230,7 @@ static int fprintf_json_styled(void *out,
static int init_context(disasm_ctx_t *ctx, const char *arch,
const char *disassembler_options,
unsigned char *image, ssize_t len)
unsigned char *image, ssize_t len, __u64 func_ksym)
{
struct disassemble_info *info;
char tpath[PATH_MAX];
@@ -238,12 +253,13 @@ static int init_context(disasm_ctx_t *ctx, const char *arch,
}
bfdf = ctx->bfdf;
ctx->info = malloc(sizeof(struct disassemble_info));
ctx->info = malloc(sizeof(struct disasm_info));
if (!ctx->info) {
p_err("mem alloc failed");
goto err_close;
}
info = ctx->info;
ctx->info->func_ksym = func_ksym;
info = &ctx->info->info;
if (json_output)
init_disassemble_info_compat(info, stdout,
@@ -272,6 +288,7 @@ static int init_context(disasm_ctx_t *ctx, const char *arch,
info->disassembler_options = disassembler_options;
info->buffer = image;
info->buffer_length = len;
info->print_address_func = disasm_print_addr;
disassemble_init_for_target(info);
@@ -304,9 +321,10 @@ static void destroy_context(disasm_ctx_t *ctx)
static int
disassemble_insn(disasm_ctx_t *ctx, __maybe_unused unsigned char *image,
__maybe_unused ssize_t len, int pc)
__maybe_unused ssize_t len, int pc,
__maybe_unused __u64 func_ksym)
{
return ctx->disassemble(pc, ctx->info);
return ctx->disassemble(pc, &ctx->info->info);
}
int disasm_init(void)
@@ -331,7 +349,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
if (!len)
return -1;
if (init_context(&ctx, arch, disassembler_options, image, len))
if (init_context(&ctx, arch, disassembler_options, image, len, func_ksym))
return -1;
if (json_output)
@@ -360,7 +378,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
printf("%4x:" DISASM_SPACER, pc);
}
count = disassemble_insn(&ctx, image, len, pc);
count = disassemble_insn(&ctx, image, len, pc, func_ksym);
if (json_output) {
/* Operand array, was started in fprintf_json. Before